简介

Redis 是一个开源（BSD许可）的内存中的数据结构存储系统，基于C语言开发，它可以用作数据库、缓存和消息中间件。 相比于传统的关系型数据库，Redis的存储方式是key-value型的，说到key-value，我们肯定能想到JSON，但是JSON中value是不区分数据类型的，Redis支持多种类型的数据结构，如 字符串（strings）， 散列（hashes）， 列表（lists）， 集合（sets）， 有序集合（sorted sets） 与范围查询， bitmaps， hyperloglogs 和 地理空间（geospatial） 索引半径查询，能够更好的帮助我们进行数据的存储检索。此外Redis 内置了 复制（replication），LUA脚本（Lua scripting）， LRU驱动事件（LRU eviction），事务（transactions） 和不同级别的 磁盘持久化（persistence）， 并通过 Redis哨兵（Sentinel）和自动 分区（Cluster）提供高可用性（high availability）。

Redis可以作为缓存来使用，也可以用作NoSQL数据库，有着丰富的数据类型，不同的数据类型适应的场景也各不相同。

• String：缓存、计数器、分布式锁等。
• List：链表、队列、微博关注人时间轴列表等。
• Hash：用户信息、Hash 表等。
• Set：去重、赞、踩、共同好友等。
• Zset：访问量排行榜、点击量排行榜等。

官方网站：https://redis.io

为什么使用

为什么会诞生Redis呢？任何一种技术的产生本身都是为了解决问题。

计算机中数据文件主要存储在磁盘上，磁盘在结构上每一面包含很多磁道，每个磁磁道又按照512字节等分为多个扇区，操作系统在实际读取文件的时候都是以block为单位（扇区的整数倍）进行读取的，随着文件变大，速度会越慢，磁盘IO会成为瓶颈。关系型数据库的出现是为了改善磁盘IO的瓶颈，但整体而言，磁盘IO和数据库的IO总量是相等的，因此出现了了索引的概念，如果没有索引，仅仅只是建了数据库和表，不会有太大帮助，依旧很慢，如MySQL的索引，在读取数据时索引被加载进内存，大大提高了数据定位的速度。而Redis是基于内存进行存储的，磁盘的寻址是ms级别，而内存的寻址级别是ns级别的，因此使用Redis在很大程度上可以解决IO瓶颈，非常适合用户规模体量大的网站以及高并发、高性能低延迟的场景。

关于数据库特性分析：https://db-engines.com/en/ranking
关于Redis性能测试报告：https://redis.com/wp-content/uploads/2021/09/NoSQL-Benchmark.pdf

安装

关于安装就不在赘述，这里简单介绍两种安装方式。

Ubuntu环境安装

使用的Ubuntu环境是20.04LTS桌面版本。由于其软件源已经包含了Redis，因此可以使用apt命令快捷安装。

sudo apt install redis-server

安装完成后会自动启动，查看Redis状态。

starsray@starsray:/opt/docker/redis$ sudo systemctl status redis-server
● redis-server.service - Advanced key-value store
   Loaded: loaded (/lib/systemd/system/redis-server.service; enabled; vendor preset: enabled)
   Active: active (running) since Sat 2022-03-12 16:01:23 CST; 23s ago
     Docs: http://redis.io/documentation,
           man:redis-server(1)
 Main PID: 10098 (redis-server)
    Tasks: 4 (limit: 4915)
   Memory: 1.9M
   CGroup: /system.slice/redis-server.service
           └─10098 /usr/bin/redis-server 127.0.0.1:6379

基本安装就完成了，关于Redis的配置在后面再进行描述。

Docker安装

拉取镜像

使用docker安装Redis首先需要获取Redis的镜像，如果没有指定tag，默认使用的是latest版本。

docker pull redis

也可以搜索Redis镜像，从仓库中选择自己想要使用的镜像。

docker search redis

但是docker search出来的结果是不同镜像的latest版本，如果想使用某个镜像的历史版本，可以使用下面的脚本来查询。

sudo mkdir -p /opt/script
sudo tee /opt/script/docker-search-tag.sh <<-'EOF'
#!/bin/sh
#
# Simple script that will display docker repository tags.
#
# Usage:
#   $ docker-show-repo-tags.sh ubuntu centos
for Repo in $* ; do
  curl -s -S "https://registry.hub.docker.com/v2/repositories/library/$Repo/tags/" | \
    sed -e 's/,/,\n/g' -e 's/\[/\[\n/g' | \
    grep '"name"' | \
    awk -F\" '{print $4;}' | \
    sort -fu | \
    sed -e "s/^/${Repo}:/"
done
EOF

授予脚本可执行权限，并且添加软连接到可执行目录

sudo chmod +x docker-search-tag.sh
sudo ln -s /opt/script/docker-search-tag.sh /usr/local/bin/

使用添加的脚本命令搜索Redis镜像tag列表，相关tag都被展示出来了。

starsray@starsray:/usr/bin$ docker-search-tag.sh redis
redis:6.2
redis:6.2.6
redis:6.2.6-bullseye
redis:6.2-bullseye
redis:7.0-rc
redis:7.0-rc2
redis:7.0-rc2-bullseye
redis:7.0-rc-bullseye
redis:bullseye
redis:latest

启动容器

首先获取官网Redis配置，方便随时更改容器中的Redis参数。这里使用docker-compose来配置Redis启动参数。

version: '3'
services:
  redis_compose:
    restart: always
    image: redis:latest
    container_name: redis
    ports:
      - 6379:6379
    volumes:
      - ./data:/data
      - ./logs:/logs  
      - ./conf/redis.conf:/etc/redis/redis.conf
    command:
      redis-server /etc/redis/redis.conf --requirepass "yourpassword"

通过volumes分别挂载Redis的配置、数据、日志目录，使用Redis-server指定配置文件的方式来启动服务端。如果不需要设置密码可以不配置requirepass。
启动成功后使用一个可视化工具来链接，推荐一个官方工具Redislnsight。

• 官方网址
• 下载地址

工具界面，支持命令行CLI，支持主题选择，支持界面化操作等等功能。

命令行工具

Redis相比于其他缓存技术，有一个明显的优势就是其包含了数据类型，数据类型的好处在于在更新数据时可以精准定位，操作效率高。redis-cli提供了一个非常友好的提示界面，通过help命令可以查看各种命令的使用及简介。

127.0.0.1:53954> help
redis-cli 5.0.7
To get help about Redis commands type:
      "help @<group>" to get a list of commands in <group>
      "help <command>" for help on <command>
      "help <tab>" to get a list of possible help topics
      "quit" to exit
To set redis-cli preferences:
      ":set hints" enable online hints
      ":set nohints" disable online hints
Set your preferences in ~/.redisclirc

help @表示一个分组的命令集合。例如查看String类型下面包含的命令。

127.0.0.1:53954> help @string
  BITCOUNT key [start end]
  summary: Count set bits in a string
  since: 2.6.0
  BITPOS key bit [start] [end]
  summary: Find first bit set or clear in a string
  since: 2.8.7
  ......

help 用来查看一个具体命令的使用及介绍。

127.0.0.1:53954> help set
  SET key value [expiration EX seconds|PX milliseconds] [NX|XX]
  summary: Set the string value of a key
  since: 1.0.0
  group: string

对象与数据类型

Redis自己封装实现了一些基本的数据类型，从面向对象的角度来说更应该称其为对象类型，这也就是我们常说的String、List、Hash、Set、ZSet等，Redis在实现这些数据类型的时候也是用了诸如SDS、链表、跳跃表等数据结构，了解这些数据结构的实现和特性，对于使用Redis所提供的数据类型会更加的得心应手，接下来这部分会从Redis中用到的数据结构，以及数据结构在不同数据类型中的应用来展示说明。

基本数据结构

SDS

SRedis基于C语言开发，但是并没有直接调用C的字符串，而是通过C语言实现了自身的动态字符串SDS（Simple Dynamic Strings），其内部定义了一个C结构体。

struct sdshdr {
    int len;
    int free;
    char buf[];
};

• 记录buf中已使用字节数量，等于SDS保存字符串的长度
• 记录buf中未使用字节的数量
• 存储字符串的字节数组，Redis是二进制安全的，基于其保存形式

SDS可以说是Redis中最核心的一个实现库了，引用作者的一段原话描述，并且SDS已经作为一个单独的项目被维护。

SDS was a C string I developed in the past for my everyday C programming needs, later it was moved into Redis where it is used extensively and where it was modified in order to be suitable for high performance operations. Now it was extracted from Redis and forked as a stand alone project.

Redis作为一个K-V数据库，包含了几种基本的数据类型，其中K的实现都是以SDS为基础的字符串，其他几种数据类型，如Hash、Set、List这些本身更像是一种数据结构，其内部的元素也都是以SDS为基础的数据形式存储，因此深入理解SDS就很有必要。下面就从几个方面来剖析SDS与C字符串的区别与特性。

1. 常数复杂度获取字符串的长度

在C中如何表示一个字符串，一般采用N+1的形式来表示，所谓N+1指的是，使用长度为N的数组以及结束字符’\0’来表示一个字符串。因此在获取字符串的长度时候需要通过遍历循环的方式直到遇到字符串’\0’结束确定长度，需要的时间复杂度为O(N)。

由于SDS存储了字符串的长度，因此获取字符串的长度只需要访问属性就能获取，需要的时间复杂度为O(1)，在字符串较短的时候这种优势可能不明显，在字符串较长时这种优势就体现出来了。

SDS在设置和更新的时候都会重新计算字符串的长度更新len和free的值，调用者无需关心，也不用手动修改。因此在Redis中无论怎样去获取字符串的长度都不会有性能方面的问题，可以直接获取长度。

1. 杜绝缓冲区内存溢出

在C语言中字符串的拼接可以使用strcat函数来实现。
语法/原型：

char*strcat(char* strDestination, const char* strSource);

strcat函数把 strSource 所指向的字符串追加到 strDestination 所指向的字符串的结尾，必须要保strDestination 有足够的内存空间来容纳两个字符串，否则会导致溢出错误。
参数说明：

• strDestination：目的字符串；
• strSource：源字符串。

注意：strDestination 末尾的\0会被覆盖，strSource 末尾的\0会一起被复制过去，最终的字符串只有一个\0。
返回值：指向 strDestination 的指针。

内存中紧邻着存放着两个字符串S1、S2，如果此时执行strcat函数将S’拼接到S1后面，会导致S1的内存溢出到S2的空间。
SDS同样提供了字符串拼接的sdscat函数，与C中strcat所不同的是SDS字符串在拼接时会有自己的空间分配策略，会先检查现有字符串的空间是否满足需求，如果不满足先进行扩容然后在进行实际的操作，这样就避免了内存溢出的情况。

1. 减少字符串更新内存重新分配的次数

C字符串中没有记录自身的长度，也没有设置缓冲区，每次对字符串的增长或者缩短都要重新进行内存的分配，尤其是对于高性能、高并发的B/S架构来说，这种频繁的内存分配会是相当大的一部分开支（涉及复杂算法甚至执行系统调用内核状态切换），为了解决这些问题，SDS在内存空间分配的过程中提供了两种优化策略：

• 空间预分配：用于优化字符串的增长操作，SDS对字符串的预分配空间大小不会超过1M，这个限制由SDS_MAX_PREALLOC来确定，也可以修改。当预分配空间小于1M时，执行的实际分配大小是所需大小的2倍，也就是在分配空间后，sdshdr的len和free属性会相等，如果实际所需空间大于1M，那么程序会多分配1M的未使用空间，也就是free部分空间为1M。
• 空间惰性释放：这个策略主要针对字符串的缩短操作，Redis作为一个高效的缓存数据库，实际生产中面临着严苛的读写环境，由于字符串总是会频繁的被操作，因此当字符串长度变短后，SDS并不会立即回收这部分空闲的空间，而是使用free进行记录，等待使用或者时机来释放空间。

1. 二进制安全

所谓二进制安全，是一种主要用于字符串操作函数相关的计算机编程术语。一个二进制安全功能（函数），其本质上将操作输入作为原始的、无任何特殊格式意义的数据流。其在操作上应包含一个字符所能有的256种可能的值（假设为8位字符）。
这也说明了只关心存储不关心格式，但在C字符串中，存储字符必须以某种编码格式进行储存，由于C以’\0’来表示结尾，这种有特殊意义结尾的字符就带来了不安全，如果存储的字符串或二进制流包含空格，数据将会被截断，这中限制使得C字符串不能存储图片、音视频等文件。
如果有一种特殊的使用空格来分割字符串的形式，那么这种结构就不适合用C字符串来保存。如下图所示在读取Hello Redis的时候，在读取完Hello后就不在进行，忽略掉Redis。

SDS所提供的API都是二进制安全的，这也正式buf为字节数组的原因，Redis不是用数组来保存字符，而是来保存一系列二进制位的，因此也可以用来保存图片、音视频等数据，在读取和存储时数据一致，无关乎语言、序列化等因素限制。

1. 兼容部分C字符串函数

SDS所提供的API都是二进制安全的，并且为了兼容部分C函数，也遵循了末尾为空字符串结尾的习惯，这样就可以使得SDS在保存文本时也可以调用C中string.h库定义的函数，这样也避免了重复区造轮子。

String是Redis中使用最广泛的基本数据类型，一个key所对应的Value最大值为512M，再加上二进制安全，因此可以用来存储图片等其他非结构化的数据。此外对于String，redis还内置了三种编码格式int、embstr和raw，根据其存入值的长短或实际类型而定。

• int：存储的值必须为整数类型，当数字在0~9999之间时，由于redis在启动时会创建10000个共享对象，所以在存值的时候如果在此数值之间则会将该键的引用指向该共享对象；需要注意的是当通过配置文件参数 maxmemory 设置了 Redis 可用的最大空间大小时，Redis不会使用共享对象，因为对于每一个键值都需要使用一个 redisObject 来记录其LRU信息。
• embstr：适用于当存入的值小于等于44个字节的字符串。

• raw：存入的字符串超过44个字节时将转换为raw编码，但当内部编码为embstr的键值对使用append 命令对值进行修改时，无论当前字符串的长度为多少，其内部编码都将转换为raw。

  链表

  链表作为一种常用的数据结构，提供了高效的节点重排能力以及顺序性的节点访问方式，并且可以通过增删节点来调整长度，不同于数组，链表对内存没有严格的要求，可以分布在各个地方，通过指针寻找下一个节点。
  
  链表在不同的语言中都有实现，例如Java中的LinkedList，但是C语言并没有内置这种结构，因此Redis自己实现了这种结构并应用在各种地方，如列表List、以及发布订阅、慢查询、监视器等功能。
  Redis中链表使用的是双向链表，所谓双向链表，每个节点中包含prev、next两个指针以及值value信息，这种结构更加方便数据的读取。Redis中的链表节点使用listNode结构体来表示。

  typedef struct listNode {
    struct listNode *prev;
    struct listNode *next;
    void        *value;
  } listNode;

  使用listNode就可以组成链表结构，但是Redis又使用list来进行封装，操作链表会更加方便。

  typedef struct list
  {
    listNode    *head;
    listNode    *tail;
    void *(*dup)(void *ptr);
    void (*free)( void *ptr );
    int (*match)( void *ptr, void *key );
    unsigned long len;
  } list;

• head 头节点

• tail 尾节点
• dup 复制链表节点中保存的值
• free 释放链表节点中保存的值
• match 比对链表节点的值和另一个输入值是否相等
• len 链表长度计数器

如图所示使用list来保存一个包含三个listNode结构的链表：

Redis中的链表特性可以总结为如下几点：

• listNode
  • 双端：链表节点包含prev、next指针，获取前置节点和后置节点复杂度为O(1)，操作快。
  • 无欢：prev、next的指向都是NULL，可以以此为链表终点。
• list
  • head/tail：list结构包含head和tail，获取链表的头节点和尾节点的复杂度为O(1)。
  • len：存储链表的长度，获取链表长度的复杂度为O(1)。
  • 多态：链表节点使用void*指针保存节点值，并且可以使用dup、free、match三个属性为节点设置类型特定函数，所以链表可以用来保存不同类型的值。

    跳跃表

对象类型

String

List

Hash

Set

Sorted Set

配置详解

Redis配置文件redis.conf指定了很多配置项，对其中常用的配置进行解释，所用到的配置文件与上面官网推荐的一致。

# Redis configuration file example.
# redis的启动需要读取指定路径的配置文件redis.conf
# Note that in order to read the configuration file, Redis must be
# started with the file path as first argument:
# 
# ./redis-server /path/to/redis.conf
# 当内存需要特殊指定大小时候，redis可以用一种通用的方式来指定内存，例如1k,5GB,或者4M,并且使用这种方式大小写不敏感。
# Note on units: when memory size is needed, it is possible to specify
# it in the usual form of 1k 5GB 4M and so forth:
# 
# 1k => 1000 bytes
# 1kb => 1024 bytes
# 1m => 1000000 bytes
# 1mb => 1024*1024 bytes
# 1g => 1000000000 bytes
# 1gb => 1024*1024*1024 bytes
#
# units are case insensitive so 1GB 1Gb 1gB are all the same.
################################## INCLUDES ###################################
# include可以用来引入一些其他配置文件，类似于spring cloud config引入公共配置的作用，
# 需要注意的是include不会被来自admin或Redis Sentinel的“CONFIG REWRITE”重写，如果有相同
# 的配置项，redis总是会使用最后一次配置的值，如果为了避免配置被覆盖掉最好把include放在配置文
# 件的开始，相反如果需要include来覆盖配置，直接把它放在配置文件的末尾。
# 
# Include one or more other config files here.  This is useful if you
# have a standard template that goes to all Redis servers but also need
# to customize a few per-server settings.  Include files can include
# other files, so use this wisely.
#
# Note that option "include" won't be rewritten by command "CONFIG REWRITE"
# from admin or Redis Sentinel. Since Redis always uses the last processed
# line as value of a configuration directive, you'd better put includes
# at the beginning of this file to avoid overwriting config change at runtime.
#
# If instead you are interested in using includes to override configuration
# options, it is better to use include as the last line.
# 
# include /path/to/local.conf
# include /path/to/other.conf
################################## MODULES #####################################
# Load modules at startup. If the server is not able to load modules
# it will abort. It is possible to use multiple loadmodule directives.
#
# loadmodule /path/to/my_module.so
# loadmodule /path/to/other_module.so
################################## NETWORK #####################################
# By default, if no "bind" configuration directive is specified, Redis listens
# for connections from all available network interfaces on the host machine.
# It is possible to listen to just one or multiple selected interfaces using
# the "bind" configuration directive, followed by one or more IP addresses.
# Each address can be prefixed by "-", which means that redis will not fail to
# start if the address is not available. Being not available only refers to
# addresses that does not correspond to any network interfece. Addresses that
# are already in use will always fail, and unsupported protocols will always BE
# silently skipped.
#
# Examples:
#
# bind 192.168.1.100 10.0.0.1     # listens on two specific IPv4 addresses
# bind 127.0.0.1 ::1              # listens on loopback IPv4 and IPv6
# bind * -::*                     # like the default, all available interfaces
#
# ~~~ WARNING ~~~ If the computer running Redis is directly exposed to the
# internet, binding to all the interfaces is dangerous and will expose the
# instance to everybody on the internet. So by default we uncomment the
# following bind directive, that will force Redis to listen only on the
# IPv4 and IPv6 (if available) loopback interface addresses (this means Redis
# will only be able to accept client connections from the same host that it is
# running on).
#
# IF YOU ARE SURE YOU WANT YOUR INSTANCE TO LISTEN TO ALL THE INTERFACES
# JUST COMMENT OUT THE FOLLOWING LINE.
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
# bind 127.0.0.1 -::1
# Protected mode is a layer of security protection, in order to avoid that
# Redis instances left open on the internet are accessed and exploited.
#
# When protected mode is on and if:
#
# 1) The server is not binding explicitly to a set of addresses using the
#    "bind" directive.
# 2) No password is configured.
#
# The server only accepts connections from clients connecting from the
# IPv4 and IPv6 loopback addresses 127.0.0.1 and ::1, and from Unix domain
# sockets.
#
# By default protected mode is enabled. You should disable it only if
# you are sure you want clients from other hosts to connect to Redis
# even if no authentication is configured, nor a specific set of interfaces
# are explicitly listed using the "bind" directive.
protected-mode no
# Accept connections on the specified port, default is 6379 (IANA #815344).
# If port 0 is specified Redis will not listen on a TCP socket.
port 6379
# TCP listen() backlog.
#
# In high requests-per-second environments you need a high backlog in order
# to avoid slow clients connection issues. Note that the Linux kernel
# will silently truncate it to the value of /proc/sys/net/core/somaxconn so
# make sure to raise both the value of somaxconn and tcp_max_syn_backlog
# in order to get the desired effect.
tcp-backlog 511
# Unix socket.
#
# Specify the path for the Unix socket that will be used to listen for
# incoming connections. There is no default, so Redis will not listen
# on a unix socket when not specified.
#
# unixsocket /run/redis.sock
# unixsocketperm 700
# Close the connection after a client is idle for N seconds (0 to disable)
timeout 0
# TCP keepalive.
#
# If non-zero, use SO_KEEPALIVE to send TCP ACKs to clients in absence
# of communication. This is useful for two reasons:
#
# 1) Detect dead peers.
# 2) Force network equipment in the middle to consider the connection to be
#    alive.
#
# On Linux, the specified value (in seconds) is the period used to send ACKs.
# Note that to close the connection the double of the time is needed.
# On other kernels the period depends on the kernel configuration.
#
# A reasonable value for this option is 300 seconds, which is the new
# Redis default starting with Redis 3.2.1.
tcp-keepalive 300
################################# TLS/SSL #####################################
# By default, TLS/SSL is disabled. To enable it, the "tls-port" configuration
# directive can be used to define TLS-listening ports. To enable TLS on the
# default port, use:
#
# port 0
# tls-port 6379
# Configure a X.509 certificate and private key to use for authenticating the
# server to connected clients, masters or cluster peers.  These files should be
# PEM formatted.
#
# tls-cert-file redis.crt 
# tls-key-file redis.key
#
# If the key file is encrypted using a passphrase, it can be included here
# as well.
#
# tls-key-file-pass secret
# Normally Redis uses the same certificate for both server functions (accepting
# connections) and client functions (replicating from a master, establishing
# cluster bus connections, etc.).
#
# Sometimes certificates are issued with attributes that designate them as
# client-only or server-only certificates. In that case it may be desired to use
# different certificates for incoming (server) and outgoing (client)
# connections. To do that, use the following directives:
#
# tls-client-cert-file client.crt
# tls-client-key-file client.key
#
# If the key file is encrypted using a passphrase, it can be included here
# as well.
#
# tls-client-key-file-pass secret
# Configure a DH parameters file to enable Diffie-Hellman (DH) key exchange:
#
# tls-dh-params-file redis.dh
# Configure a CA certificate(s) bundle or directory to authenticate TLS/SSL
# clients and peers.  Redis requires an explicit configuration of at least one
# of these, and will not implicitly use the system wide configuration.
#
# tls-ca-cert-file ca.crt
# tls-ca-cert-dir /etc/ssl/certs
# By default, clients (including replica servers) on a TLS port are required
# to authenticate using valid client side certificates.
#
# If "no" is specified, client certificates are not required and not accepted.
# If "optional" is specified, client certificates are accepted and must be
# valid if provided, but are not required.
#
# tls-auth-clients no
# tls-auth-clients optional
# By default, a Redis replica does not attempt to establish a TLS connection
# with its master.
#
# Use the following directive to enable TLS on replication links.
#
# tls-replication yes
# By default, the Redis Cluster bus uses a plain TCP connection. To enable
# TLS for the bus protocol, use the following directive:
#
# tls-cluster yes
# By default, only TLSv1.2 and TLSv1.3 are enabled and it is highly recommended
# that older formally deprecated versions are kept disabled to reduce the attack surface.
# You can explicitly specify TLS versions to support.
# Allowed values are case insensitive and include "TLSv1", "TLSv1.1", "TLSv1.2",
# "TLSv1.3" (OpenSSL >= 1.1.1) or any combination.
# To enable only TLSv1.2 and TLSv1.3, use:
#
# tls-protocols "TLSv1.2 TLSv1.3"
# Configure allowed ciphers.  See the ciphers(1ssl) manpage for more information
# about the syntax of this string.
#
# Note: this configuration applies only to <= TLSv1.2.
#
# tls-ciphers DEFAULT:!MEDIUM
# Configure allowed TLSv1.3 ciphersuites.  See the ciphers(1ssl) manpage for more
# information about the syntax of this string, and specifically for TLSv1.3
# ciphersuites.
#
# tls-ciphersuites TLS_CHACHA20_POLY1305_SHA256
# When choosing a cipher, use the server's preference instead of the client
# preference. By default, the server follows the client's preference.
#
# tls-prefer-server-ciphers yes
# By default, TLS session caching is enabled to allow faster and less expensive
# reconnections by clients that support it. Use the following directive to disable
# caching.
#
# tls-session-caching no
# Change the default number of TLS sessions cached. A zero value sets the cache
# to unlimited size. The default size is 20480.
#
# tls-session-cache-size 5000
# Change the default timeout of cached TLS sessions. The default timeout is 300
# seconds.
#
# tls-session-cache-timeout 60
################################# GENERAL #####################################
# By default Redis does not run as a daemon. Use 'yes' if you need it.
# Note that Redis will write a pid file in /var/run/redis.pid when daemonized.
# When Redis is supervised by upstart or systemd, this parameter has no impact.
daemonize no
# If you run Redis from upstart or systemd, Redis can interact with your
# supervision tree. Options:
#   supervised no      - no supervision interaction
#   supervised upstart - signal upstart by putting Redis into SIGSTOP mode
#                        requires "expect stop" in your upstart job config
#   supervised systemd - signal systemd by writing READY=1 to $NOTIFY_SOCKET
#                        on startup, and updating Redis status on a regular
#                        basis.
#   supervised auto    - detect upstart or systemd method based on
#                        UPSTART_JOB or NOTIFY_SOCKET environment variables
# Note: these supervision methods only signal "process is ready."
#       They do not enable continuous pings back to your supervisor.
#
# The default is "no". To run under upstart/systemd, you can simply uncomment
# the line below:
#
# supervised auto
# If a pid file is specified, Redis writes it where specified at startup
# and removes it at exit.
#
# When the server runs non daemonized, no pid file is created if none is
# specified in the configuration. When the server is daemonized, the pid file
# is used even if not specified, defaulting to "/var/run/redis.pid".
#
# Creating a pid file is best effort: if Redis is not able to create it
# nothing bad happens, the server will start and run normally.
#
# Note that on modern Linux systems "/run/redis.pid" is more conforming
# and should be used instead.
pidfile /var/run/redis_6379.pid
# Specify the server verbosity level.
# This can be one of:
# debug (a lot of information, useful for development/testing)
# verbose (many rarely useful info, but not a mess like the debug level)
# notice (moderately verbose, what you want in production probably)
# warning (only very important / critical messages are logged)
loglevel notice
# Specify the log file name. Also the empty string can be used to force
# Redis to log on the standard output. Note that if you use standard
# output for logging but daemonize, logs will be sent to /dev/null
logfile ""
# To enable logging to the system logger, just set 'syslog-enabled' to yes,
# and optionally update the other syslog parameters to suit your needs.
# syslog-enabled no
# Specify the syslog identity.
# syslog-ident redis
# Specify the syslog facility. Must be USER or between LOCAL0-LOCAL7.
# syslog-facility local0
# To disable the built in crash log, which will possibly produce cleaner core
# dumps when they are needed, uncomment the following:
#
# crash-log-enabled no
# To disable the fast memory check that's run as part of the crash log, which
# will possibly let redis terminate sooner, uncomment the following:
#
# crash-memcheck-enabled no
# Set the number of databases. The default database is DB 0, you can select
# a different one on a per-connection basis using SELECT <dbid> where
# dbid is a number between 0 and 'databases'-1
databases 16
# By default Redis shows an ASCII art logo only when started to log to the
# standard output and if the standard output is a TTY and syslog logging is
# disabled. Basically this means that normally a logo is displayed only in
# interactive sessions.
#
# However it is possible to force the pre-4.0 behavior and always show a
# ASCII art logo in startup logs by setting the following option to yes.
always-show-logo no
# By default, Redis modifies the process title (as seen in 'top' and 'ps') to
# provide some runtime information. It is possible to disable this and leave
# the process name as executed by setting the following to no.
set-proc-title yes
# When changing the process title, Redis uses the following template to construct
# the modified title.
#
# Template variables are specified in curly brackets. The following variables are
# supported:
#
# {title}           Name of process as executed if parent, or type of child process.
# {listen-addr}     Bind address or '*' followed by TCP or TLS port listening on, or
#                   Unix socket if only that's available.
# {server-mode}     Special mode, i.e. "[sentinel]" or "[cluster]".
# {port}            TCP port listening on, or 0.
# {tls-port}        TLS port listening on, or 0.
# {unixsocket}      Unix domain socket listening on, or "".
# {config-file}     Name of configuration file used.
#
proc-title-template "{title} {listen-addr} {server-mode}"
################################ SNAPSHOTTING  ################################
# Save the DB to disk.
#
# save <seconds> <changes>
#
# Redis will save the DB if both the given number of seconds and the given
# number of write operations against the DB occurred.
#
# Snapshotting can be completely disabled with a single empty string argument
# as in following example:
#
# save ""
#
# Unless specified otherwise, by default Redis will save the DB:
#   * After 3600 seconds (an hour) if at least 1 key changed
#   * After 300 seconds (5 minutes) if at least 100 keys changed
#   * After 60 seconds if at least 10000 keys changed
#
# You can set these explicitly by uncommenting the three following lines.
#
# save 3600 1
# save 300 100
# save 60 10000
# By default Redis will stop accepting writes if RDB snapshots are enabled
# (at least one save point) and the latest background save failed.
# This will make the user aware (in a hard way) that data is not persisting
# on disk properly, otherwise chances are that no one will notice and some
# disaster will happen.
#
# If the background saving process will start working again Redis will
# automatically allow writes again.
#
# However if you have setup your proper monitoring of the Redis server
# and persistence, you may want to disable this feature so that Redis will
# continue to work as usual even if there are problems with disk,
# permissions, and so forth.
stop-writes-on-bgsave-error yes
# Compress string objects using LZF when dump .rdb databases?
# By default compression is enabled as it's almost always a win.
# If you want to save some CPU in the saving child set it to 'no' but
# the dataset will likely be bigger if you have compressible values or keys.
rdbcompression yes
# Since version 5 of RDB a CRC64 checksum is placed at the end of the file.
# This makes the format more resistant to corruption but there is a performance
# hit to pay (around 10%) when saving and loading RDB files, so you can disable it
# for maximum performances.
#
# RDB files created with checksum disabled have a checksum of zero that will
# tell the loading code to skip the check.
rdbchecksum yes
# Enables or disables full sanitation checks for ziplist and listpack etc when
# loading an RDB or RESTORE payload. This reduces the chances of a assertion or
# crash later on while processing commands.
# Options:
#   no         - Never perform full sanitation
#   yes        - Always perform full sanitation
#   clients    - Perform full sanitation only for user connections.
#                Excludes: RDB files, RESTORE commands received from the master
#                connection, and client connections which have the
#                skip-sanitize-payload ACL flag.
# The default should be 'clients' but since it currently affects cluster
# resharding via MIGRATE, it is temporarily set to 'no' by default.
#
# sanitize-dump-payload no
# The filename where to dump the DB
dbfilename dump.rdb
# Remove RDB files used by replication in instances without persistence
# enabled. By default this option is disabled, however there are environments
# where for regulations or other security concerns, RDB files persisted on
# disk by masters in order to feed replicas, or stored on disk by replicas
# in order to load them for the initial synchronization, should be deleted
# ASAP. Note that this option ONLY WORKS in instances that have both AOF
# and RDB persistence disabled, otherwise is completely ignored.
#
# An alternative (and sometimes better) way to obtain the same effect is
# to use diskless replication on both master and replicas instances. However
# in the case of replicas, diskless is not always an option.
rdb-del-sync-files no
# The working directory.
#
# The DB will be written inside this directory, with the filename specified
# above using the 'dbfilename' configuration directive.
#
# The Append Only File will also be created inside this directory.
#
# Note that you must specify a directory here, not a file name.
dir ./
################################# REPLICATION #################################
# Master-Replica replication. Use replicaof to make a Redis instance a copy of
# another Redis server. A few things to understand ASAP about Redis replication.
#
#   +------------------+      +---------------+
#   |      Master      | ---> |    Replica    |
#   | (receive writes) |      |  (exact copy) |
#   +------------------+      +---------------+
#
# 1) Redis replication is asynchronous, but you can configure a master to
#    stop accepting writes if it appears to be not connected with at least
#    a given number of replicas.
# 2) Redis replicas are able to perform a partial resynchronization with the
#    master if the replication link is lost for a relatively small amount of
#    time. You may want to configure the replication backlog size (see the next
#    sections of this file) with a sensible value depending on your needs.
# 3) Replication is automatic and does not need user intervention. After a
#    network partition replicas automatically try to reconnect to masters
#    and resynchronize with them.
#
# replicaof <masterip> <masterport>
# If the master is password protected (using the "requirepass" configuration
# directive below) it is possible to tell the replica to authenticate before
# starting the replication synchronization process, otherwise the master will
# refuse the replica request.
#
# masterauth <master-password>
#
# However this is not enough if you are using Redis ACLs (for Redis version
# 6 or greater), and the default user is not capable of running the PSYNC
# command and/or other commands needed for replication. In this case it's
# better to configure a special user to use with replication, and specify the
# masteruser configuration as such:
#
# masteruser <username>
#
# When masteruser is specified, the replica will authenticate against its
# master using the new AUTH form: AUTH <username> <password>.
# When a replica loses its connection with the master, or when the replication
# is still in progress, the replica can act in two different ways:
#
# 1) if replica-serve-stale-data is set to 'yes' (the default) the replica will
#    still reply to client requests, possibly with out of date data, or the
#    data set may just be empty if this is the first synchronization.
#
# 2) If replica-serve-stale-data is set to 'no' the replica will reply with
#    an error "SYNC with master in progress" to all commands except:
#    INFO, REPLICAOF, AUTH, PING, SHUTDOWN, REPLCONF, ROLE, CONFIG, SUBSCRIBE,
#    UNSUBSCRIBE, PSUBSCRIBE, PUNSUBSCRIBE, PUBLISH, PUBSUB, COMMAND, POST,
#    HOST and LATENCY.
#
replica-serve-stale-data yes
# You can configure a replica instance to accept writes or not. Writing against
# a replica instance may be useful to store some ephemeral data (because data
# written on a replica will be easily deleted after resync with the master) but
# may also cause problems if clients are writing to it because of a
# misconfiguration.
#
# Since Redis 2.6 by default replicas are read-only.
#
# Note: read only replicas are not designed to be exposed to untrusted clients
# on the internet. It's just a protection layer against misuse of the instance.
# Still a read only replica exports by default all the administrative commands
# such as CONFIG, DEBUG, and so forth. To a limited extent you can improve
# security of read only replicas using 'rename-command' to shadow all the
# administrative / dangerous commands.
replica-read-only yes
# Replication SYNC strategy: disk or socket.
#
# New replicas and reconnecting replicas that are not able to continue the
# replication process just receiving differences, need to do what is called a
# "full synchronization". An RDB file is transmitted from the master to the
# replicas.
#
# The transmission can happen in two different ways:
#
# 1) Disk-backed: The Redis master creates a new process that writes the RDB
#                 file on disk. Later the file is transferred by the parent
#                 process to the replicas incrementally.
# 2) Diskless: The Redis master creates a new process that directly writes the
#              RDB file to replica sockets, without touching the disk at all.
#
# With disk-backed replication, while the RDB file is generated, more replicas
# can be queued and served with the RDB file as soon as the current child
# producing the RDB file finishes its work. With diskless replication instead
# once the transfer starts, new replicas arriving will be queued and a new
# transfer will start when the current one terminates.
#
# When diskless replication is used, the master waits a configurable amount of
# time (in seconds) before starting the transfer in the hope that multiple
# replicas will arrive and the transfer can be parallelized.
#
# With slow disks and fast (large bandwidth) networks, diskless replication
# works better.
repl-diskless-sync no
# When diskless replication is enabled, it is possible to configure the delay
# the server waits in order to spawn the child that transfers the RDB via socket
# to the replicas.
#
# This is important since once the transfer starts, it is not possible to serve
# new replicas arriving, that will be queued for the next RDB transfer, so the
# server waits a delay in order to let more replicas arrive.
#
# The delay is specified in seconds, and by default is 5 seconds. To disable
# it entirely just set it to 0 seconds and the transfer will start ASAP.
repl-diskless-sync-delay 5
# -----------------------------------------------------------------------------
# WARNING: RDB diskless load is experimental. Since in this setup the replica
# does not immediately store an RDB on disk, it may cause data loss during
# failovers. RDB diskless load + Redis modules not handling I/O reads may also
# cause Redis to abort in case of I/O errors during the initial synchronization
# stage with the master. Use only if you know what you are doing.
# -----------------------------------------------------------------------------
#
# Replica can load the RDB it reads from the replication link directly from the
# socket, or store the RDB to a file and read that file after it was completely
# received from the master.
#
# In many cases the disk is slower than the network, and storing and loading
# the RDB file may increase replication time (and even increase the master's
# Copy on Write memory and salve buffers).
# However, parsing the RDB file directly from the socket may mean that we have
# to flush the contents of the current database before the full rdb was
# received. For this reason we have the following options:
#
# "disabled"    - Don't use diskless load (store the rdb file to the disk first)
# "on-empty-db" - Use diskless load only when it is completely safe.
# "swapdb"      - Keep a copy of the current db contents in RAM while parsing
#                 the data directly from the socket. note that this requires
#                 sufficient memory, if you don't have it, you risk an OOM kill.
repl-diskless-load disabled
# Replicas send PINGs to server in a predefined interval. It's possible to
# change this interval with the repl_ping_replica_period option. The default
# value is 10 seconds.
#
# repl-ping-replica-period 10
# The following option sets the replication timeout for:
#
# 1) Bulk transfer I/O during SYNC, from the point of view of replica.
# 2) Master timeout from the point of view of replicas (data, pings).
# 3) Replica timeout from the point of view of masters (REPLCONF ACK pings).
#
# It is important to make sure that this value is greater than the value
# specified for repl-ping-replica-period otherwise a timeout will be detected
# every time there is low traffic between the master and the replica. The default
# value is 60 seconds.
#
# repl-timeout 60
# Disable TCP_NODELAY on the replica socket after SYNC?
#
# If you select "yes" Redis will use a smaller number of TCP packets and
# less bandwidth to send data to replicas. But this can add a delay for
# the data to appear on the replica side, up to 40 milliseconds with
# Linux kernels using a default configuration.
#
# If you select "no" the delay for data to appear on the replica side will
# be reduced but more bandwidth will be used for replication.
#
# By default we optimize for low latency, but in very high traffic conditions
# or when the master and replicas are many hops away, turning this to "yes" may
# be a good idea.
repl-disable-tcp-nodelay no
# Set the replication backlog size. The backlog is a buffer that accumulates
# replica data when replicas are disconnected for some time, so that when a
# replica wants to reconnect again, often a full resync is not needed, but a
# partial resync is enough, just passing the portion of data the replica
# missed while disconnected.
#
# The bigger the replication backlog, the longer the replica can endure the
# disconnect and later be able to perform a partial resynchronization.
#
# The backlog is only allocated if there is at least one replica connected.
#
# repl-backlog-size 1mb
# After a master has no connected replicas for some time, the backlog will be
# freed. The following option configures the amount of seconds that need to
# elapse, starting from the time the last replica disconnected, for the backlog
# buffer to be freed.
#
# Note that replicas never free the backlog for timeout, since they may be
# promoted to masters later, and should be able to correctly "partially
# resynchronize" with other replicas: hence they should always accumulate backlog.
#
# A value of 0 means to never release the backlog.
#
# repl-backlog-ttl 3600
# The replica priority is an integer number published by Redis in the INFO
# output. It is used by Redis Sentinel in order to select a replica to promote
# into a master if the master is no longer working correctly.
#
# A replica with a low priority number is considered better for promotion, so
# for instance if there are three replicas with priority 10, 100, 25 Sentinel
# will pick the one with priority 10, that is the lowest.
#
# However a special priority of 0 marks the replica as not able to perform the
# role of master, so a replica with priority of 0 will never be selected by
# Redis Sentinel for promotion.
#
# By default the priority is 100.
replica-priority 100
# -----------------------------------------------------------------------------
# By default, Redis Sentinel includes all replicas in its reports. A replica
# can be excluded from Redis Sentinel's announcements. An unannounced replica
# will be ignored by the 'sentinel replicas <master>' command and won't be
# exposed to Redis Sentinel's clients.
#
# This option does not change the behavior of replica-priority. Even with
# replica-announced set to 'no', the replica can be promoted to master. To
# prevent this behavior, set replica-priority to 0.
#
# replica-announced yes
# It is possible for a master to stop accepting writes if there are less than
# N replicas connected, having a lag less or equal than M seconds.
#
# The N replicas need to be in "online" state.
#
# The lag in seconds, that must be <= the specified value, is calculated from
# the last ping received from the replica, that is usually sent every second.
#
# This option does not GUARANTEE that N replicas will accept the write, but
# will limit the window of exposure for lost writes in case not enough replicas
# are available, to the specified number of seconds.
#
# For example to require at least 3 replicas with a lag <= 10 seconds use:
#
# min-replicas-to-write 3
# min-replicas-max-lag 10
#
# Setting one or the other to 0 disables the feature.
#
# By default min-replicas-to-write is set to 0 (feature disabled) and
# min-replicas-max-lag is set to 10.
# A Redis master is able to list the address and port of the attached
# replicas in different ways. For example the "INFO replication" section
# offers this information, which is used, among other tools, by
# Redis Sentinel in order to discover replica instances.
# Another place where this info is available is in the output of the
# "ROLE" command of a master.
#
# The listed IP address and port normally reported by a replica is
# obtained in the following way:
#
#   IP: The address is auto detected by checking the peer address
#   of the socket used by the replica to connect with the master.
#
#   Port: The port is communicated by the replica during the replication
#   handshake, and is normally the port that the replica is using to
#   listen for connections.
#
# However when port forwarding or Network Address Translation (NAT) is
# used, the replica may actually be reachable via different IP and port
# pairs. The following two options can be used by a replica in order to
# report to its master a specific set of IP and port, so that both INFO
# and ROLE will report those values.
#
# There is no need to use both the options if you need to override just
# the port or the IP address.
#
# replica-announce-ip 5.5.5.5
# replica-announce-port 1234
############################### KEYS TRACKING #################################
# Redis implements server assisted support for client side caching of values.
# This is implemented using an invalidation table that remembers, using
# a radix key indexed by key name, what clients have which keys. In turn
# this is used in order to send invalidation messages to clients. Please
# check this page to understand more about the feature:
#
#   https://redis.io/topics/client-side-caching
#
# When tracking is enabled for a client, all the read only queries are assumed
# to be cached: this will force Redis to store information in the invalidation
# table. When keys are modified, such information is flushed away, and
# invalidation messages are sent to the clients. However if the workload is
# heavily dominated by reads, Redis could use more and more memory in order
# to track the keys fetched by many clients.
#
# For this reason it is possible to configure a maximum fill value for the
# invalidation table. By default it is set to 1M of keys, and once this limit
# is reached, Redis will start to evict keys in the invalidation table
# even if they were not modified, just to reclaim memory: this will in turn
# force the clients to invalidate the cached values. Basically the table
# maximum size is a trade off between the memory you want to spend server
# side to track information about who cached what, and the ability of clients
# to retain cached objects in memory.
#
# If you set the value to 0, it means there are no limits, and Redis will
# retain as many keys as needed in the invalidation table.
# In the "stats" INFO section, you can find information about the number of
# keys in the invalidation table at every given moment.
#
# Note: when key tracking is used in broadcasting mode, no memory is used
# in the server side so this setting is useless.
#
# tracking-table-max-keys 1000000
################################## SECURITY ###################################
# Warning: since Redis is pretty fast, an outside user can try up to
# 1 million passwords per second against a modern box. This means that you
# should use very strong passwords, otherwise they will be very easy to break.
# Note that because the password is really a shared secret between the client
# and the server, and should not be memorized by any human, the password
# can be easily a long string from /dev/urandom or whatever, so by using a
# long and unguessable password no brute force attack will be possible.
# Redis ACL users are defined in the following format:
#
#   user <username> ... acl rules ...
#
# For example:
#
#   user worker +@list +@connection ~jobs:* on >ffa9203c493aa99
#
# The special username "default" is used for new connections. If this user
# has the "nopass" rule, then new connections will be immediately authenticated
# as the "default" user without the need of any password provided via the
# AUTH command. Otherwise if the "default" user is not flagged with "nopass"
# the connections will start in not authenticated state, and will require
# AUTH (or the HELLO command AUTH option) in order to be authenticated and
# start to work.
#
# The ACL rules that describe what a user can do are the following:
#
#  on           Enable the user: it is possible to authenticate as this user.
#  off          Disable the user: it's no longer possible to authenticate
#               with this user, however the already authenticated connections
#               will still work.
#  skip-sanitize-payload    RESTORE dump-payload sanitation is skipped.
#  sanitize-payload         RESTORE dump-payload is sanitized (default).
#  +<command>   Allow the execution of that command
#  -<command>   Disallow the execution of that command
#  +@<category> Allow the execution of all the commands in such category
#               with valid categories are like @admin, @set, @sortedset, ...
#               and so forth, see the full list in the server.c file where
#               the Redis command table is described and defined.
#               The special category @all means all the commands, but currently
#               present in the server, and that will be loaded in the future
#               via modules.
#  +<command>|subcommand    Allow a specific subcommand of an otherwise
#                           disabled command. Note that this form is not
#                           allowed as negative like -DEBUG|SEGFAULT, but
#                           only additive starting with "+".
#  allcommands  Alias for +@all. Note that it implies the ability to execute
#               all the future commands loaded via the modules system.
#  nocommands   Alias for -@all.
#  ~<pattern>   Add a pattern of keys that can be mentioned as part of
#               commands. For instance ~* allows all the keys. The pattern
#               is a glob-style pattern like the one of KEYS.
#               It is possible to specify multiple patterns.
#  allkeys      Alias for ~*
#  resetkeys    Flush the list of allowed keys patterns.
#  &<pattern>   Add a glob-style pattern of Pub/Sub channels that can be
#               accessed by the user. It is possible to specify multiple channel
#               patterns.
#  allchannels  Alias for &*
#  resetchannels            Flush the list of allowed channel patterns.
#  ><password>  Add this password to the list of valid password for the user.
#               For example >mypass will add "mypass" to the list.
#               This directive clears the "nopass" flag (see later).
#  <<password>  Remove this password from the list of valid passwords.
#  nopass       All the set passwords of the user are removed, and the user
#               is flagged as requiring no password: it means that every
#               password will work against this user. If this directive is
#               used for the default user, every new connection will be
#               immediately authenticated with the default user without
#               any explicit AUTH command required. Note that the "resetpass"
#               directive will clear this condition.
#  resetpass    Flush the list of allowed passwords. Moreover removes the
#               "nopass" status. After "resetpass" the user has no associated
#               passwords and there is no way to authenticate without adding
#               some password (or setting it as "nopass" later).
#  reset        Performs the following actions: resetpass, resetkeys, off,
#               -@all. The user returns to the same state it has immediately
#               after its creation.
#
# ACL rules can be specified in any order: for instance you can start with
# passwords, then flags, or key patterns. However note that the additive
# and subtractive rules will CHANGE MEANING depending on the ordering.
# For instance see the following example:
#
#   user alice on +@all -DEBUG ~* >somepassword
#
# This will allow "alice" to use all the commands with the exception of the
# DEBUG command, since +@all added all the commands to the set of the commands
# alice can use, and later DEBUG was removed. However if we invert the order
# of two ACL rules the result will be different:
#
#   user alice on -DEBUG +@all ~* >somepassword
#
# Now DEBUG was removed when alice had yet no commands in the set of allowed
# commands, later all the commands are added, so the user will be able to
# execute everything.
#
# Basically ACL rules are processed left-to-right.
#
# For more information about ACL configuration please refer to
# the Redis web site at https://redis.io/topics/acl
# ACL LOG
#
# The ACL Log tracks failed commands and authentication events associated
# with ACLs. The ACL Log is useful to troubleshoot failed commands blocked 
# by ACLs. The ACL Log is stored in memory. You can reclaim memory with 
# ACL LOG RESET. Define the maximum entry length of the ACL Log below.
acllog-max-len 128
# Using an external ACL file
#
# Instead of configuring users here in this file, it is possible to use
# a stand-alone file just listing users. The two methods cannot be mixed:
# if you configure users here and at the same time you activate the external
# ACL file, the server will refuse to start.
#
# The format of the external ACL user file is exactly the same as the
# format that is used inside redis.conf to describe users.
#
# aclfile /etc/redis/users.acl
# IMPORTANT NOTE: starting with Redis 6 "requirepass" is just a compatibility
# layer on top of the new ACL system. The option effect will be just setting
# the password for the default user. Clients will still authenticate using
# AUTH <password> as usually, or more explicitly with AUTH default <password>
# if they follow the new protocol: both will work.
#
# The requirepass is not compatable with aclfile option and the ACL LOAD
# command, these will cause requirepass to be ignored.
#
# requirepass foobared
# New users are initialized with restrictive permissions by default, via the
# equivalent of this ACL rule 'off resetkeys -@all'. Starting with Redis 6.2, it
# is possible to manage access to Pub/Sub channels with ACL rules as well. The
# default Pub/Sub channels permission if new users is controlled by the 
# acl-pubsub-default configuration directive, which accepts one of these values:
#
# allchannels: grants access to all Pub/Sub channels
# resetchannels: revokes access to all Pub/Sub channels
#
# To ensure backward compatibility while upgrading Redis 6.0, acl-pubsub-default
# defaults to the 'allchannels' permission.
#
# Future compatibility note: it is very likely that in a future version of Redis
# the directive's default of 'allchannels' will be changed to 'resetchannels' in
# order to provide better out-of-the-box Pub/Sub security. Therefore, it is
# recommended that you explicitly define Pub/Sub permissions for all users
# rather then rely on implicit default values. Once you've set explicit
# Pub/Sub for all existing users, you should uncomment the following line.
#
# acl-pubsub-default resetchannels
# Command renaming (DEPRECATED).
#
# ------------------------------------------------------------------------
# WARNING: avoid using this option if possible. Instead use ACLs to remove
# commands from the default user, and put them only in some admin user you
# create for administrative purposes.
# ------------------------------------------------------------------------
#
# It is possible to change the name of dangerous commands in a shared
# environment. For instance the CONFIG command may be renamed into something
# hard to guess so that it will still be available for internal-use tools
# but not available for general clients.
#
# Example:
#
# rename-command CONFIG b840fc02d524045429941cc15f59e41cb7be6c52
#
# It is also possible to completely kill a command by renaming it into
# an empty string:
#
# rename-command CONFIG ""
#
# Please note that changing the name of commands that are logged into the
# AOF file or transmitted to replicas may cause problems.
################################### CLIENTS ####################################
# Set the max number of connected clients at the same time. By default
# this limit is set to 10000 clients, however if the Redis server is not
# able to configure the process file limit to allow for the specified limit
# the max number of allowed clients is set to the current file limit
# minus 32 (as Redis reserves a few file descriptors for internal uses).
#
# Once the limit is reached Redis will close all the new connections sending
# an error 'max number of clients reached'.
#
# IMPORTANT: When Redis Cluster is used, the max number of connections is also
# shared with the cluster bus: every node in the cluster will use two
# connections, one incoming and another outgoing. It is important to size the
# limit accordingly in case of very large clusters.
#
# maxclients 10000
############################## MEMORY MANAGEMENT ################################
# Set a memory usage limit to the specified amount of bytes.
# When the memory limit is reached Redis will try to remove keys
# according to the eviction policy selected (see maxmemory-policy).
#
# If Redis can't remove keys according to the policy, or if the policy is
# set to 'noeviction', Redis will start to reply with errors to commands
# that would use more memory, like SET, LPUSH, and so on, and will continue
# to reply to read-only commands like GET.
#
# This option is usually useful when using Redis as an LRU or LFU cache, or to
# set a hard memory limit for an instance (using the 'noeviction' policy).
#
# WARNING: If you have replicas attached to an instance with maxmemory on,
# the size of the output buffers needed to feed the replicas are subtracted
# from the used memory count, so that network problems / resyncs will
# not trigger a loop where keys are evicted, and in turn the output
# buffer of replicas is full with DELs of keys evicted triggering the deletion
# of more keys, and so forth until the database is completely emptied.
#
# In short... if you have replicas attached it is suggested that you set a lower
# limit for maxmemory so that there is some free RAM on the system for replica
# output buffers (but this is not needed if the policy is 'noeviction').
#
# maxmemory <bytes>
# MAXMEMORY POLICY: how Redis will select what to remove when maxmemory
# is reached. You can select one from the following behaviors:
#
# volatile-lru -> Evict using approximated LRU, only keys with an expire set.
# allkeys-lru -> Evict any key using approximated LRU.
# volatile-lfu -> Evict using approximated LFU, only keys with an expire set.
# allkeys-lfu -> Evict any key using approximated LFU.
# volatile-random -> Remove a random key having an expire set.
# allkeys-random -> Remove a random key, any key.
# volatile-ttl -> Remove the key with the nearest expire time (minor TTL)
# noeviction -> Don't evict anything, just return an error on write operations.
#
# LRU means Least Recently Used
# LFU means Least Frequently Used
#
# Both LRU, LFU and volatile-ttl are implemented using approximated
# randomized algorithms.
#
# Note: with any of the above policies, when there are no suitable keys for
# eviction, Redis will return an error on write operations that require
# more memory. These are usually commands that create new keys, add data or
# modify existing keys. A few examples are: SET, INCR, HSET, LPUSH, SUNIONSTORE,
# SORT (due to the STORE argument), and EXEC (if the transaction includes any
# command that requires memory).
#
# The default is:
#
# maxmemory-policy noeviction
# LRU, LFU and minimal TTL algorithms are not precise algorithms but approximated
# algorithms (in order to save memory), so you can tune it for speed or
# accuracy. By default Redis will check five keys and pick the one that was
# used least recently, you can change the sample size using the following
# configuration directive.
#
# The default of 5 produces good enough results. 10 Approximates very closely
# true LRU but costs more CPU. 3 is faster but not very accurate.
#
# maxmemory-samples 5
# Eviction processing is designed to function well with the default setting.
# If there is an unusually large amount of write traffic, this value may need to
# be increased.  Decreasing this value may reduce latency at the risk of 
# eviction processing effectiveness
#   0 = minimum latency, 10 = default, 100 = process without regard to latency
#
# maxmemory-eviction-tenacity 10
# Starting from Redis 5, by default a replica will ignore its maxmemory setting
# (unless it is promoted to master after a failover or manually). It means
# that the eviction of keys will be just handled by the master, sending the
# DEL commands to the replica as keys evict in the master side.
#
# This behavior ensures that masters and replicas stay consistent, and is usually
# what you want, however if your replica is writable, or you want the replica
# to have a different memory setting, and you are sure all the writes performed
# to the replica are idempotent, then you may change this default (but be sure
# to understand what you are doing).
#
# Note that since the replica by default does not evict, it may end using more
# memory than the one set via maxmemory (there are certain buffers that may
# be larger on the replica, or data structures may sometimes take more memory
# and so forth). So make sure you monitor your replicas and make sure they
# have enough memory to never hit a real out-of-memory condition before the
# master hits the configured maxmemory setting.
#
# replica-ignore-maxmemory yes
# Redis reclaims expired keys in two ways: upon access when those keys are
# found to be expired, and also in background, in what is called the
# "active expire key". The key space is slowly and interactively scanned
# looking for expired keys to reclaim, so that it is possible to free memory
# of keys that are expired and will never be accessed again in a short time.
#
# The default effort of the expire cycle will try to avoid having more than
# ten percent of expired keys still in memory, and will try to avoid consuming
# more than 25% of total memory and to add latency to the system. However
# it is possible to increase the expire "effort" that is normally set to
# "1", to a greater value, up to the value "10". At its maximum value the
# system will use more CPU, longer cycles (and technically may introduce
# more latency), and will tolerate less already expired keys still present
# in the system. It's a tradeoff between memory, CPU and latency.
#
# active-expire-effort 1
############################# LAZY FREEING ####################################
# Redis has two primitives to delete keys. One is called DEL and is a blocking
# deletion of the object. It means that the server stops processing new commands
# in order to reclaim all the memory associated with an object in a synchronous
# way. If the key deleted is associated with a small object, the time needed
# in order to execute the DEL command is very small and comparable to most other
# O(1) or O(log_N) commands in Redis. However if the key is associated with an
# aggregated value containing millions of elements, the server can block for
# a long time (even seconds) in order to complete the operation.
#
# For the above reasons Redis also offers non blocking deletion primitives
# such as UNLINK (non blocking DEL) and the ASYNC option of FLUSHALL and
# FLUSHDB commands, in order to reclaim memory in background. Those commands
# are executed in constant time. Another thread will incrementally free the
# object in the background as fast as possible.
#
# DEL, UNLINK and ASYNC option of FLUSHALL and FLUSHDB are user-controlled.
# It's up to the design of the application to understand when it is a good
# idea to use one or the other. However the Redis server sometimes has to
# delete keys or flush the whole database as a side effect of other operations.
# Specifically Redis deletes objects independently of a user call in the
# following scenarios:
#
# 1) On eviction, because of the maxmemory and maxmemory policy configurations,
#    in order to make room for new data, without going over the specified
#    memory limit.
# 2) Because of expire: when a key with an associated time to live (see the
#    EXPIRE command) must be deleted from memory.
# 3) Because of a side effect of a command that stores data on a key that may
#    already exist. For example the RENAME command may delete the old key
#    content when it is replaced with another one. Similarly SUNIONSTORE
#    or SORT with STORE option may delete existing keys. The SET command
#    itself removes any old content of the specified key in order to replace
#    it with the specified string.
# 4) During replication, when a replica performs a full resynchronization with
#    its master, the content of the whole database is removed in order to
#    load the RDB file just transferred.
#
# In all the above cases the default is to delete objects in a blocking way,
# like if DEL was called. However you can configure each case specifically
# in order to instead release memory in a non-blocking way like if UNLINK
# was called, using the following configuration directives.
lazyfree-lazy-eviction no
lazyfree-lazy-expire no
lazyfree-lazy-server-del no
replica-lazy-flush no
# It is also possible, for the case when to replace the user code DEL calls
# with UNLINK calls is not easy, to modify the default behavior of the DEL
# command to act exactly like UNLINK, using the following configuration
# directive:
lazyfree-lazy-user-del no
# FLUSHDB, FLUSHALL, and SCRIPT FLUSH support both asynchronous and synchronous
# deletion, which can be controlled by passing the [SYNC|ASYNC] flags into the
# commands. When neither flag is passed, this directive will be used to determine
# if the data should be deleted asynchronously.
lazyfree-lazy-user-flush no
################################ THREADED I/O #################################
# Redis is mostly single threaded, however there are certain threaded
# operations such as UNLINK, slow I/O accesses and other things that are
# performed on side threads.
#
# Now it is also possible to handle Redis clients socket reads and writes
# in different I/O threads. Since especially writing is so slow, normally
# Redis users use pipelining in order to speed up the Redis performances per
# core, and spawn multiple instances in order to scale more. Using I/O
# threads it is possible to easily speedup two times Redis without resorting
# to pipelining nor sharding of the instance.
#
# By default threading is disabled, we suggest enabling it only in machines
# that have at least 4 or more cores, leaving at least one spare core.
# Using more than 8 threads is unlikely to help much. We also recommend using
# threaded I/O only if you actually have performance problems, with Redis
# instances being able to use a quite big percentage of CPU time, otherwise
# there is no point in using this feature.
#
# So for instance if you have a four cores boxes, try to use 2 or 3 I/O
# threads, if you have a 8 cores, try to use 6 threads. In order to
# enable I/O threads use the following configuration directive:
#
# io-threads 4
#
# Setting io-threads to 1 will just use the main thread as usual.
# When I/O threads are enabled, we only use threads for writes, that is
# to thread the write(2) syscall and transfer the client buffers to the
# socket. However it is also possible to enable threading of reads and
# protocol parsing using the following configuration directive, by setting
# it to yes:
#
# io-threads-do-reads no
#
# Usually threading reads doesn't help much.
#
# NOTE 1: This configuration directive cannot be changed at runtime via
# CONFIG SET. Aso this feature currently does not work when SSL is
# enabled.
#
# NOTE 2: If you want to test the Redis speedup using redis-benchmark, make
# sure you also run the benchmark itself in threaded mode, using the
# --threads option to match the number of Redis threads, otherwise you'll not
# be able to notice the improvements.
############################ KERNEL OOM CONTROL ##############################
# On Linux, it is possible to hint the kernel OOM killer on what processes
# should be killed first when out of memory.
#
# Enabling this feature makes Redis actively control the oom_score_adj value
# for all its processes, depending on their role. The default scores will
# attempt to have background child processes killed before all others, and
# replicas killed before masters.
#
# Redis supports three options:
#
# no:       Don't make changes to oom-score-adj (default).
# yes:      Alias to "relative" see below.
# absolute: Values in oom-score-adj-values are written as is to the kernel.
# relative: Values are used relative to the initial value of oom_score_adj when
#           the server starts and are then clamped to a range of -1000 to 1000.
#           Because typically the initial value is 0, they will often match the
#           absolute values.
oom-score-adj no
# When oom-score-adj is used, this directive controls the specific values used
# for master, replica and background child processes. Values range -2000 to
# 2000 (higher means more likely to be killed).
#
# Unprivileged processes (not root, and without CAP_SYS_RESOURCE capabilities)
# can freely increase their value, but not decrease it below its initial
# settings. This means that setting oom-score-adj to "relative" and setting the
# oom-score-adj-values to positive values will always succeed.
oom-score-adj-values 0 200 800
#################### KERNEL transparent hugepage CONTROL ######################
# Usually the kernel Transparent Huge Pages control is set to "madvise" or
# or "never" by default (/sys/kernel/mm/transparent_hugepage/enabled), in which
# case this config has no effect. On systems in which it is set to "always",
# redis will attempt to disable it specifically for the redis process in order
# to avoid latency problems specifically with fork(2) and CoW.
# If for some reason you prefer to keep it enabled, you can set this config to
# "no" and the kernel global to "always".
disable-thp yes
############################## APPEND ONLY MODE ###############################
# By default Redis asynchronously dumps the dataset on disk. This mode is
# good enough in many applications, but an issue with the Redis process or
# a power outage may result into a few minutes of writes lost (depending on
# the configured save points).
#
# The Append Only File is an alternative persistence mode that provides
# much better durability. For instance using the default data fsync policy
# (see later in the config file) Redis can lose just one second of writes in a
# dramatic event like a server power outage, or a single write if something
# wrong with the Redis process itself happens, but the operating system is
# still running correctly.
#
# AOF and RDB persistence can be enabled at the same time without problems.
# If the AOF is enabled on startup Redis will load the AOF, that is the file
# with the better durability guarantees.
#
# Please check https://redis.io/topics/persistence for more information.
appendonly no
# The name of the append only file (default: "appendonly.aof")
appendfilename "appendonly.aof"
# The fsync() call tells the Operating System to actually write data on disk
# instead of waiting for more data in the output buffer. Some OS will really flush
# data on disk, some other OS will just try to do it ASAP.
#
# Redis supports three different modes:
#
# no: don't fsync, just let the OS flush the data when it wants. Faster.
# always: fsync after every write to the append only log. Slow, Safest.
# everysec: fsync only one time every second. Compromise.
#
# The default is "everysec", as that's usually the right compromise between
# speed and data safety. It's up to you to understand if you can relax this to
# "no" that will let the operating system flush the output buffer when
# it wants, for better performances (but if you can live with the idea of
# some data loss consider the default persistence mode that's snapshotting),
# or on the contrary, use "always" that's very slow but a bit safer than
# everysec.
#
# More details please check the following article:
# http://antirez.com/post/redis-persistence-demystified.html
#
# If unsure, use "everysec".
# appendfsync always
appendfsync everysec
# appendfsync no
# When the AOF fsync policy is set to always or everysec, and a background
# saving process (a background save or AOF log background rewriting) is
# performing a lot of I/O against the disk, in some Linux configurations
# Redis may block too long on the fsync() call. Note that there is no fix for
# this currently, as even performing fsync in a different thread will block
# our synchronous write(2) call.
#
# In order to mitigate this problem it's possible to use the following option
# that will prevent fsync() from being called in the main process while a
# BGSAVE or BGREWRITEAOF is in progress.
#
# This means that while another child is saving, the durability of Redis is
# the same as "appendfsync none". In practical terms, this means that it is
# possible to lose up to 30 seconds of log in the worst scenario (with the
# default Linux settings).
#
# If you have latency problems turn this to "yes". Otherwise leave it as
# "no" that is the safest pick from the point of view of durability.
no-appendfsync-on-rewrite no
# Automatic rewrite of the append only file.
# Redis is able to automatically rewrite the log file implicitly calling
# BGREWRITEAOF when the AOF log size grows by the specified percentage.
#
# This is how it works: Redis remembers the size of the AOF file after the
# latest rewrite (if no rewrite has happened since the restart, the size of
# the AOF at startup is used).
#
# This base size is compared to the current size. If the current size is
# bigger than the specified percentage, the rewrite is triggered. Also
# you need to specify a minimal size for the AOF file to be rewritten, this
# is useful to avoid rewriting the AOF file even if the percentage increase
# is reached but it is still pretty small.
#
# Specify a percentage of zero in order to disable the automatic AOF
# rewrite feature.
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb
# An AOF file may be found to be truncated at the end during the Redis
# startup process, when the AOF data gets loaded back into memory.
# This may happen when the system where Redis is running
# crashes, especially when an ext4 filesystem is mounted without the
# data=ordered option (however this can't happen when Redis itself
# crashes or aborts but the operating system still works correctly).
#
# Redis can either exit with an error when this happens, or load as much
# data as possible (the default now) and start if the AOF file is found
# to be truncated at the end. The following option controls this behavior.
#
# If aof-load-truncated is set to yes, a truncated AOF file is loaded and
# the Redis server starts emitting a log to inform the user of the event.
# Otherwise if the option is set to no, the server aborts with an error
# and refuses to start. When the option is set to no, the user requires
# to fix the AOF file using the "redis-check-aof" utility before to restart
# the server.
#
# Note that if the AOF file will be found to be corrupted in the middle
# the server will still exit with an error. This option only applies when
# Redis will try to read more data from the AOF file but not enough bytes
# will be found.
aof-load-truncated yes
# When rewriting the AOF file, Redis is able to use an RDB preamble in the
# AOF file for faster rewrites and recoveries. When this option is turned
# on the rewritten AOF file is composed of two different stanzas:
#
#   [RDB file][AOF tail]
#
# When loading, Redis recognizes that the AOF file starts with the "REDIS"
# string and loads the prefixed RDB file, then continues loading the AOF
# tail.
aof-use-rdb-preamble yes
################################ LUA SCRIPTING  ###############################
# Max execution time of a Lua script in milliseconds.
#
# If the maximum execution time is reached Redis will log that a script is
# still in execution after the maximum allowed time and will start to
# reply to queries with an error.
#
# When a long running script exceeds the maximum execution time only the
# SCRIPT KILL and SHUTDOWN NOSAVE commands are available. The first can be
# used to stop a script that did not yet call any write commands. The second
# is the only way to shut down the server in the case a write command was
# already issued by the script but the user doesn't want to wait for the natural
# termination of the script.
#
# Set it to 0 or a negative value for unlimited execution without warnings.
lua-time-limit 5000
################################ REDIS CLUSTER  ###############################
# Normal Redis instances can't be part of a Redis Cluster; only nodes that are
# started as cluster nodes can. In order to start a Redis instance as a
# cluster node enable the cluster support uncommenting the following:
#
# cluster-enabled yes
# Every cluster node has a cluster configuration file. This file is not
# intended to be edited by hand. It is created and updated by Redis nodes.
# Every Redis Cluster node requires a different cluster configuration file.
# Make sure that instances running in the same system do not have
# overlapping cluster configuration file names.
#
# cluster-config-file nodes-6379.conf
# Cluster node timeout is the amount of milliseconds a node must be unreachable
# for it to be considered in failure state.
# Most other internal time limits are a multiple of the node timeout.
#
# cluster-node-timeout 15000
# A replica of a failing master will avoid to start a failover if its data
# looks too old.
#
# There is no simple way for a replica to actually have an exact measure of
# its "data age", so the following two checks are performed:
#
# 1) If there are multiple replicas able to failover, they exchange messages
#    in order to try to give an advantage to the replica with the best
#    replication offset (more data from the master processed).
#    Replicas will try to get their rank by offset, and apply to the start
#    of the failover a delay proportional to their rank.
#
# 2) Every single replica computes the time of the last interaction with
#    its master. This can be the last ping or command received (if the master
#    is still in the "connected" state), or the time that elapsed since the
#    disconnection with the master (if the replication link is currently down).
#    If the last interaction is too old, the replica will not try to failover
#    at all.
#
# The point "2" can be tuned by user. Specifically a replica will not perform
# the failover if, since the last interaction with the master, the time
# elapsed is greater than:
#
#   (node-timeout * cluster-replica-validity-factor) + repl-ping-replica-period
#
# So for example if node-timeout is 30 seconds, and the cluster-replica-validity-factor
# is 10, and assuming a default repl-ping-replica-period of 10 seconds, the
# replica will not try to failover if it was not able to talk with the master
# for longer than 310 seconds.
#
# A large cluster-replica-validity-factor may allow replicas with too old data to failover
# a master, while a too small value may prevent the cluster from being able to
# elect a replica at all.
#
# For maximum availability, it is possible to set the cluster-replica-validity-factor
# to a value of 0, which means, that replicas will always try to failover the
# master regardless of the last time they interacted with the master.
# (However they'll always try to apply a delay proportional to their
# offset rank).
#
# Zero is the only value able to guarantee that when all the partitions heal
# the cluster will always be able to continue.
#
# cluster-replica-validity-factor 10
# Cluster replicas are able to migrate to orphaned masters, that are masters
# that are left without working replicas. This improves the cluster ability
# to resist to failures as otherwise an orphaned master can't be failed over
# in case of failure if it has no working replicas.
#
# Replicas migrate to orphaned masters only if there are still at least a
# given number of other working replicas for their old master. This number
# is the "migration barrier". A migration barrier of 1 means that a replica
# will migrate only if there is at least 1 other working replica for its master
# and so forth. It usually reflects the number of replicas you want for every
# master in your cluster.
#
# Default is 1 (replicas migrate only if their masters remain with at least
# one replica). To disable migration just set it to a very large value or
# set cluster-allow-replica-migration to 'no'.
# A value of 0 can be set but is useful only for debugging and dangerous
# in production.
#
# cluster-migration-barrier 1
# Turning off this option allows to use less automatic cluster configuration.
# It both disables migration to orphaned masters and migration from masters
# that became empty.
#
# Default is 'yes' (allow automatic migrations).
#
# cluster-allow-replica-migration yes
# By default Redis Cluster nodes stop accepting queries if they detect there
# is at least a hash slot uncovered (no available node is serving it).
# This way if the cluster is partially down (for example a range of hash slots
# are no longer covered) all the cluster becomes, eventually, unavailable.
# It automatically returns available as soon as all the slots are covered again.
#
# However sometimes you want the subset of the cluster which is working,
# to continue to accept queries for the part of the key space that is still
# covered. In order to do so, just set the cluster-require-full-coverage
# option to no.
#
# cluster-require-full-coverage yes
# This option, when set to yes, prevents replicas from trying to failover its
# master during master failures. However the replica can still perform a
# manual failover, if forced to do so.
#
# This is useful in different scenarios, especially in the case of multiple
# data center operations, where we want one side to never be promoted if not
# in the case of a total DC failure.
#
# cluster-replica-no-failover no
# This option, when set to yes, allows nodes to serve read traffic while the
# the cluster is in a down state, as long as it believes it owns the slots. 
#
# This is useful for two cases.  The first case is for when an application 
# doesn't require consistency of data during node failures or network partitions.
# One example of this is a cache, where as long as the node has the data it
# should be able to serve it. 
#
# The second use case is for configurations that don't meet the recommended  
# three shards but want to enable cluster mode and scale later. A 
# master outage in a 1 or 2 shard configuration causes a read/write outage to the
# entire cluster without this option set, with it set there is only a write outage.
# Without a quorum of masters, slot ownership will not change automatically. 
#
# cluster-allow-reads-when-down no
# In order to setup your cluster make sure to read the documentation
# available at https://redis.io web site.
########################## CLUSTER DOCKER/NAT support  ########################
# In certain deployments, Redis Cluster nodes address discovery fails, because
# addresses are NAT-ted or because ports are forwarded (the typical case is
# Docker and other containers).
#
# In order to make Redis Cluster working in such environments, a static
# configuration where each node knows its public address is needed. The
# following four options are used for this scope, and are:
#
# * cluster-announce-ip
# * cluster-announce-port
# * cluster-announce-tls-port
# * cluster-announce-bus-port
#
# Each instructs the node about its address, client ports (for connections
# without and with TLS) and cluster message bus port. The information is then
# published in the header of the bus packets so that other nodes will be able to
# correctly map the address of the node publishing the information.
#
# If cluster-tls is set to yes and cluster-announce-tls-port is omitted or set
# to zero, then cluster-announce-port refers to the TLS port. Note also that
# cluster-announce-tls-port has no effect if cluster-tls is set to no.
#
# If the above options are not used, the normal Redis Cluster auto-detection
# will be used instead.
#
# Note that when remapped, the bus port may not be at the fixed offset of
# clients port + 10000, so you can specify any port and bus-port depending
# on how they get remapped. If the bus-port is not set, a fixed offset of
# 10000 will be used as usual.
#
# Example:
#
# cluster-announce-ip 10.1.1.5
# cluster-announce-tls-port 6379
# cluster-announce-port 0
# cluster-announce-bus-port 6380
################################## SLOW LOG ###################################
# The Redis Slow Log is a system to log queries that exceeded a specified
# execution time. The execution time does not include the I/O operations
# like talking with the client, sending the reply and so forth,
# but just the time needed to actually execute the command (this is the only
# stage of command execution where the thread is blocked and can not serve
# other requests in the meantime).
#
# You can configure the slow log with two parameters: one tells Redis
# what is the execution time, in microseconds, to exceed in order for the
# command to get logged, and the other parameter is the length of the
# slow log. When a new command is logged the oldest one is removed from the
# queue of logged commands.
# The following time is expressed in microseconds, so 1000000 is equivalent
# to one second. Note that a negative number disables the slow log, while
# a value of zero forces the logging of every command.
slowlog-log-slower-than 10000
# There is no limit to this length. Just be aware that it will consume memory.
# You can reclaim memory used by the slow log with SLOWLOG RESET.
slowlog-max-len 128
################################ LATENCY MONITOR ##############################
# The Redis latency monitoring subsystem samples different operations
# at runtime in order to collect data related to possible sources of
# latency of a Redis instance.
#
# Via the LATENCY command this information is available to the user that can
# print graphs and obtain reports.
#
# The system only logs operations that were performed in a time equal or
# greater than the amount of milliseconds specified via the
# latency-monitor-threshold configuration directive. When its value is set
# to zero, the latency monitor is turned off.
#
# By default latency monitoring is disabled since it is mostly not needed
# if you don't have latency issues, and collecting data has a performance
# impact, that while very small, can be measured under big load. Latency
# monitoring can easily be enabled at runtime using the command
# "CONFIG SET latency-monitor-threshold <milliseconds>" if needed.
latency-monitor-threshold 0
############################# EVENT NOTIFICATION ##############################
# Redis can notify Pub/Sub clients about events happening in the key space.
# This feature is documented at https://redis.io/topics/notifications
#
# For instance if keyspace events notification is enabled, and a client
# performs a DEL operation on key "foo" stored in the Database 0, two
# messages will be published via Pub/Sub:
#
# PUBLISH __keyspace@0__:foo del
# PUBLISH __keyevent@0__:del foo
#
# It is possible to select the events that Redis will notify among a set
# of classes. Every class is identified by a single character:
#
#  K     Keyspace events, published with __keyspace@<db>__ prefix.
#  E     Keyevent events, published with __keyevent@<db>__ prefix.
#  g     Generic commands (non-type specific) like DEL, EXPIRE, RENAME, ...
#  $     String commands
#  l     List commands
#  s     Set commands
#  h     Hash commands
#  z     Sorted set commands
#  x     Expired events (events generated every time a key expires)
#  e     Evicted events (events generated when a key is evicted for maxmemory)
#  t     Stream commands
#  d     Module key type events
#  m     Key-miss events (Note: It is not included in the 'A' class)
#  A     Alias for g$lshzxetd, so that the "AKE" string means all the events
#        (Except key-miss events which are excluded from 'A' due to their
#         unique nature).
#
#  The "notify-keyspace-events" takes as argument a string that is composed
#  of zero or multiple characters. The empty string means that notifications
#  are disabled.
#
#  Example: to enable list and generic events, from the point of view of the
#           event name, use:
#
#  notify-keyspace-events Elg
#
#  Example 2: to get the stream of the expired keys subscribing to channel
#             name __keyevent@0__:expired use:
#
#  notify-keyspace-events Ex
#
#  By default all notifications are disabled because most users don't need
#  this feature and the feature has some overhead. Note that if you don't
#  specify at least one of K or E, no events will be delivered.
notify-keyspace-events ""
############################### GOPHER SERVER #################################
# Redis contains an implementation of the Gopher protocol, as specified in
# the RFC 1436 (https://www.ietf.org/rfc/rfc1436.txt).
#
# The Gopher protocol was very popular in the late '90s. It is an alternative
# to the web, and the implementation both server and client side is so simple
# that the Redis server has just 100 lines of code in order to implement this
# support.
#
# What do you do with Gopher nowadays? Well Gopher never *really* died, and
# lately there is a movement in order for the Gopher more hierarchical content
# composed of just plain text documents to be resurrected. Some want a simpler
# internet, others believe that the mainstream internet became too much
# controlled, and it's cool to create an alternative space for people that
# want a bit of fresh air.
#
# Anyway for the 10nth birthday of the Redis, we gave it the Gopher protocol
# as a gift.
#
# --- HOW IT WORKS? ---
#
# The Redis Gopher support uses the inline protocol of Redis, and specifically
# two kind of inline requests that were anyway illegal: an empty request
# or any request that starts with "/" (there are no Redis commands starting
# with such a slash). Normal RESP2/RESP3 requests are completely out of the
# path of the Gopher protocol implementation and are served as usual as well.
#
# If you open a connection to Redis when Gopher is enabled and send it
# a string like "/foo", if there is a key named "/foo" it is served via the
# Gopher protocol.
#
# In order to create a real Gopher "hole" (the name of a Gopher site in Gopher
# talking), you likely need a script like the following:
#
#   https://github.com/antirez/gopher2redis
#
# --- SECURITY WARNING ---
#
# If you plan to put Redis on the internet in a publicly accessible address
# to server Gopher pages MAKE SURE TO SET A PASSWORD to the instance.
# Once a password is set:
#
#   1. The Gopher server (when enabled, not by default) will still serve
#      content via Gopher.
#   2. However other commands cannot be called before the client will
#      authenticate.
#
# So use the 'requirepass' option to protect your instance.
#
# Note that Gopher is not currently supported when 'io-threads-do-reads'
# is enabled.
#
# To enable Gopher support, uncomment the following line and set the option
# from no (the default) to yes.
#
# gopher-enabled no
############################### ADVANCED CONFIG ###############################
# Hashes are encoded using a memory efficient data structure when they have a
# small number of entries, and the biggest entry does not exceed a given
# threshold. These thresholds can be configured using the following directives.
hash-max-ziplist-entries 512
hash-max-ziplist-value 64
# Lists are also encoded in a special way to save a lot of space.
# The number of entries allowed per internal list node can be specified
# as a fixed maximum size or a maximum number of elements.
# For a fixed maximum size, use -5 through -1, meaning:
# -5: max size: 64 Kb  <-- not recommended for normal workloads
# -4: max size: 32 Kb  <-- not recommended
# -3: max size: 16 Kb  <-- probably not recommended
# -2: max size: 8 Kb   <-- good
# -1: max size: 4 Kb   <-- good
# Positive numbers mean store up to _exactly_ that number of elements
# per list node.
# The highest performing option is usually -2 (8 Kb size) or -1 (4 Kb size),
# but if your use case is unique, adjust the settings as necessary.
list-max-ziplist-size -2
# Lists may also be compressed.
# Compress depth is the number of quicklist ziplist nodes from *each* side of
# the list to *exclude* from compression.  The head and tail of the list
# are always uncompressed for fast push/pop operations.  Settings are:
# 0: disable all list compression
# 1: depth 1 means "don't start compressing until after 1 node into the list,
#    going from either the head or tail"
#    So: [head]->node->node->...->node->[tail]
#    [head], [tail] will always be uncompressed; inner nodes will compress.
# 2: [head]->[next]->node->node->...->node->[prev]->[tail]
#    2 here means: don't compress head or head->next or tail->prev or tail,
#    but compress all nodes between them.
# 3: [head]->[next]->[next]->node->node->...->node->[prev]->[prev]->[tail]
# etc.
list-compress-depth 0
# Sets have a special encoding in just one case: when a set is composed
# of just strings that happen to be integers in radix 10 in the range
# of 64 bit signed integers.
# The following configuration setting sets the limit in the size of the
# set in order to use this special memory saving encoding.
set-max-intset-entries 512
# Similarly to hashes and lists, sorted sets are also specially encoded in
# order to save a lot of space. This encoding is only used when the length and
# elements of a sorted set are below the following limits:
zset-max-ziplist-entries 128
zset-max-ziplist-value 64
# HyperLogLog sparse representation bytes limit. The limit includes the
# 16 bytes header. When an HyperLogLog using the sparse representation crosses
# this limit, it is converted into the dense representation.
#
# A value greater than 16000 is totally useless, since at that point the
# dense representation is more memory efficient.
#
# The suggested value is ~ 3000 in order to have the benefits of
# the space efficient encoding without slowing down too much PFADD,
# which is O(N) with the sparse encoding. The value can be raised to
# ~ 10000 when CPU is not a concern, but space is, and the data set is
# composed of many HyperLogLogs with cardinality in the 0 - 15000 range.
hll-sparse-max-bytes 3000
# Streams macro node max size / items. The stream data structure is a radix
# tree of big nodes that encode multiple items inside. Using this configuration
# it is possible to configure how big a single node can be in bytes, and the
# maximum number of items it may contain before switching to a new node when
# appending new stream entries. If any of the following settings are set to
# zero, the limit is ignored, so for instance it is possible to set just a
# max entries limit by setting max-bytes to 0 and max-entries to the desired
# value.
stream-node-max-bytes 4096
stream-node-max-entries 100
# Active rehashing uses 1 millisecond every 100 milliseconds of CPU time in
# order to help rehashing the main Redis hash table (the one mapping top-level
# keys to values). The hash table implementation Redis uses (see dict.c)
# performs a lazy rehashing: the more operation you run into a hash table
# that is rehashing, the more rehashing "steps" are performed, so if the
# server is idle the rehashing is never complete and some more memory is used
# by the hash table.
#
# The default is to use this millisecond 10 times every second in order to
# actively rehash the main dictionaries, freeing memory when possible.
#
# If unsure:
# use "activerehashing no" if you have hard latency requirements and it is
# not a good thing in your environment that Redis can reply from time to time
# to queries with 2 milliseconds delay.
#
# use "activerehashing yes" if you don't have such hard requirements but
# want to free memory asap when possible.
activerehashing yes
# The client output buffer limits can be used to force disconnection of clients
# that are not reading data from the server fast enough for some reason (a
# common reason is that a Pub/Sub client can't consume messages as fast as the
# publisher can produce them).
#
# The limit can be set differently for the three different classes of clients:
#
# normal -> normal clients including MONITOR clients
# replica  -> replica clients
# pubsub -> clients subscribed to at least one pubsub channel or pattern
#
# The syntax of every client-output-buffer-limit directive is the following:
#
# client-output-buffer-limit <class> <hard limit> <soft limit> <soft seconds>
#
# A client is immediately disconnected once the hard limit is reached, or if
# the soft limit is reached and remains reached for the specified number of
# seconds (continuously).
# So for instance if the hard limit is 32 megabytes and the soft limit is
# 16 megabytes / 10 seconds, the client will get disconnected immediately
# if the size of the output buffers reach 32 megabytes, but will also get
# disconnected if the client reaches 16 megabytes and continuously overcomes
# the limit for 10 seconds.
#
# By default normal clients are not limited because they don't receive data
# without asking (in a push way), but just after a request, so only
# asynchronous clients may create a scenario where data is requested faster
# than it can read.
#
# Instead there is a default limit for pubsub and replica clients, since
# subscribers and replicas receive data in a push fashion.
#
# Both the hard or the soft limit can be disabled by setting them to zero.
client-output-buffer-limit normal 0 0 0
client-output-buffer-limit replica 256mb 64mb 60
client-output-buffer-limit pubsub 32mb 8mb 60
# Client query buffers accumulate new commands. They are limited to a fixed
# amount by default in order to avoid that a protocol desynchronization (for
# instance due to a bug in the client) will lead to unbound memory usage in
# the query buffer. However you can configure it here if you have very special
# needs, such us huge multi/exec requests or alike.
#
# client-query-buffer-limit 1gb
# In the Redis protocol, bulk requests, that are, elements representing single
# strings, are normally limited to 512 mb. However you can change this limit
# here, but must be 1mb or greater
#
# proto-max-bulk-len 512mb
# Redis calls an internal function to perform many background tasks, like
# closing connections of clients in timeout, purging expired keys that are
# never requested, and so forth.
#
# Not all tasks are performed with the same frequency, but Redis checks for
# tasks to perform according to the specified "hz" value.
#
# By default "hz" is set to 10. Raising the value will use more CPU when
# Redis is idle, but at the same time will make Redis more responsive when
# there are many keys expiring at the same time, and timeouts may be
# handled with more precision.
#
# The range is between 1 and 500, however a value over 100 is usually not
# a good idea. Most users should use the default of 10 and raise this up to
# 100 only in environments where very low latency is required.
hz 10
# Normally it is useful to have an HZ value which is proportional to the
# number of clients connected. This is useful in order, for instance, to
# avoid too many clients are processed for each background task invocation
# in order to avoid latency spikes.
#
# Since the default HZ value by default is conservatively set to 10, Redis
# offers, and enables by default, the ability to use an adaptive HZ value
# which will temporarily raise when there are many connected clients.
#
# When dynamic HZ is enabled, the actual configured HZ will be used
# as a baseline, but multiples of the configured HZ value will be actually
# used as needed once more clients are connected. In this way an idle
# instance will use very little CPU time while a busy instance will be
# more responsive.
dynamic-hz yes
# When a child rewrites the AOF file, if the following option is enabled
# the file will be fsync-ed every 32 MB of data generated. This is useful
# in order to commit the file to the disk more incrementally and avoid
# big latency spikes.
aof-rewrite-incremental-fsync yes
# When redis saves RDB file, if the following option is enabled
# the file will be fsync-ed every 32 MB of data generated. This is useful
# in order to commit the file to the disk more incrementally and avoid
# big latency spikes.
rdb-save-incremental-fsync yes
# Redis LFU eviction (see maxmemory setting) can be tuned. However it is a good
# idea to start with the default settings and only change them after investigating
# how to improve the performances and how the keys LFU change over time, which
# is possible to inspect via the OBJECT FREQ command.
#
# There are two tunable parameters in the Redis LFU implementation: the
# counter logarithm factor and the counter decay time. It is important to
# understand what the two parameters mean before changing them.
#
# The LFU counter is just 8 bits per key, it's maximum value is 255, so Redis
# uses a probabilistic increment with logarithmic behavior. Given the value
# of the old counter, when a key is accessed, the counter is incremented in
# this way:
#
# 1. A random number R between 0 and 1 is extracted.
# 2. A probability P is calculated as 1/(old_value*lfu_log_factor+1).
# 3. The counter is incremented only if R < P.
#
# The default lfu-log-factor is 10. This is a table of how the frequency
# counter changes with a different number of accesses with different
# logarithmic factors:
#
# +--------+------------+------------+------------+------------+------------+
# | factor | 100 hits   | 1000 hits  | 100K hits  | 1M hits    | 10M hits   |
# +--------+------------+------------+------------+------------+------------+
# | 0      | 104        | 255        | 255        | 255        | 255        |
# +--------+------------+------------+------------+------------+------------+
# | 1      | 18         | 49         | 255        | 255        | 255        |
# +--------+------------+------------+------------+------------+------------+
# | 10     | 10         | 18         | 142        | 255        | 255        |
# +--------+------------+------------+------------+------------+------------+
# | 100    | 8          | 11         | 49         | 143        | 255        |
# +--------+------------+------------+------------+------------+------------+
#
# NOTE: The above table was obtained by running the following commands:
#
#   redis-benchmark -n 1000000 incr foo
#   redis-cli object freq foo
#
# NOTE 2: The counter initial value is 5 in order to give new objects a chance
# to accumulate hits.
#
# The counter decay time is the time, in minutes, that must elapse in order
# for the key counter to be divided by two (or decremented if it has a value
# less <= 10).
#
# The default value for the lfu-decay-time is 1. A special value of 0 means to
# decay the counter every time it happens to be scanned.
#
# lfu-log-factor 10
# lfu-decay-time 1
########################### ACTIVE DEFRAGMENTATION #######################
#
# What is active defragmentation?
# -------------------------------
#
# Active (online) defragmentation allows a Redis server to compact the
# spaces left between small allocations and deallocations of data in memory,
# thus allowing to reclaim back memory.
#
# Fragmentation is a natural process that happens with every allocator (but
# less so with Jemalloc, fortunately) and certain workloads. Normally a server
# restart is needed in order to lower the fragmentation, or at least to flush
# away all the data and create it again. However thanks to this feature
# implemented by Oran Agra for Redis 4.0 this process can happen at runtime
# in a "hot" way, while the server is running.
#
# Basically when the fragmentation is over a certain level (see the
# configuration options below) Redis will start to create new copies of the
# values in contiguous memory regions by exploiting certain specific Jemalloc
# features (in order to understand if an allocation is causing fragmentation
# and to allocate it in a better place), and at the same time, will release the
# old copies of the data. This process, repeated incrementally for all the keys
# will cause the fragmentation to drop back to normal values.
#
# Important things to understand:
#
# 1. This feature is disabled by default, and only works if you compiled Redis
#    to use the copy of Jemalloc we ship with the source code of Redis.
#    This is the default with Linux builds.
#
# 2. You never need to enable this feature if you don't have fragmentation
#    issues.
#
# 3. Once you experience fragmentation, you can enable this feature when
#    needed with the command "CONFIG SET activedefrag yes".
#
# The configuration parameters are able to fine tune the behavior of the
# defragmentation process. If you are not sure about what they mean it is
# a good idea to leave the defaults untouched.
# Enabled active defragmentation
# activedefrag no
# Minimum amount of fragmentation waste to start active defrag
# active-defrag-ignore-bytes 100mb
# Minimum percentage of fragmentation to start active defrag
# active-defrag-threshold-lower 10
# Maximum percentage of fragmentation at which we use maximum effort
# active-defrag-threshold-upper 100
# Minimal effort for defrag in CPU percentage, to be used when the lower
# threshold is reached
# active-defrag-cycle-min 1
# Maximal effort for defrag in CPU percentage, to be used when the upper
# threshold is reached
# active-defrag-cycle-max 25
# Maximum number of set/hash/zset/list fields that will be processed from
# the main dictionary scan
# active-defrag-max-scan-fields 1000
# Jemalloc background thread for purging will be enabled by default
jemalloc-bg-thread yes
# It is possible to pin different threads and processes of Redis to specific
# CPUs in your system, in order to maximize the performances of the server.
# This is useful both in order to pin different Redis threads in different
# CPUs, but also in order to make sure that multiple Redis instances running
# in the same host will be pinned to different CPUs.
#
# Normally you can do this using the "taskset" command, however it is also
# possible to this via Redis configuration directly, both in Linux and FreeBSD.
#
# You can pin the server/IO threads, bio threads, aof rewrite child process, and
# the bgsave child process. The syntax to specify the cpu list is the same as
# the taskset command:
#
# Set redis server/io threads to cpu affinity 0,2,4,6:
# server_cpulist 0-7:2
#
# Set bio threads to cpu affinity 1,3:
# bio_cpulist 1,3
#
# Set aof rewrite child process to cpu affinity 8,9,10,11:
# aof_rewrite_cpulist 8-11
#
# Set bgsave child process to cpu affinity 1,10,11
# bgsave_cpulist 1,10-11
# In some cases redis will emit warnings and even refuse to start if it detects
# that the system is in bad state, it is possible to suppress these warnings
# by setting the following config which takes a space delimited list of warnings
# to suppress
#
# ignore-warnings ARM64-COW-BUG

附

这里说一个冷知识，大家估计都知道Redis的端口是6379，为什么是6379，就让作者来解释一下吧。

Appendix: how to remember the Redis port number

Today on Twitter I saw a tweet related to the ability to remember the Redis port number. There is a trick, the Redis port number, 6379, is MERZ at the phone keyboard.
Is it a coincidence that it sounds not random enough? Actually not ;) I selected 6379 because of MERZ, and not the other way around.
Everything started with Alessia Merz, an Italian Showgirl (make sure to check some (not safe for work) photo as well).
I and my friends are used to create our own slang, that is evolving since… 20 or 25 years. Well one adjective that we use consistently since 10 years is “merz”, but the meaning of the word changed so much in the course of the time.

原文地址：http://oldblog.antirez.com/post/redis-as-LRU-cache.html