upstream 负载均衡算法

round-robin
keepalive
hash
ip_hash
一致性hash算法
least_conn

upstream 模块间的顺序 功能的正常运行

  1. ngx_module_t *ngx_modules[] = {
  2. … …
  3.   &ngx_http_upstream_hash_module,
  4.   &ngx_http_upstream_ip_hash_module,
  5.   &ngx_http_upstream_least_conn_module,
  6.   &ngx_http_upstream_random_module,
  7.   &ngx_http_upstream_keepalive_module,
  8.   &ngx_http_upstream_zone_module,
  9. }

Embedded Variables 内置变量

官方文档 http://nginx.org/en/docs/http/ngx_http_upstream_module.html#var_upstream_addr

The ngxhttp_upstream_module module supports the following embedded variables:
$upstream_addr
keeps the IP address and port, or the path to the UNIX-domain socket of the upstream server. If several servers were contacted during request processing, their addresses are separated by commas, e.g. “192.168.1.1:80, 192.168.1.2:80, unix:/tmp/sock”. If an internal redirect from one server group to another happens, initiated by “X-Accel-Redirect” or error_page, then the server addresses from different groups are separated by colons, e.g. “192.168.1.1:80, 192.168.1.2:80, unix:/tmp/sock : 192.168.10.1:80, 192.168.10.2:80”. If a server cannot be selected, the variable keeps the name of the server group.
$upstream_bytes_received
number of bytes received from an upstream server (1.11.4). Values from several connections are separated by commas and colons like addresses in the $upstream_addr variable.
$upstream_bytes_sent
number of bytes sent to an upstream server (1.15.8). Values from several connections are separated by commas and colons like addresses in the $upstream_addr variable.
$upstream_cache_status
keeps the status of accessing a response cache (0.8.3). The status can be either “MISS”, “BYPASS”, “EXPIRED”, “STALE”, “UPDATING”, “REVALIDATED”, or “HIT”.
$upstream_connect_time
keeps time spent on establishing a connection with the upstream server (1.9.1); the time is kept in seconds with millisecond resolution. In case of SSL, includes time spent on handshake. Times of several connections are separated by commas and colons like addresses in the $upstream_addr variable.
$upstream_cookie_name
cookie with the specified name sent by the upstream server in the “Set-Cookie” response header field (1.7.1). Only the cookies from the response of the last server are saved.
$upstream_header_time
keeps time spent on receiving the response header from the upstream server (1.7.10); the time is kept in seconds with millisecond resolution. Times of several responses are separated by commas and colons like addresses in the $upstream_addr variable.
$upstream_http_name
keep server response header fields. For example, the “Server” response header field is available through the $upstream_http_server variable. The rules of converting header field names to variable names are the same as for the variables that start with the “$http” prefix. Only the header fields from the response of the last server are saved.
$upstream_queue_time
keeps time the request spent in the upstream queue (1.13.9); the time is kept in seconds with millisecond resolution. Times of several responses are separated by commas and colons like addresses in the $upstream_addr variable.
$upstream_response_length
keeps the length of the response obtained from the upstream server (0.7.27); the length is kept in bytes. Lengths of several responses are separated by commas and colons like addresses in the $upstream_addr variable.
$upstream_response_time
keeps time spent on receiving the response from the upstream server; the time is kept in seconds with millisecond resolution. Times of several responses are separated by commas and colons like addresses in the $upstream_addr variable.
$upstream_status
keeps status code of the response obtained from the upstream server. Status codes of several responses are separated by commas and colons like addresses in the $upstream_addr variable. If a server cannot be selected, the variable keeps the 502 (Bad Gateway) status code.
$upstream_trailer_name
keeps fields from the end of the response obtained from the upstream server (1.13.10).