一、leaf初始化
- 生成workerID 利用zk顺序节点,不同集群节点的workerID不同
创建临时节点 创建零时节点,并且在节点写入ip、端口、本机时间,
{"ip":"10.194.86.217","port":"8080","timestamp":1644827355855}
心跳检查 为了防止leaf掉线可能导致垃圾数据,对齐心跳检查活跃状态,通过心跳检查节点时钟回拨
时钟回拨 通过心跳检查时钟回拨
public boolean init() {
try {
CuratorFramework curator = createWithOptions(connectionString, new RetryUntilElapsed(1000, 4), 10000, 6000);
curator.start();
Stat stat = curator.checkExists().forPath(PATH_FOREVER);
if (stat == null) {
//不存在根节点,机器第一次启动,创建/snowflake/ip:port-000000000,并上传数据
zk_AddressNode = createNode(curator);
//worker id 默认是0
updateLocalWorkerID(workerID);
//定时上报本机时间给forever节点
ScheduledUploadData(curator, zk_AddressNode);
return true;
} else {
Map<String, Integer> nodeMap = Maps.newHashMap();//ip:port->00001
Map<String, String> realNode = Maps.newHashMap();//ip:port->(ipport-000001)
//存在根节点,先检查是否有属于自己的根节点
List<String> keys = curator.getChildren().forPath(PATH_FOREVER);
for (String key : keys) {
String[] nodeKey = key.split("-");
realNode.put(nodeKey[0], key);
nodeMap.put(nodeKey[0], Integer.parseInt(nodeKey[1]));
}
Integer workerid = nodeMap.get(listenAddress);
if (workerid != null) {
//有自己的节点,zk_AddressNode=ip:port
zk_AddressNode = PATH_FOREVER + "/" + realNode.get(listenAddress);
workerID = workerid;//启动worder时使用会使用
if (!checkInitTimeStamp(curator, zk_AddressNode)) {
throw new CheckLastTimeException("init timestamp check error,forever node timestamp gt this node time");
}
//准备创建临时节点
doService(curator);
updateLocalWorkerID(workerID);
LOGGER.info("[Old NODE]find forever node have this endpoint ip-{} port-{} workid-{} childnode and start SUCCESS", ip, port, workerID);
} else {
//表示新启动的节点,创建持久节点 ,不用check时间
String newNode = createNode(curator);
zk_AddressNode = newNode;
String[] nodeKey = newNode.split("-");
workerID = Integer.parseInt(nodeKey[1]);
doService(curator);
updateLocalWorkerID(workerID);
LOGGER.info("[New NODE]can not find node on forever node that endpoint ip-{} port-{} workid-{},create own node on forever node and start SUCCESS ", ip, port, workerID);
}
}
} catch (Exception e) {
LOGGER.error("Start node ERROR {}", e);
try {
Properties properties = new Properties();
properties.load(new FileInputStream(new File(PROP_PATH.replace("{port}", port + ""))));
workerID = Integer.valueOf(properties.getProperty("workerID"));
LOGGER.warn("START FAILED ,use local node file properties workerID-{}", workerID);
} catch (Exception e1) {
LOGGER.error("Read file error ", e1);
return false;
}
}
return true;
}
二、leaf获取snowflakeid
这段代码就是snowflake的核心算法,需要了解其算法看snowflake算法. ```plsql public synchronized Result get(String key) {
//获取时间戳
long timestamp = timeGen();
//如果当前时间戳小于最后一次生成id时间戳
if (timestamp < lastTimestamp) {
long offset = lastTimestamp - timestamp;
if (offset <= 5) {
try {
//线程暂停
wait(offset << 1);
timestamp = timeGen();
//再次获取当前时间,如果还小于最后时间抛出异常
if (timestamp < lastTimestamp) {
return new Result(-1, Status.EXCEPTION);
}
} catch (InterruptedException e) {
LOGGER.error("wait interrupted");
return new Result(-2, Status.EXCEPTION);
}
} else {
return new Result(-3, Status.EXCEPTION);
}
}
//如果当前时间等于最后生成key时间戳
if (lastTimestamp == timestamp) {
//序列号自动加一,目的防止生成key重复
sequence = (sequence + 1) & sequenceMask;
//?这段代码什么目的?谁知道留言!
if (sequence == 0) {
//seq 为0的时候表示是下一毫秒时间开始对seq做随机
sequence = RANDOM.nextInt(100);
timestamp = tilNextMillis(lastTimestamp);
}
} else {
//如果是新的ms开始
sequence = RANDOM.nextInt(100);
}
lastTimestamp = timestamp;
/*
* 1、(timestamp - twepoch) 这步很重要,如果不做这步会从1970-01-01 08:00:00开始计时,预计2042年结束计时,减去START_TIME,可以从START_TIME时间点计时,让snowflake寿命更长!!!
* 2、timestampLeftShift为啥是22? SnowFlake算法是计算用69年,这个时间戳移位22不超过long.max,故最大只能用22,防止越界.
* “1970-01-01 08:00:00的时间戳是0,加上69年后,时间戳是2177452800000,在移位22,就到long.max边界了”
* 3、 (workerId << workerIdShift) 用途是按照数据中心,集群机器id求或,目的让数据key按照数据中心和集群规则分布
* 4、sequence, 用途是按照随机数求或,目的让可以最后按照最后的key规则生成
*/
long id = ((timestamp - twepoch) << timestampLeftShift) | (workerId << workerIdShift) | sequence;
return new Result(id, Status.SUCCESS);