Java查询时间段(startTime
331
2022-08-03
elasticsearch集群cluster discovery可配式模块示例分析
目录前言Discovery模块的概述cluster节点探测MasterFaultDetection的启动代码master连接失败的逻辑MasterPing的关键代码
前言
elasticsearch cluster实现了自己发现机制zen。Discovery功能主要包括以下几部分内容:master选举,master错误探测,集群中其它节点探测,单播多播ping。本篇会首先概述以下Discovery这一部分的功能,然后介绍节点检测。其它内容会在接下来介绍。
Discovery模块的概述
discovery是可配式模块,官方支持亚马逊的Azure discovery,Google Compute Engine,EC2 Discovery三种发现机制,根据插件规则完全可以自己实现其它的发现机制。整个模块通过实现guice的DiscoveryModule对外提供模块的注册和启动, 默认使用zen discovery。发现模块对外接口为DiscoveryService,它的方法如下所示:
它本质上是discovery的一个代理,所有的功能最终都是由所绑定的discovery所实现的。节点启动时通过DiscoveryModule获取DiscoveryService,然后启动DiscoveryService,DiscoveryService启动绑定的Discovery,整个功能模块就完成了加载和启动。这也是elasticsearch所有模块的实现方式,通过module对外提供绑定和获取,通过service接口对外提供模块的功能,在后面的分析中会经常遇到。
cluster节点探测
接下来分析cluster的一个重要功能就是节点探测。cluster中不能没有master节点,因此集群中所有节点都要周期探测master节点,一旦无法检测到,将会进行master选举。同时作为master,对于节点变动也要时刻关注,因此它需要周期性探测集群中所有节点,确保及时剔除已经宕机的节点。这种相互间的心跳检测就是cluster的faultdetection。下图是faultdetection的继承关系:
有两种实现方式,分别是master探测集群中其它节点和其它节点对master节点的探测。
FaultDetection只要一个抽象方法handleTransportDisconnect,该方法在内部类FDConnectionListener中被调用。在elasticsearch中大量使用了listener的异步方式,异步可以极大提升系统性能。它的代码如下所示:
private class FDConnectionListener implements TransportConnectionListener {
@Override
public void onNodeConnected(DiscoveryNode node) {
}
@Override
public void onNodeDisconnected(DiscoveryNode node) {
handleTransportDisconnect(node);
}
}
faultdetection启动时会注册相应的FDConnetionListener,当探测到节点丢失,会通过onNodeDisconnected方法回调对于的handleTransportDisconnect进行处理。
MasterFaultDetection的启动代码
privatevoidinnerStart(finalDiscoveryNode masterNode) {
this.masterNode = masterNode;
this.retryCount = 0;
this.notifiedMasterFailure.set(false);
// 尝试连接master节点
try {
transportService.connectToNode(masterNode);
} catch (final Exception e) {
// 连接失败通知masterNode失败
notifyMasterFailure(masterNode, "failed to perform initial connect [" + e.getMessage() + "]");
return;
}
//关闭之前的masterping,重启新的masterping
if (masterPinger != null) {
masterPinger.stop();
}
this.masterPinger = new MasterPinger();
// 周期之后启动masterPing,这里并没有周期启动masterPing,只是设定了延迟时间。
threadPool.schedule(pingInterval, ThreadPool.Names.SAME, masterPinger);
}
代码有有详细注释,就不再过多解释。
master连接失败的逻辑
代码如下:
private void notifyMasterFailure(final DiscoveryNode masterNode, final String reason) {
if (notifiedMasterFailure.compareAndSet(false, true)) {
threadPool.generic().execute(new Runnable() {
@Override
public void run() {
//通知所有listener master丢失
for (Listener listener : listeners) {
listener.onMasterFailure(masterNode, reason);
}
}
});
stop("master failure, " + reason);
}
}
在ZenDiscovery中实现了listener.onMasterFailure接口。会进行master丢失的相关处理,在后面再分析。
MasterPing的关键代码
private class MasterPinger implements Runnable {
private volatile boolean running = true;
public void stop() {
this.running = false;
}
@Override
public void run() {
if (!running) {
// return and don't spawn...
return;
}
final DiscoveryNode masterToPing = masterNode;
final MasterPingRequest request = new MasterPingRequest(clusterService.localNode().id(), masterToPing.id(), clusterName);
final TransportRequestOptions options = options().withType(TransportRequestOptions.Type.PING).withTimeout(pingRetryTimeout);
transportService.sendRequest(masterToPing, MASTER_PING_ACTION_NAME, request, options, new BaseTransportResponseHandler
@Override
public MasterPingResponseResponse newInstance() {
return new MasterPingResponseResponse();
}
@Override
public void handleResponse(MasterPingResponseResponse response) {
if (!running) {
return;
}
// reset the counter, we got a good result
MasterFaultDetection.this.retryCount = 0;
// check if the master node did not get switched on us..., if it did, we simply return with no reschedule
if (masterToPing.equals(MasterFaultDetection.this.masterNode())) {
// 启动新的ping周期
threadPool.schedule(pingInterval, ThreadPool.Names.SAME, MasterPinger.this);
}
}
@Override
public void handleException(TransportException exp) {
if (!running) {
return;
}
synchronized (masterNodeMutex) {
// check if the master node did not get switched on us...
if (masterToPing.equals(MasterFaultDetection.this.masterNode())) {
if (exp instanceof ConnectTransportException || exp.getCause() instanceof ConnectTransportException) {
handleTransportDisconnect(masterToPing);
return;
} else if (exp.getCause() instanceof NoLongerMasterException) {
logger.debug("[master] pinging a master {} that is no longer a master", masterNode);
notifyMasterFailure(masterToPing, "no longer master");
return;
} else if (exp.getCause() instanceof NotMasterException) {
logger.debug("[master] pinging a master {} that is not the master", masterNode);
notifyMasterFailure(masterToPing, "not master");
return;
} else if (exp.getCause() instanceof NodeDoesNotExistOnMasterException) {
logger.debug("[master] pinging a master {} but we do not exists on it, act as if its master failure", masterNode);
notifyMasterFailure(masterToPing, "do not exists on master, act as master failure");
return;
}
int retryCount = ++MasterFaultDetection.this.retryCount;
logger.trace("[master] failed to ping [{}], retry [{}] out of [{}]", exp, masterNode, retryCount, pingRetryCount);
if (retryCount >= pingRetryCount) {
logger.debug("[master] failed to ping [{}], tried [{}] times, each with maximum [{}] timeout", masterNode, pingRetryCount, pingRetryTimeout);
// not good, failure
notifyMasterFailure(masterToPing, "failed to ping, tried [" + pingRetryCount + "] times, each with maximum [" + pingRetryTimeout + "] timeout");
} else {
// resend the request, not reschedule, rely on send timeout
transportService.sendRequest(masterToPing, MASTER_PING_ACTION_NAME, request, options, this);
}
}
}
}
);
}
}
MasterPing是一个线程,在innerStart的方法中没有设定周期启动masterping,但是masterping需要周期进行,这个秘密就在run 方法中,如果ping成功就会重启一个新的ping。这样既保证了ping线程的唯一性同时也保证了ping的顺http://序和间隔。
ping的方式跟之前一样是也是通过transport发送一个masterpingrequest,进行一个连接。节点收到该请求后,如果已不再是master会抛出NotMasterException,状态更新出差会抛出其它异常,异常会通过。否则会正常响应notifyMasterFailure方法处理跟启动逻辑一样。
对于网络问题导致的无响应情况,会调用handleTransportDisconnect(masterToPing)方法处理。masterfaultDetection对该方法的实现如下:
protected void handleTransportDisconnect(DiscoveryNode node) {
//这里需要同步
synchronized (masterNodeMutex) {
//master 已经换成其它节点,就没必要再连接
if (!node.equals(this.masterNode)) {
return;
}
if (connectOnNetworkDisconnect) {
try {
//尝试再次连接
transportService.connectToNode(node);
// if all is well, make sure we restart the pinger
if (masterPinger != null) {
masterPinger.stop();
}
//连接成功启动新的masterping
this.masterPinger = new MasterPinger();
// we use schedule with a 0 time value to run the pinger on the pool as it will run on later
threadPool.schedule(TimeValue.timeValueMillis(0), ThreadPool.Names.SAME, masterPinger);
} catch (Exception e) {
//连接出现异常,启动master节点丢失通知
logger.trace("[master] [{}] transport disconnected (with verified connect)", masterNode);
notifyMasterFailure(masterNode, "transport disconnected (with verified connect)");
}
} else {
//不需要重连,通知master丢失。
logger.trace("[master] [{}] transport disconnected", node);
notifyMasterFailure(node, "transport disconnected");
}
}
}
这就是masterfaultDetection的整个流程:启动中如果master丢失则通知节点丢失,否则在一定延迟(3s)后启动masterping,masterping线程尝试连接master节点,如果master节点网络失联,尝试再次连接。master节点收到masterpingrequest后首先看一下自己还是不是master,如果不是则抛出异常,否则正常回应。节点如果收到响应是异常则启动master丢失通知,否则此次ping结束。在一定延迟后启动新的masterping线程。
版权声明:本文内容由网络用户投稿,版权归原作者所有,本站不拥有其著作权,亦不承担相应法律责任。如果您发现本站中有涉嫌抄袭或描述失实的内容,请联系我们jiasou666@gmail.com 处理,核实后本网站将在24小时内删除侵权内容。
发表评论
暂时没有评论,来抢沙发吧~