flink中zk引起的重启怎么解决
这篇文章主要介绍"flink中zk引起的重启怎么解决"，在日常操作中，相信很多人在flink中zk引起的重启怎么解决问题上存在疑惑，小编查阅了各式资料，整理出简单好用的操作方法，希望对大家解答"flink中zk引起的重启怎么解决"的疑惑有所帮助！接下来，请跟着小编一起来学习吧！
背景
最近用flink on k8s跑程序的过程中，发现某个时刻经常导致程序重启，定时任务每天加载一次缓存，该缓存有大量数据，加载时长需要60-90s左右。这个定时任务经常会导致k8s重启程序，使其极不稳定，于是各种调优。
内存相关
怀疑可能是算子的sender和receiver之间因为加载缓存导致某种通信不可达，默认的心跳时间是50s，于是修改参数：heartbeat.timeout: 180000，heartbeat.interval: 20000。
jobmanager和taskmanager是用akka通信，修改参数akka.ask.timeout: 240s。
这些操作之后，偶尔还是会在加载缓存的时候发现异常，日志截取如下
2020-10-16 17:05:05,939 WARN org.apache.flink.shaded.zookeeper.org.apache.zookeeper.ClientCnxn - Client session timed out, have not heard from server in 29068ms for sessionid 0x30135fa8005449f2020-10-16 17:05:05,948 INFO org.apache.flink.shaded.zookeeper.org.apache.zookeeper.ClientCnxn - Client session timed out, have not heard from server in 29068ms for sessionid 0x30135fa8005449f, closing socket connection and attempting reconnect2020-10-16 17:05:07,609 INFO org.apache.flink.shaded.curator.org.apache.curator.framework.state.ConnectionStateManager - State change: SUSPENDED2020-10-16 17:05:07,611 WARN org.apache.flink.runtime.leaderretrieval.ZooKeeperLeaderRetrievalService - Connection to ZooKeeper suspended. Can no longer retrieve the leader from ZooKeeper.2020-10-16 17:05:07,612 INFO org.apache.flink.runtime.taskexecutor.TaskExecutor - JobManager for job 1bb3b7bdcfbc39cf760064ed9736ea80 with leader id bed26e07640e5e79197e468c85354534 lost leadership.2020-10-16 17:05:07,613 WARN org.apache.flink.runtime.leaderretrieval.ZooKeeperLeaderRetrievalService - Connection to ZooKeeper suspended. Can no longer retrieve the leader from ZooKeeper.2020-10-16 17:05:07,614 INFO org.apache.flink.runtime.taskexecutor.TaskExecutor - Close JobManager connection for job 1bb3b7bdcfbc39cf760064ed9736ea80.2020-10-16 17:05:07,615 INFO org.apache.flink.runtime.taskmanager.Task - Attempting to fail task externally Source: Custom Source -> Flat Map -> Timestamps/Watermarks (15/15) (052a84a37a0647ab485baa54f149b762).2020-10-16 17:05:07,615 INFO org.apache.flink.runtime.taskmanager.Task - Source: Custom Source -> Flat Map -> Timestamps/Watermarks (15/15) (052a84a37a0647ab485baa54f149b762) switched from RUNNING to FAILED.org.apache.flink.util.FlinkException: JobManager responsible for 1bb3b7bdcfbc39cf760064ed9736ea80 lost the leadership.at org.apache.flink.runtime.taskexecutor.TaskExecutor.closeJobManagerConnection(TaskExecutor.java:1274)at org.apache.flink.runtime.taskexecutor.TaskExecutor.access$1200(TaskExecutor.java:155)at org.apache.flink.runtime.taskexecutor.TaskExecutor$JobLeaderListenerImpl.lambda$jobManagerLostLeadership$1(TaskExecutor.java:1698)at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleRunAsync(AkkaRpcActor.java:402)at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleRpcMessage(AkkaRpcActor.java:195)at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleMessage(AkkaRpcActor.java:152)at akka.japi.pf.UnitCaseStatement.apply(CaseStatements.scala:26)at akka.japi.pf.UnitCaseStatement.apply(CaseStatements.scala:21)at scala.PartialFunction$class.applyOrElse(PartialFunction.scala:123)at akka.japi.pf.UnitCaseStatement.applyOrElse(CaseStatements.scala:21)at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:170)at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:171)at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:171)at akka.actor.Actor$class.aroundReceive(Actor.scala:517)at akka.actor.AbstractActor.aroundReceive(AbstractActor.scala:225)at akka.actor.ActorCell.receiveMessage(ActorCell.scala:592)at akka.actor.ActorCell.invoke(ActorCell.scala:561)at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:258)at akka.dispatch.Mailbox.run(Mailbox.scala:225)at akka.dispatch.Mailbox.exec(Mailbox.scala:235)at akka.dispatch.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)at akka.dispatch.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)at akka.dispatch.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)at akka.dispatch.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)Caused by: java.lang.Exception: Job leader for job id 1bb3b7bdcfbc39cf760064ed9736ea80 lost leadership.... 22 more
再经过调查发现，这个跟zk有关系，zk在切换leader或者遇到网络波动之类的，会触发SUSPENDED状态，这个状态，会导致lost the leadership错误，而遇到这个错误，k8s直接就重启程序。其实访问zk还是正常的。 再经过一系列调查，这种问题别人早就遇到，还改了代码，就是flink官方没合并代码。调查的过程不表，有用的链接如下
https://www.cnblogs.com/029zz010buct/p/10946244.html
这个有用的是升级curator包， flink用的是2.12.0，暂时没去操作，里面提到的SessionConnectionStateErrorPolicy是在4.x版本的，应该还是要去编译部分代码。
https://github.com/apache/flink/pull/9066 https://issues.apache.org/jira/browse/FLINK-10052
这个是其他人的解决方案，本人用的也是这个方法。 不把SUSPENDED状态认为是lost leadership，修改LeaderLatch的handleStateChange方法
case RECONNECTED: { try { if (!hasLeadership.get()) { reset(); } } catch ( Exception e ) { ThreadUtils.checkInterrupted(e); log.error("Could not reset leader latch", e); setLeadership(false); } break; } case LOST: { setLeadership(false); break; }编译flink-shaded-hadoop-2-uber
找到这段代码之后，自然是找到了flink-shaded-hadoop-2-uber-xxx.jar这个包，在flink1.10的版本，还支持hadoop的这个包，在1.11之后已经不再主动支持，需要的要自己去下载，因为这个包在打镜像时会特意加上去，所以目标锁定这个包，重新编译。简单说下编译过程
https://github.com/apache/curator/tree/apache-curator-2.12.0 下载这个版本的源码，修改curator-recipes下的src/main/java/org/apache/curator/framework/recipes/leader/LeaderLatch.java，修改内容如上所示，打的包是2.12.0。
https://github.com/apache/flink-shaded/tree/release-10.0 下载flink-shaded 1.10版本的源码，修改flink-shaded-hadoop-2-parent的pom文件，增加exclusion，去掉curator-recipes的依赖，增加自己编译的curator-recipes。观察到不去掉依赖，默认是2.7.1版本，应该是这块代码好多年没动过，版本一直停留在2.7.1。
org.apache.hadoop hadoop-common ${hadoop.version} ...省略若干exclusion org.apache.curator curator-recipes org.apache.curator curator-recipes 2.12.0
因为我们用的是2.8.3-10.0版本的，源码是2.4.1的，修改成
2.8.3 看根目录的readme.md，在flink-shaded-release-10.0/flink-shaded-hadoop-2-parent目录运行mvn package -Dshade-sources打包，打包完成之后，用工具反编译观察一下，SUSPENDED的代码确实去掉了，重新打镜像，跑程序。
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