关于Flink外部化检查点的两个问题

Question

我有两个关于Flink外部化检查站的问题

（Q1）我可以在flink-conf.yaml中设置“state.checkpoints.dir”，以使外部化的检查点正常工作，但当我从IDE运行flink时，如何实现同样的效果呢？我尝试了中提到的全局配置方法(http://apache-flink-user-mailing-list-archive.2336050.n4.nabble.com/state-checkpoints-dir-td17921.html)但运气不好。我就是这样做的：

Configuration cfg =
                GlobalConfiguration.loadConfiguration();
cfg.setString("state.checkpoints.dir", "file:///tmp/checkpoints/state");
env.getCheckpointConfig().enableExternalizedCheckpoints(CheckpointConfig.ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION);

这是IDE中显示的错误消息：

Exception in thread "main" org.apache.flink.runtime.client.JobExecutionException: Failed to submit job ef7050e2308a4787d983d80f3c07f55c (Long Taxi Rides (checkpointed))
    at org.apache.flink.runtime.jobmanager.JobManager.org$apache$flink$runtime$jobmanager$JobManager$$submitJob(JobManager.scala:1325)
    at org.apache.flink.runtime.jobmanager.JobManager$$anonfun$handleMessage$1.applyOrElse(JobManager.scala:447)
    at scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:36)
    at org.apache.flink.runtime.LeaderSessionMessageFilter$$anonfun$receive$1.applyOrElse(LeaderSessionMessageFilter.scala:38)
    at scala.runtime.AbstractPartialFunction.apply(AbstractPartialFunction.scala:36)
    at org.apache.flink.runtime.LogMessages$$anon$1.apply(LogMessages.scala:33)
    at org.apache.flink.runtime.LogMessages$$anon$1.apply(LogMessages.scala:28)
    at scala.PartialFunction$class.applyOrElse(PartialFunction.scala:123)
    at org.apache.flink.runtime.LogMessages$$anon$1.applyOrElse(LogMessages.scala:28)
    at akka.actor.Actor$class.aroundReceive(Actor.scala:502)
    at org.apache.flink.runtime.jobmanager.JobManager.aroundReceive(JobManager.scala:122)
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:526)
    at akka.actor.ActorCell.invoke(ActorCell.scala:495)
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:257)
    at akka.dispatch.Mailbox.run(Mailbox.scala:224)
    at akka.dispatch.Mailbox.exec(Mailbox.scala:234)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)
Caused by: java.lang.IllegalStateException: CheckpointConfig says to persist periodic checkpoints, but no checkpoint directory has been configured. You can configure configure one via key 'state.checkpoints.dir'.
    at org.apache.flink.runtime.checkpoint.CheckpointCoordinator.<init>(CheckpointCoordinator.java:211)
    at org.apache.flink.runtime.executiongraph.ExecutionGraph.enableCheckpointing(ExecutionGraph.java:478)
    at org.apache.flink.runtime.executiongraph.ExecutionGraphBuilder.buildGraph(ExecutionGraphBuilder.java:291)
    at org.apache.flink.runtime.jobmanager.JobManager.org$apache$flink$runtime$jobmanager$JobManager$$submitJob(JobManager.scala:1277)
    ... 19 more

Process finished with exit code 1

（Q2）在检查站文件中(https://ci.apache.org/projects/flink/flink-docs-release-1.4/dev/stream/state/checkpointing.html)，它说“这样，如果您的工作失败，您将有一个检查点可以恢复。”，取消的工作怎么样？新作业是继续使用现有的检查点，还是从自己的检查点开始？

Answer 1

重新从Eclipse设置检查点目录，通常我只是在设置要使用的后端时这样做，例如。

env.setStateBackend(new FsStateBackend(options.getCheckpointDir()));

重新取消作业-检查点目录被删除。如果您想在停止（取消）作业后从已知状态恢复，您需要执行保存点。

Answer 2

第一个问题，使用自定义配置创建本地环境：

val conf = new Configuration()
conf.setString(CoreOptions.CHECKPOINTS_DIRECTORY, "file:///user/flink/checkpoint/storing/")
StreamExecutionEnvironment.createLocalEnvironment(4, conf)

第二个问题，正如大卫所说：

config.enableExternalizedCheckpoints(ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION);

Answer 3

您可以控制取消作业时是否删除外部化的检查点。如果要保留它们，可以执行以下操作：

CheckpointConfig config = env.getCheckpointConfig();
config.enableExternalizedCheckpoints(ExternalizedCheckpointCleanup.RETAIN_ON_CANCELLATION);

有关详细信息，请参阅文档。

要从外部化的检查点恢复，需要执行以下操作（与从保存点恢复相同）：

$ bin/flink run -s :checkpointMetaDataPath [:runArgs]