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https://issues.apache.org/jira/browse/FLINK-10225?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16635612#comment-16635612
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Pierre Zemb commented on FLINK-10225:
-------------------------------------
Cool, thanks [~till.rohrmann]! I would love to get involved into the design
document ;)
> Cannot access state from a empty taskmanager
> --------------------------------------------
>
> Key: FLINK-10225
> URL: https://issues.apache.org/jira/browse/FLINK-10225
> Project: Flink
> Issue Type: Bug
> Components: Queryable State
> Affects Versions: 1.5.3, 1.6.0
> Environment: 4tm and 1jm for now on 1.6.0
> Reporter: Pierre Zemb
> Priority: Critical
>
> Hi!
> I've started to deploy a small Flink cluster (4tm and 1jm for now on 1.6.0),
> and deployed a small job on it. Because of the current load, job is
> completely handled by a single tm. I've created a small proxy that is using
> [QueryableStateClient|https://ci.apache.org/projects/flink/flink-docs-master/api/java/org/apache/flink/queryablestate/client/QueryableStateClient.html]
> to access the current state. It is working nicely, except under certain
> circumstances. It seems to me that I can only access the state through a node
> that is holding a part of the job. Here's an example:
> * job on tm1. Pointing QueryableStateClient to tm1. State accessible
> * job still on tm1. Pointing QueryableStateClient to tm2 (for example).
> State inaccessible
> * killing tm1, job is now on tm2. State accessible
> * job still on tm2. Pointing QueryableStateClient to tm3. State inaccessible
> * adding some parallelism to spread job on tm1 and tm2. Pointing
> QueryableStateClient to either tm1 and tm2 is working
> * job still on tm1 and tm2. Pointing QueryableStateClient to tm3. State
> inaccessible
> When the state is inaccessible, I can see this (generated
> [here|https://github.com/apache/flink/blob/release-1.6/flink-queryable-state/flink-queryable-state-runtime/src/main/java/org/apache/flink/queryablestate/client/proxy/KvStateClientProxyHandler.java#L228]):
> {code:java}
> java.lang.RuntimeException: Failed request 0. Caused by:
> org.apache.flink.queryablestate.exceptions.UnknownLocationException: Could
> not retrieve location of state=repo-status of
> job=3ac3bc00b2d5bc0752917186a288d40a. Potential reasons are: i) the state is
> not ready, or ii) the job does not exist. at
> org.apache.flink.queryablestate.client.proxy.KvStateClientProxyHandler.getKvStateLookupInfo(KvStateClientProxyHandler.java:228)
> at
> org.apache.flink.queryablestate.client.proxy.KvStateClientProxyHandler.getState(KvStateClientProxyHandler.java:162)
> at
> org.apache.flink.queryablestate.client.proxy.KvStateClientProxyHandler.executeActionAsync(KvStateClientProxyHandler.java:129)
> at
> org.apache.flink.queryablestate.client.proxy.KvStateClientProxyHandler.handleRequest(KvStateClientProxyHandler.java:119)
> at
> org.apache.flink.queryablestate.client.proxy.KvStateClientProxyHandler.handleRequest(KvStateClientProxyHandler.java:63)
> at
> org.apache.flink.queryablestate.network.AbstractServerHandler$AsyncRequestTask.run(AbstractServerHandler.java:236)
> at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
> at java.util.concurrent.FutureTask.run(FutureTask.java:266) at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
> at java.lang.Thread.run(Thread.java:745)
> {code}
> Went a bit through the (master branch) code. Class KvStateClientProxy is
> holding {color:#333333}kvStateLocationOracle the key-value state location
> oracle for the given JobID. Here's the usage{color}{color:#333333}:{color}
> * {color:#333333}updateKvStateLocationOracle() in registerQueryableState()
> (TaskExecutor.java){color}
> * {color:#333333}registerQueryableState() in associateWithJobManager()
> (TaskExecutor.java){color}
> * {color:#333333}associateWithJobManager in establishJobManagerConnection
> (TaskExecutor.java){color}
> * {color:#333333}establishJobManagerConnection in jobManagerGainedLeadership
> (TaskExecutor.java){color}
> * {color:#333333}jobManagerGainedLeadership in onRegistrationSuccess
> (JobLeaderService.java){color}
> {color:#333333}It seems that the KvStateLocationOracle map is updated only
> when the task manager is part of the job. {color}
> {color:#333333}For now, we are creating a List<CompletableFuture<...>> and
> getting the first CompletableFuture.succeeded future, but that is a
> workaround.{color}
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