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Posted to issues-all@impala.apache.org by "Wenzhe Zhou (Jira)" <ji...@apache.org> on 2023/08/19 05:46:00 UTC
[jira] [Commented] (IMPALA-12382) Coordinator could schedule fragments on gracefully shutdown executors
[ https://issues.apache.org/jira/browse/IMPALA-12382?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17756237#comment-17756237 ]
Wenzhe Zhou commented on IMPALA-12382:
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We could add UnregisterSubscriber API in StatestoreService. The executors which are being shutdown gracefully could send unregistration request to statestore so that statestore could remove the executors from cluster membership. Another approach is to let executors to report their states to statestore in the response message of heartbeat when executors are shutdown.
> Coordinator could schedule fragments on gracefully shutdown executors
> ---------------------------------------------------------------------
>
> Key: IMPALA-12382
> URL: https://issues.apache.org/jira/browse/IMPALA-12382
> Project: IMPALA
> Issue Type: Improvement
> Reporter: Abhishek Rawat
> Priority: Critical
>
> Statestore does failure detection based on consecutive heartbeat failures. This is by default configured to be 10 (statestore_max_missed_heartbeats) at 1 second intervals (statestore_heartbeat_frequency_ms). This could however take much longer than 10 seconds overall, especially if statestore is busy and due to rpc timeout duration.
> In the following example it took 50 seconds for failure detection:
> {code:java}
> I0817 12:32:06.824721 86 statestore.cc:1157] Unable to send heartbeat message to subscriber impalad@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010, received error: RPC Error: Client for 10.80.199.159:23000 hit an unexpected exception: No more data to read., type: N6apache6thrift9transport19TTransportExceptionE, rpc: N6impala18THeartbeatResponseE, send: done
> I0817 12:32:06.824741 86 failure-detector.cc:91] 1 consecutive heartbeats failed for 'impalad@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010'. State is OK
> .....
> .....
> .....
> I0817 12:32:56.800251 83 statestore.cc:1157] Unable to send heartbeat message to subscriber impalad@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010, received error: RPC Error: Client for 10.80.199.159:23000 hit an unexpected exception: No more data to read., type: N6apache6thrift9transport19TTransportExceptionE, rpc: N6impala18THeartbeatResponseE, send: done
> I0817 12:32:56.800267 83 failure-detector.cc:91] 10 consecutive heartbeats failed for 'impalad@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010'. State is FAILED
> I0817 12:32:56.800276 83 statestore.cc:1168] Subscriber 'impalad@impala-executor-001-5.impala-executor.impala-1692115218-htqx.svc.cluster.local:27010' has failed, disconnected or re-registered (last known registration ID: c84bf70f03acda2b:b34a812c5e96e687){code}
> As a result there is a window when statestore is determining node failure and coordinator might schedule fragments on that particular executor(s). The exec RPC will fail and if transparent query retries is enabled, coordinator will immediately retry the query and it will fail again.
> Ideally in such situations coordinator should be notified sooner about a failed executor. Statestore could send priority topic update to coordinator when it enters failure detection logic. This should reduce the chances of coordinator scheduling query fragment on a failed executor.
> The other argument could be to tune the heartbeat frequency and interval parameters. But, it's hard to find configuration which works for all cases. And, so while the default values are reasonable, under certain conditions they could be unreasonable as seen in the above example.
> It might make sense to especially handle the case where executors are shutdown gracefully and in such case statestore shouldn't do failure detection and instead fail these executor immediately.
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