[jira] [Created] (FLINK-8740) Job-level metrics lost during job re-submission in HA mode

["Joshua DeWald (JIRA)" <ji...@apache.org>]

Joshua DeWald created FLINK-8740:
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             Summary: Job-level metrics lost during job re-submission in HA mode
                 Key: FLINK-8740
                 URL: https://issues.apache.org/jira/browse/FLINK-8740
             Project: Flink
          Issue Type: Bug
          Components: JobManager
    Affects Versions: 1.4.0
            Reporter: Joshua DeWald


When Flink is running in High Availability and a leader re-election occurs to the same job manager, the job is unable to register the job-level metrics due to a name collision. 

This may occur even if a different Job Manager is elected, but as it is a local JobManagerMetricsGroup which spits out the error, that is unlikely the case.

 

*Expected Behavior*

When a job is forced to re-submit due to Job Manager re-election, job-level metrics should be available in the new instance of the job (uptime, checkpoints size, checkpoint duration, etc)

*Actual Behavior*

When job gets re-submitted, it is unable to register job-level metrics due to collision in the JobManagerMetricGroup, which leads to situation where even though job is running the metrics around checkpoints and uptime are not available

*Steps to reproduce*
 # Start up Flink in HA mode using ZooKeeper, single node is fine
 # Submit a job to the cluster
 # Stop and restart ZooKeeper
 # In Job Manager logs you will see the following errors:
 # 
{noformat}
79043 2018-02-19 21:58:15,928 WARN org.apache.flink.metrics.MetricGroup - Name collision: Group already contains a Metric with the name 'totalNumberOfCheckpoints'. Metric will not be reported....
79044 2018-02-19 21:58:15,928 WARN org.apache.flink.metrics.MetricGroup - Name collision: Group already contains a Metric with the name 'numberOfInProgressCheckpoints'. Metric will not be reported....
79045 2018-02-19 21:58:15,928 WARN org.apache.flink.metrics.MetricGroup - Name collision: Group already contains a Metric with the name 'numberOfCompletedCheckpoints'. Metric will not be reported....{noformat}

*Proposed Solution*

I suspect that there may be other related issues than just the metrics, but a code change that seems to fix the issue is that, during recovery, to remove the existing registered Job Metrics:
{code:java}
if (isRecovery) {
   log.info(s"Removing metrics for $jobId, new will be added during recover")
   jobManagerMetricGroup.removeJob(jobId)
}{code}
I'd be happy to submit this in a PR if that is acceptable to open up the discussion, but I am not sure the consequences of not closing the previous JMMG or perhaps simply not re-registering job-level metrics during recovery. Doing this would seem to entail informing lower levels about the recovery.



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