[jira] [Created] (FLINK-21309) Metrics of JobManager and TaskManager overwrite each other in pushgateway

["jiguodai (Jira)" <ji...@apache.org>]

jiguodai created FLINK-21309:
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             Summary: Metrics of JobManager and TaskManager overwrite each other in pushgateway
                 Key: FLINK-21309
                 URL: https://issues.apache.org/jira/browse/FLINK-21309
             Project: Flink
          Issue Type: Bug
          Components: Runtime / Metrics
    Affects Versions: 1.11.0, 1.10.0, 1.9.0
         Environment: 1. Components :

Flink 1.9.0/1.10.0/1.11.0 + Prometheus + Pushgateway + Yarn

2. Metrics Configuration in flink-conf.yaml :
{code:java}
metrics.reporter.promgateway.class: org.apache.flink.metrics.prometheus.PrometheusPushGatewayReporter
metrics.reporter.promgateway.jobName: myjob
metrics.reporter.promgateway.randomJobNameSuffix: false{code}
 
            Reporter: jiguodai
         Attachments: image-2021-02-05-21-07-42-292.png

    When a flink job run on yarn, metrics of jobmanager and taskmanagers will overwrite each other. The  phenomenon is that on one second you can find only jobmanager metrics on pushgateway web ui,  while on the next second you can find only taskmanager metrics on pushgateway web ui, these two kinds of metrics appear alternately. One metric of taskmanager on grafana will be like below intermittently (this taskmanager metric disappear on grafana when jobmanager metrics overwrite taskmanager metrics):

!image-2021-02-05-21-07-42-292.png!

    The real reason is that Flink PrometheusPushGatewayReporter use PUT style instead of POST style to push metrics to pushgateway, what's more, taskmanagers and jobmanager use the same jobName (the only grouping key) which we configured in flink-conf.yaml. 

    Althought REST URLs are same as below, 
{code:java}
/metrics/job/<JOB_NAME>{/<LABEL_NAME>/<LABEL_VALUE>}
{code}
PUT and POST caused different results, as we can see below :
 * PUT is used to push a group of metrics. All metrics with the grouping key specified in the URL are replaced by the metrics pushed with PUT.
 * POST works exactly like the PUT method but only metrics with the same name as the newly pushed metrics are replaced.

    For these reasons, it's better to use POST style to push metrics to pushgateway to prevent jobmanager metrics and taskmanager metrics from overwriting each other, so that we can get continuous graph on grafana.

    Everytime some body ask why metrics on grafana is discontinuous on Flink mailing list, i will tell him that you should change the style of pushing metrics to pushgateway from PUT to POST and then repackage the flink-metrics-prometheus module. So, why don't we solve the problem permanently now ? I hope to have the chance to solve the problem, sincerely.



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