[jira] [Created] (AMBARI-21593) cp /tmp/ambari-metrics-timelineservice-2.5.1.0.0.jar /usr/lib/ambari-metrics-collector/ambari-metrics-timelineservice-2.5.2.0.191.jar

["Aravindan Vijayan (JIRA)" <ji...@apache.org>]

Aravindan Vijayan created AMBARI-21593:
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             Summary: cp /tmp/ambari-metrics-timelineservice-2.5.1.0.0.jar /usr/lib/ambari-metrics-collector/ambari-metrics-timelineservice-2.5.2.0.191.jar
                 Key: AMBARI-21593
                 URL: https://issues.apache.org/jira/browse/AMBARI-21593
             Project: Ambari
          Issue Type: Bug
          Components: ambari-metrics
    Affects Versions: 2.5.2
            Reporter: Aravindan Vijayan
            Assignee: Aravindan Vijayan
            Priority: Blocker
             Fix For: 2.5.2


PROBLEM
When 2 metric collectors are started up simultaneously, both of them fail to start.

BUG
There exists a race condition in the Metric Collector HA controller initialization which was introduced through AMBARI-20179. When a helix controller instance finds that the /ambari-metrics-collector znode exists but a child node does not exists, it deletes the entire znode and recreates. If another controller instance also initializes simultaneously, a race condition can occur wherein each instance will end up cancelling the effort of the other. 

FIX
Do not delete and recreate the znode. Wait and retry for a few seconds to check if /ambari-metrics-collector was fully initailized. 




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