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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Work logged] (BEAM-5110) Reconile Flink JVM singleton management with deployment
Date Fri, 10 Aug 2018 13:08:00 GMT

     [ https://issues.apache.org/jira/browse/BEAM-5110?focusedWorklogId=133574&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-133574
]

ASF GitHub Bot logged work on BEAM-5110:
----------------------------------------

                Author: ASF GitHub Bot
            Created on: 10/Aug/18 13:07
            Start Date: 10/Aug/18 13:07
    Worklog Time Spent: 10m 
      Work Description: tweise commented on issue #6189: [BEAM-5110] Explicitly count the
references for BatchFlinkExecutableStageContext …
URL: https://github.com/apache/beam/pull/6189#issuecomment-412076686
 
 
   See comment on https://jira.apache.org/jira/browse/BEAM-5110

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Issue Time Tracking
-------------------

    Worklog Id:     (was: 133574)
    Time Spent: 1h 50m  (was: 1h 40m)

> Reconile Flink JVM singleton management with deployment
> -------------------------------------------------------
>
>                 Key: BEAM-5110
>                 URL: https://issues.apache.org/jira/browse/BEAM-5110
>             Project: Beam
>          Issue Type: Bug
>          Components: runner-flink
>            Reporter: Ben Sidhom
>            Assignee: Ben Sidhom
>            Priority: Major
>          Time Spent: 1h 50m
>  Remaining Estimate: 0h
>
> [~angoenka] noticed through debugging that multiple instances of BatchFlinkExecutableStageContext.BatchFactory
are loaded for a given job when executing in standalone cluster mode. This context factory
is responsible for maintaining singleton state across a TaskManager (JVM) in order to share
SDK Environments across workers in a given job. The multiple-loading breaks singleton semantics
and results in an indeterminate number of Environments being created.
> It turns out that the [Flink classloading mechanism|https://ci.apache.org/projects/flink/flink-docs-release-1.5/monitoring/debugging_classloading.html]
is determined by deployment mode. Note that "user code" as referenced by this link is actually
the Flink job server jar. Actual end-user code lives inside of the SDK Environment and uploaded
artifacts.
> In order to maintain singletons without resorting to IPC (for example, using file locks
and/or additional gRPC servers), we need to force non-dynamic classloading. For example,
this happens when jobs are submitted to YARN for one-off deployments via `flink run`. However,
connecting to an existing (Flink standalone) deployment results in dynamic classloading.
> We should investigate this behavior and either document (and attempt to enforce) deployment
modes that are consistent with our requirements, or (if possible) create a custom classloader
that enforces singleton loading.



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