[jira] [Work logged] (BEAM-9039) Fix Datachannel stuckness on errors

["ASF GitHub Bot (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/BEAM-9039?focusedWorklogId=364777&page=com.atlassian.jira.plugin.system.issuetabpanels:worklog-tabpanel#worklog-364777 ]

ASF GitHub Bot logged work on BEAM-9039:
----------------------------------------

                Author: ASF GitHub Bot
            Created on: 30/Dec/19 21:49
            Start Date: 30/Dec/19 21:49
    Worklog Time Spent: 10m 
      Work Description: lostluck commented on issue #10456: [BEAM-9039] Fix race on reading channel readErr
URL: https://github.com/apache/beam/pull/10456#issuecomment-569806113
 
 
   Thanks! I filed one as a catch all for any further stuckness issues. It should be closed with this fix, but we can re-open if we find more.
 
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Issue Time Tracking
-------------------

            Worklog Id:     (was: 364777)
    Remaining Estimate: 0h
            Time Spent: 10m

> Fix Datachannel stuckness on errors
> -----------------------------------
>
>                 Key: BEAM-9039
>                 URL: https://issues.apache.org/jira/browse/BEAM-9039
>             Project: Beam
>          Issue Type: Sub-task
>          Components: sdk-go
>    Affects Versions: Not applicable
>            Reporter: Robert Burke
>            Assignee: Robert Burke
>            Priority: Major
>             Fix For: Not applicable
>
>          Time Spent: 10m
>  Remaining Estimate: 0h
>
> Catch all task for any data channel stuckness issues, in particular if any happen on errors.
> The last known one I have is a race condition on DataChannel.readErr 
> Close off a race condition where a closing DataChannel might have new readers created for it while it is failing, causing stuckness in the bundles.
> In particular, the c.readErr must be interacted while c.mu is held.
> Otherwise something like the following happens.
> Given a channel C, and goroutines G1,G2.
>  # G1 A request for a new reader on C arrives, checks C.readErr finds it null.
>  # G2 An error occurs on reading. The lock is acquired, and C.readErr is set. Readers are closed. The channel is officially closed with A.forceRecreate, removing it from the DataManager cache.
>  # G1 calls A.makeReader, and creates a new reader there.
> There could be an arbitrary number of G1s.
>  



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