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From "ASF subversion and git services (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-13072) Management of markers for nodeLost / nodeAdded events is broken
Date Tue, 08 Jan 2019 18:14:00 GMT

    [ https://issues.apache.org/jira/browse/SOLR-13072?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16737358#comment-16737358
] 

ASF subversion and git services commented on SOLR-13072:
--------------------------------------------------------

Commit 7db4121b4553568108e1cf91e82c68fc55b6e9f4 in lucene-solr's branch refs/heads/master
from Andrzej Bialecki
[ https://git-wip-us.apache.org/repos/asf?p=lucene-solr.git;h=7db4121 ]

SOLR-13072: Use the same wait in other simulated tests where the same race condition may occur.


> Management of markers for nodeLost / nodeAdded events is broken
> ---------------------------------------------------------------
>
>                 Key: SOLR-13072
>                 URL: https://issues.apache.org/jira/browse/SOLR-13072
>             Project: Solr
>          Issue Type: Bug
>      Security Level: Public(Default Security Level. Issues are Public) 
>          Components: AutoScaling
>    Affects Versions: 7.5, 7.6, 8.0
>            Reporter: Andrzej Bialecki 
>            Assignee: Andrzej Bialecki 
>            Priority: Major
>             Fix For: 8.0, 7.7
>
>
> In order to prevent {{nodeLost}} events from being lost when it's the Overseer leader
that is the node that was lost a mechanism was added to record markers for these events by
any other live node, in {{ZkController.registerLiveNodesListener()}}. As similar mechanism
also exists for {{nodeAdded}} events.
> On Overseer leader restart if the autoscaling configuration didn't contain any triggers
that consume {{nodeLost}} events then these markers are removed. If there are 1 or more trigger
configs that consume {{nodeLost}} events then these triggers would read the markers, remove
them and generate appropriate events.
> However, as the {{NodeMarkersRegistrationTest}} shows this mechanism is broken and susceptible
to race conditions.
> It's not unusual to have more than 1 {{nodeLost}} trigger because in addition to any
user-defined triggers there's always one that is automatically defined if missing: {{.auto_add_replicas}}.
However, if there's more than 1 {{nodeLost}} trigger then the process of consuming and removing
the markers becomes non-deterministic - each trigger may pick up (and delete) all, none, or
some of the markers.
> So as it is now this mechanism is broken if more than 1 {{nodeLost}} or more than 1 {{nodeAdded}}
trigger is defined.



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