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Posted to issues@solr.apache.org by "Christine Poerschke (Jira)" <ji...@apache.org> on 2021/04/16 15:24:00 UTC
[jira] [Commented] (SOLR-15348) revisit MetricsHistoryHandler's
"could not obtain overseer" WARNings
[ https://issues.apache.org/jira/browse/SOLR-15348?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17323894#comment-17323894 ]
Christine Poerschke commented on SOLR-15348:
--------------------------------------------
* When considering the "Am I the overseer leader?" question there are three possible answers: yes, no and don't-know.
* The current {{MetricsHistoryHandler}} logic uses two possibilities: "yes" and "not yes" (where "not yes" covers both "no" and "don't know")
* It's not unexpected that (temporarily) no overseer leader exists e.g. during leadership transitions due to Solr instance shutdown or if the overseer experiences a GC pause longer than the {{zkClientTimeout}} timeout and therefore overseer leadership transitions to another Solr instance.
* It's also possible that the Solr instance trying to identify the overseer leader experiences a {{org.apache.zookeeper.KeeperException$SessionExpiredException}} correlated with a long GC pause.
Of course, long GC pauses are undesirable but since the current {{MetricsHistoryHandler}} logic does not differentiate between _"i do know that i am not the overseer"_ and _"i don't know who the overseer is (and will presume it's not me)"_ I think it is unnecessary and confusing to have the {{"Could not obtain overseer's address, skipping."}} logging as a WARNing and INFOrmational logging would be sufficient in the expected scenarios (KeeperException and NoSuchElementException) and only for the unexpected {{IOException}} scenario to be a WARNing.
> revisit MetricsHistoryHandler's "could not obtain overseer" WARNings
> --------------------------------------------------------------------
>
> Key: SOLR-15348
> URL: https://issues.apache.org/jira/browse/SOLR-15348
> Project: Solr
> Issue Type: Task
> Reporter: Christine Poerschke
> Assignee: Christine Poerschke
> Priority: Minor
>
> https://github.com/apache/lucene-solr/blob/releases/lucene-solr/8.8.2/solr/core/src/java/org/apache/solr/handler/admin/MetricsHistoryHandler.java#L339
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