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Posted to issues@lucene.apache.org by "Andrzej Bialecki (Jira)" <ji...@apache.org> on 2020/07/28 11:54:00 UTC
[jira] [Commented] (SOLR-14657) spurious ERRORs due to race
condition between SolrIndexSearcher metrics and IndexReader closing
[ https://issues.apache.org/jira/browse/SOLR-14657?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17166366#comment-17166366 ]
Andrzej Bialecki commented on SOLR-14657:
-----------------------------------------
The same issue is present in a few other components, eg. SolrCore.initializeMetrics, although there I opted for checking whether the core is closed ... how about adding this convenience method as {{SolrMetricsContext.safeGauge(Gauge g, Object defValue) / }}{{SolrMetricsContext.safeGauge(Gauge g)}} ? At least we would have one central place to make these decisions. For this particular gauge I would be tempted to return -1 instead of null, as a kind of "impossible value" that we already return from other numeric gauges.
The {{MetricsHandler}} (or more precisely {{MetricUtils}}) knows how to handle null output from Gauges, it's simply translated to a null JSON value. Whether that's better than a fake value is another discussion, see SOLR-14683 - some clients may not be prepared to deal with {{null}} JSON values. Perhaps such values should not appear at all in the metrics output?
Anyway, in this issue we can at least refactor the code to make that decision easier.
> spurious ERRORs due to race condition between SolrIndexSearcher metrics and IndexReader closing
> -----------------------------------------------------------------------------------------------
>
> Key: SOLR-14657
> URL: https://issues.apache.org/jira/browse/SOLR-14657
> Project: Solr
> Issue Type: Improvement
> Security Level: Public(Default Security Level. Issues are Public)
> Reporter: Chris M. Hostetter
> Assignee: Chris M. Hostetter
> Priority: Major
> Attachments: SOLR-14657.patch
>
>
> I've seen situations in the wild where systems monitoring/polling metrics can trigger scary looking - but otherwise benign - ERRORs due to AlreadyClosedExceptions if/when the searcher/reader is in the process of being re-opened and the Gauge tries to call reader.numDocs(), etc...
> We should tweak the metrics logic to just ignore these exceptions
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