Eros Taborelli created SOLR-11882:
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Summary: SolrMetric registries cause huge memory consumption with
lots of transient cores
Key: SOLR-11882
URL: https://issues.apache.org/jira/browse/SOLR-11882
Project: Solr
Issue Type: Bug
Security Level: Public (Default Security Level. Issues are Public)
Components: Server
Affects Versions: 7.1
Reporter: Eros Taborelli
Attachments: solr-dump-full_Leak_Suspects.zip
*Description:*
Our setup involves using a lot of small cores (possibly hundred thousand), but
working only on a few of them at any given time.
We already followed all recommendations in this guide:
[https://wiki.apache.org/solr/LotsOfCores]
We noticed that after creating/loading around 1000-2000 empty cores, with no
documents inside, the heap consumption went through the roof despite having set
transientCacheSize to only 64 (heap size set to 12G).
All cores are correctly set to loadOnStartup=false and transient=true, and we
have verified via logs that the cores in excess are actually being closed.
However, a reference remains in the
org.apache.solr.metrics.SolrMetricManager#registries that is never removed
until a core if fully unloaded.
Restarting the JVM loads all cores in the admin UI, but doesn't populate the
ConcurrentHashMap until a core is actually fully loaded.
I reproduced the issue on a smaller scale (transientCacheSize = 5, heap size =
512m) and made a report (attached) using eclipse MAT.
*Desired outcome:*
When a transient core is closed, the references in the SolrMetricManager should
be removed, in the same fashion the reporters for the core are also closed and
removed.
In alternative, a unloadOnClose=true|false flag could be implemented to fully
unload a transient core when closed due to the cache size.
*Note:*
The documentation mentions everywhere that the unused cores will be unloaded,
but it's misleading as the cores are never fully unloaded.
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