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https://issues.apache.org/jira/browse/SOLR-13884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16963353#comment-16963353
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Yonik Seeley commented on SOLR-13884:
-------------------------------------
See #987 for a test. When I run 20 concurrent single replica collection
creations, I sometimes see very skewed placement over 2 nodes. Sometimes 7 and
13 or more.
Here's the weird thing though... when I switch to doing them serially, I often
still get bad results.
To try, change
{code}
final int nThreads = 20;
final int createsPerThread = 1;
{code}
to
{code}
final int nThreads = 1;
final int createsPerThread = 20;
{code}
It helps if I add a sleep after every create, but then I still normally end up
with 11 and 9 instead of 10 replicas on each of the 2 nodes.
> Concurrent collection creation leads to unbalanced cluster
> ----------------------------------------------------------
>
> Key: SOLR-13884
> URL: https://issues.apache.org/jira/browse/SOLR-13884
> Project: Solr
> Issue Type: Bug
> Security Level: Public(Default Security Level. Issues are Public)
> Reporter: Yonik Seeley
> Priority: Major
> Time Spent: 10m
> Remaining Estimate: 0h
>
> When multiple collection creations are done concurrently, the cluster can end
> up very unbalanced, with many (or most) replicas going to a small set of
> nodes.
> This was observed on both 8.2 and master.
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