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From "Uwe Schindler (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SOLR-3685) Solr Cloud sometimes skipped peersync attempt and replicated instead due to tlog flags not being cleared when no updates were buffered during a previous replication.
Date Wed, 22 Aug 2012 16:41:43 GMT

    [ https://issues.apache.org/jira/browse/SOLR-3685?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13439666#comment-13439666
] 

Uwe Schindler commented on SOLR-3685:
-------------------------------------

Hi,
another thing to take into account: Java allocates on Linux for every thread a thread-local
amount of memory (you can see this in the pmap output as additional "[ anon ]" mappings with
a fixed size - it is only strange that you pmap does not populate the first hunman-readable
column; I think you used -x instead of no option). This sums up to a lot of memory!

See http://mail.openjdk.java.net/pipermail/hotspot-compiler-dev/2012-August/008270.html (I
don't think it is 64 MB, but for sure 1 MB)

On my machine, the threads take each 1 MB. Depending on your Tomcat config and its thread
pools this can take lot of memory, too.
                
> Solr Cloud sometimes skipped peersync attempt and replicated instead due to tlog flags
not being cleared when no updates were buffered during a previous replication.
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: SOLR-3685
>                 URL: https://issues.apache.org/jira/browse/SOLR-3685
>             Project: Solr
>          Issue Type: Bug
>          Components: replication (java), SolrCloud
>    Affects Versions: 4.0-ALPHA
>         Environment: Debian GNU/Linux Squeeze 64bit
> Solr 5.0-SNAPSHOT 1365667M - markus - 2012-07-25 19:09:43
>            Reporter: Markus Jelsma
>            Assignee: Yonik Seeley
>            Priority: Critical
>             Fix For: 4.0, 5.0
>
>         Attachments: info.log, oom-killer.log, pmap.log
>
>
> There's a serious problem with restarting nodes, not cleaning old or unused index directories
and sudden replication and Java being killed by the OS due to excessive memory allocation.
Since SOLR-1781 was fixed index directories get cleaned up when a node is being restarted
cleanly, however, old or unused index directories still pile up if Solr crashes or is being
killed by the OS, happening here.
> We have a six-node 64-bit Linux test cluster with each node having two shards. There's
512MB RAM available and no swap. Each index is roughly 27MB so about 50MB per node, this fits
easily and works fine. However, if a node is being restarted, Solr will consistently crash
because it immediately eats up all RAM. If swap is enabled Solr will eat an additional few
100MB's right after start up.
> This cannot be solved by restarting Solr, it will just crash again and leave index directories
in place until the disk is full. The only way i can restart a node safely is to delete the
index directories and have it replicate from another node. If i then restart the node it will
crash almost consistently.
> I'll attach a log of one of the nodes.

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