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From Jan Urbański (JIRA) <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-11209) SSTable ancestor leaked reference
Date Fri, 26 Feb 2016 14:46:18 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-11209?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15169124#comment-15169124
] 

Jan Urbański commented on CASSANDRA-11209:
------------------------------------------

Some more bits of info with regarts to that timeline:
 * *balanced-brow* was logging LEAK DETECTED messages long before the overlapping repair error
on *radiant-hat*. It's possible that a different overlapping repair started started causing
it a long time ago
 * this cluster has four nodes in it: *balanced-brow*, *awful-bull*, *radiant-hat* and *amused-carp*
(that's the layout in token order; we're not using vnodes and have RF=2)
 * the IPs of the nodes (handy to interpret the logs) are:
{code}
balanced-brow: 10.1.29.31
awful-bull: 10.1.27.32
radiant-hat: 10.1.24.29
amused-carp: 10.1.28.32
{code}

> SSTable ancestor leaked reference
> ---------------------------------
>
>                 Key: CASSANDRA-11209
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-11209
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Compaction
>            Reporter: Jose Fernandez
>            Assignee: Marcus Eriksson
>         Attachments: screenshot-1.png, screenshot-2.png
>
>
> We're running a fork of 2.1.13 that adds the TimeWindowCompactionStrategy from [~jjirsa].
We've been running 4 clusters without any issues for many months until a few weeks ago we
started scheduling incremental repairs every 24 hours (previously we didn't run any repairs
at all).
> Since then we started noticing big discrepancies in the LiveDiskSpaceUsed, TotalDiskSpaceUsed,
and actual size of files on disk. The numbers are brought back in sync by restarting the node.
We also noticed that when this bug happens there are several ancestors that don't get cleaned
up. A restart will queue up a lot of compactions that slowly eat away the ancestors.
> I looked at the code and noticed that we only decrease the LiveTotalDiskUsed metric in
the SSTableDeletingTask. Since we have no errors being logged, I'm assuming that for some
reason this task is not getting queued up. If I understand correctly this only happens when
the reference count for the SStable reaches 0. So this is leading us to believe that something
during repairs and/or compactions is causing a reference leak to the ancestor table.



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