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https://issues.apache.org/jira/browse/CASSANDRA-14164?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16326897#comment-16326897
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Ignace Desimpel commented on CASSANDRA-14164:
---------------------------------------------
I was testing the an automated restore of datafiles of a keyspace in an
embedded cassandra application. Nothing else was running.
Based on what you said about initCf : Before restoring the datafiles, an
embedded call to Keyspace.clear() was made to avoid any open handles, and then
to delete and replace all files. That will be the reason why it is opened the
first time.
I probably can find a way arround it, leaving the theoretical locking issue.
> Calling StorageService.loadNewSSTables function results in deadlock with
> compaction background task
> ---------------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-14164
> URL: https://issues.apache.org/jira/browse/CASSANDRA-14164
> Project: Cassandra
> Issue Type: Bug
> Components: Compaction, Tools
> Environment: code
> Reporter: Ignace Desimpel
> Assignee: Marcus Eriksson
> Priority: Major
> Fix For: 2.2.x, 3.0.x
>
> Attachments: Stack1.txt
>
>
> Tested on version 2.2.11 (but seems like trunck 3.x is still the same for the
> related code path), using nodetool refresh for restoring a snapshot
> Calling StorageService.loadNewSSTables function results in deadlock with
> compaction background task.
> because :
> From StorageService class , function public void loadNewSSTables(String
> ksName, String cfName) a call is made to ColumnFamilyStore class , function
> public static synchronized void loadNewSSTables(String ksName, String cfName)
> and then a call to Keyspace class, function public static Keyspace
> open(String keyspaceName)
> getting to the function private static Keyspace open(String keyspaceName,
> Schema schema, boolean loadSSTables)
> finally trying to get a lock by synchronized (Keyspace.class)
> So inside the ColumnFamilyStore class lock, there is an attempt to get the
> lock on the Keyspace.class
> Now at the same time I have the thread OptionalTasks executing the
> ColumnFamilyStore.getBackgroundCompactionTaskSubmitter() task.
> The thread task is also calling Keyspace.open function, already progressed as
> far as getting the lock on Keyspace class.
> But then the call also initializes the column families and thus is calling on
> class ColumnFamilyStore the public static synchronized ColumnFamilyStore
> createColumnFamilyStore ...
> Result : the external call on loadNewSSTables blocks the internal compaction
> background task.
> So function 1 locks A and then B
> And function 2 locks B and then A
> leading to deadlock (due to incorrect order of locking objects)
> Regards,
> Ignace
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