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From "Paulo Motta (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-13948) Avoid deadlock when not able to acquire references for compaction
Date Thu, 19 Oct 2017 15:55:01 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-13948?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16211253#comment-16211253
] 

Paulo Motta commented on CASSANDRA-13948:
-----------------------------------------

bq. we should probably fix that instead (or, as well) - flushing sstables also depends on
the boundaries, and we can't delay that until gossip has settled (commitlog replay might have
to flush)

The reason why the ring boundaries were not computed correctly on startup was because the
{{GossipingPropertyFileSnitch}} did not have rack/dc info about all nodes on gossip so it
fallback to the sample {{conf/cassandra-rackdc.properties}} file from {{PropertyFileSnitch}}
so I created CASSANDRA-13970 to fix that.

In any case, even with that fixed, the {{CompactionStrategyManager}} (CSM) does not reload
its compaction strategies when the disk boundaries are updated (either because of range movements,
when the node first joins the ring, or a disk breaks) what can cause {{CompactionStrategyManager.getCompactionStrategyIndex}}
to return a different sstable->disk assignment to the one currently on the CSM, so some
SStables may not be correctly updated in the compaction strategies after being updated/replaced/removed.
 Perhaps this is better illustrated by [this test|https://github.com/pauloricardomg/cassandra/commit/073bfa4e548ac807b523a919288a5a71379bfd21#diff-f9c882c974db60a710cf1f195cfdb801R95].

So it shouldn't be a problem if on a race with gossip flush writes an SSTable to a wrong disk,
as long as after the boundary is updated, the SSTable is placed on the correct compaction
strategy and its compaction output will be placed in the correct disk (should probably add
a test with this scenario).

Also this is a bit orthogonal to CASSANDRA-13215 - the objective there is to cache the disk
boundary computation, while here is to make sure CSM can gracefully handle boundary changes.

> Avoid deadlock when not able to acquire references for compaction
> -----------------------------------------------------------------
>
>                 Key: CASSANDRA-13948
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-13948
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Compaction
>            Reporter: Paulo Motta
>            Assignee: Paulo Motta
>             Fix For: 3.11.x, 4.x
>
>         Attachments: debug.log
>
>
> The thread dump below shows a race between an sstable replacement by the {{IndexSummaryRedistribution}}
and {{AbstractCompactionTask.getNextBackgroundTask}}:
> {noformat}
> Thread 94580: (state = BLOCKED)
>  - sun.misc.Unsafe.park(boolean, long) @bci=0 (Compiled frame; information may be imprecise)
>  - java.util.concurrent.locks.LockSupport.park(java.lang.Object) @bci=14, line=175 (Compiled
frame)
>  - java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt() @bci=1,
line=836 (Compiled frame)
>  - java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(java.util.concurrent.locks.AbstractQueuedSynchronizer$Node,
int) @bci=67, line=870 (Compiled frame)
>  - java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(int) @bci=17, line=1199
(Compiled frame)
>  - java.util.concurrent.locks.ReentrantReadWriteLock$WriteLock.lock() @bci=5, line=943
(Compiled frame)
>  - org.apache.cassandra.db.compaction.CompactionStrategyManager.handleListChangedNotification(java.lang.Iterable,
java.lang.Iterable) @bci=359, line=483 (Interpreted frame)
>  - org.apache.cassandra.db.compaction.CompactionStrategyManager.handleNotification(org.apache.cassandra.notifications.INotification,
java.lang.Object) @bci=53, line=555 (Interpreted frame)
>  - org.apache.cassandra.db.lifecycle.Tracker.notifySSTablesChanged(java.util.Collection,
java.util.Collection, org.apache.cassandra.db.compaction.OperationType, java.lang.Throwable)
@bci=50, line=409 (Interpreted frame)
>  - org.apache.cassandra.db.lifecycle.LifecycleTransaction.doCommit(java.lang.Throwable)
@bci=157, line=227 (Interpreted frame)
>  - org.apache.cassandra.utils.concurrent.Transactional$AbstractTransactional.commit(java.lang.Throwable)
@bci=61, line=116 (Compiled frame)
>  - org.apache.cassandra.utils.concurrent.Transactional$AbstractTransactional.commit()
@bci=2, line=200 (Interpreted frame)
>  - org.apache.cassandra.utils.concurrent.Transactional$AbstractTransactional.finish()
@bci=5, line=185 (Interpreted frame)
>  - org.apache.cassandra.io.sstable.IndexSummaryRedistribution.redistributeSummaries()
@bci=559, line=130 (Interpreted frame)
>  - org.apache.cassandra.db.compaction.CompactionManager.runIndexSummaryRedistribution(org.apache.cassandra.io.sstable.IndexSummaryRedistribution)
@bci=9, line=1420 (Interpreted frame)
>  - org.apache.cassandra.io.sstable.IndexSummaryManager.redistributeSummaries(org.apache.cassandra.io.sstable.IndexSummaryRedistribution)
@bci=4, line=250 (Interpreted frame)
>  - org.apache.cassandra.io.sstable.IndexSummaryManager.redistributeSummaries() @bci=30,
line=228 (Interpreted frame)
>  - org.apache.cassandra.io.sstable.IndexSummaryManager$1.runMayThrow() @bci=4, line=125
(Interpreted frame)
>  - org.apache.cassandra.utils.WrappedRunnable.run() @bci=1, line=28 (Interpreted frame)
>  - org.apache.cassandra.concurrent.DebuggableScheduledThreadPoolExecutor$UncomplainingRunnable.run()
@bci=4, line=118 (Compiled frame)
>  - java.util.concurrent.Executors$RunnableAdapter.call() @bci=4, line=511 (Compiled frame)
>  - java.util.concurrent.FutureTask.runAndReset() @bci=47, line=308 (Compiled frame)
>  - java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask)
@bci=1, line=180 (Compiled frame)
>  - java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run() @bci=37,
line=294 (Compiled frame)
>  - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker)
@bci=95, line=1149 (Compiled frame)
>  - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=624 (Interpreted
frame)
>  - org.apache.cassandra.concurrent.NamedThreadFactory.lambda$threadLocalDeallocator$0(java.lang.Runnable)
@bci=1, line=81 (Interpreted frame)
>  - org.apache.cassandra.concurrent.NamedThreadFactory$$Lambda$8.run() @bci=4 (Interpreted
frame)
>  - java.lang.Thread.run() @bci=11, line=748 (Compiled frame)
> {noformat}
> {noformat}
> Thread 94573: (state = IN_JAVA)
>  - java.util.HashMap$HashIterator.nextNode() @bci=95, line=1441 (Compiled frame; information
may be imprecise)
>  - java.util.HashMap$KeyIterator.next() @bci=1, line=1461 (Compiled frame)
>  - org.apache.cassandra.db.lifecycle.View$3.apply(org.apache.cassandra.db.lifecycle.View)
@bci=20, line=268 (Compiled frame)
>  - org.apache.cassandra.db.lifecycle.View$3.apply(java.lang.Object) @bci=5, line=265
(Compiled frame)
>  - org.apache.cassandra.db.lifecycle.Tracker.apply(com.google.common.base.Predicate,
com.google.common.base.Function) @bci=13, line=133 (Compiled frame)
>  - org.apache.cassandra.db.lifecycle.Tracker.tryModify(java.lang.Iterable, org.apache.cassandra.db.compaction.OperationType)
@bci=31, line=99 (Compiled frame)
>  - org.apache.cassandra.db.compaction.LeveledCompactionStrategy.getNextBackgroundTask(int)
@bci=84, line=139 (Compiled frame)
>  - org.apache.cassandra.db.compaction.CompactionStrategyManager.getNextBackgroundTask(int)
@bci=105, line=119 (Interpreted frame)
>  - org.apache.cassandra.db.compaction.CompactionManager$BackgroundCompactionCandidate.run()
@bci=84, line=265 (Interpreted frame)
>  - java.util.concurrent.Executors$RunnableAdapter.call() @bci=4, line=511 (Compiled frame)
>  - java.util.concurrent.FutureTask.run() @bci=42, line=266 (Compiled frame)
>  - java.util.concurrent.ThreadPoolExecutor.runWorker(java.util.concurrent.ThreadPoolExecutor$Worker)
@bci=95, line=1149 (Compiled frame)
>  - java.util.concurrent.ThreadPoolExecutor$Worker.run() @bci=5, line=624 (Interpreted
frame)
>  - org.apache.cassandra.concurrent.NamedThreadFactory.lambda$threadLocalDeallocator$0(java.lang.Runnable)
@bci=1, line=81 (Interpreted frame)
>  - org.apache.cassandra.concurrent.NamedThreadFactory$$Lambda$8.run() @bci=4 (Interpreted
frame)
>  - java.lang.Thread.run() @bci=11, line=748 (Compiled frame)
> {noformat}
> This particular node remain in this state forever, indicating {{LeveledCompactionStrategyTask.getNextBackgroundTask}}
was looping indefinitely.
> What happened is that sstable references were replaced on the tracker by the {{IndexSummaryRedistribution}}
thread, so the {{AbstractCompactionStrategy.getNextBackgroundTask}} could not create the transaction
with the old references, and the {{IndexSummaryRedistribution}} could not update the sstable
reference in the compaction strategy because {{AbstractCompactionStrategy.getNextBackgroundTask}}
was holding the {{CompactionStrategyManager}} lock.



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