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https://issues.apache.org/jira/browse/CASSANDRA-9882?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14693305#comment-14693305
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Marcus Eriksson commented on CASSANDRA-9882:
--------------------------------------------
I'm not sure this is the way forward, the only(?) time we loop here is if we
fail to mark sstables as compacting, and that should be very rare. If it is not
very rare, this patch could stall compactions for 5 minutes. Perhaps we could
move the looping outside of the synchronized block though? Something like this:
https://github.com/krummas/cassandra/blob/79191d5d04d29e386855a04bfc080c49fe5a97b4/src/java/org/apache/cassandra/db/compaction/LeveledCompactionStrategy.java#L109-L157
might work?
I also really think we need to do what is in my patch above as calculating the
expired sstables can take a very long time with many sstables (does not really
matter if we loop or not if that method takes minutes to call)
> DTCS (maybe other strategies) can block flushing when there are lots of
> sstables
> --------------------------------------------------------------------------------
>
> Key: CASSANDRA-9882
> URL: https://issues.apache.org/jira/browse/CASSANDRA-9882
> Project: Cassandra
> Issue Type: Bug
> Components: Core
> Reporter: Jeremiah Jordan
> Assignee: Marcus Eriksson
> Labels: dtcs
> Fix For: 2.1.x, 2.2.x
>
>
> MemtableFlushWriter tasks can get blocked by Compaction
> getNextBackgroundTask. This is in a wonky cluster with 200k sstables in the
> CF, but seems bad for flushing to be blocked by getNextBackgroundTask when we
> are trying to make these new "smart" strategies that may take some time to
> calculate what to do.
> {noformat}
> "MemtableFlushWriter:21" daemon prio=10 tid=0x00007ff7ad965000 nid=0x6693
> waiting for monitor entry [0x00007ff78a667000]
> java.lang.Thread.State: BLOCKED (on object monitor)
> at
> org.apache.cassandra.db.compaction.WrappingCompactionStrategy.handleNotification(WrappingCompactionStrategy.java:237)
> - waiting to lock <0x00000006fcdbbf60> (a
> org.apache.cassandra.db.compaction.WrappingCompactionStrategy)
> at org.apache.cassandra.db.DataTracker.notifyAdded(DataTracker.java:518)
> at
> org.apache.cassandra.db.DataTracker.replaceFlushed(DataTracker.java:178)
> at
> org.apache.cassandra.db.compaction.AbstractCompactionStrategy.replaceFlushed(AbstractCompactionStrategy.java:234)
> at
> org.apache.cassandra.db.ColumnFamilyStore.replaceFlushed(ColumnFamilyStore.java:1475)
> at
> org.apache.cassandra.db.Memtable$FlushRunnable.runMayThrow(Memtable.java:336)
> at
> org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:28)
> at
> com.google.common.util.concurrent.MoreExecutors$SameThreadExecutorService.execute(MoreExecutors.java:297)
> at
> org.apache.cassandra.db.ColumnFamilyStore$Flush.run(ColumnFamilyStore.java:1127)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:745)
> Locked ownable synchronizers:
> - <0x0000000743b3ac38> (a
> java.util.concurrent.ThreadPoolExecutor$Worker)
> "MemtableFlushWriter:19" daemon prio=10 tid=0x00007ff7ac57a000 nid=0x649b
> waiting for monitor entry [0x00007ff78b8ee000]
> java.lang.Thread.State: BLOCKED (on object monitor)
> at
> org.apache.cassandra.db.compaction.WrappingCompactionStrategy.handleNotification(WrappingCompactionStrategy.java:237)
> - waiting to lock <0x00000006fcdbbf60> (a
> org.apache.cassandra.db.compaction.WrappingCompactionStrategy)
> at org.apache.cassandra.db.DataTracker.notifyAdded(DataTracker.java:518)
> at
> org.apache.cassandra.db.DataTracker.replaceFlushed(DataTracker.java:178)
> at
> org.apache.cassandra.db.compaction.AbstractCompactionStrategy.replaceFlushed(AbstractCompactionStrategy.java:234)
> at
> org.apache.cassandra.db.ColumnFamilyStore.replaceFlushed(ColumnFamilyStore.java:1475)
> at
> org.apache.cassandra.db.Memtable$FlushRunnable.runMayThrow(Memtable.java:336)
> at
> org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:28)
> at
> com.google.common.util.concurrent.MoreExecutors$SameThreadExecutorService.execute(MoreExecutors.java:297)
> at
> org.apache.cassandra.db.ColumnFamilyStore$Flush.run(ColumnFamilyStore.java:1127)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:745)
> "CompactionExecutor:14" daemon prio=10 tid=0x00007ff7ad359800 nid=0x4d59
> runnable [0x00007fecce3ea000]
> java.lang.Thread.State: RUNNABLE
> at
> org.apache.cassandra.io.sstable.SSTableReader.equals(SSTableReader.java:628)
> at
> com.google.common.collect.ImmutableSet.construct(ImmutableSet.java:206)
> at
> com.google.common.collect.ImmutableSet.construct(ImmutableSet.java:220)
> at
> com.google.common.collect.ImmutableSet.access$000(ImmutableSet.java:74)
> at
> com.google.common.collect.ImmutableSet$Builder.build(ImmutableSet.java:531)
> at com.google.common.collect.Sets$1.immutableCopy(Sets.java:606)
> at
> org.apache.cassandra.db.ColumnFamilyStore.getOverlappingSSTables(ColumnFamilyStore.java:1352)
> at
> org.apache.cassandra.db.compaction.DateTieredCompactionStrategy.getNextBackgroundSSTables(DateTieredCompactionStrategy.java:88)
> at
> org.apache.cassandra.db.compaction.DateTieredCompactionStrategy.getNextBackgroundTask(DateTieredCompactionStrategy.java:65)
> - locked <0x00000006fcdbbf00> (a
> org.apache.cassandra.db.compaction.DateTieredCompactionStrategy)
> at
> org.apache.cassandra.db.compaction.WrappingCompactionStrategy.getNextBackgroundTask(WrappingCompactionStrategy.java:72)
> - locked <0x00000006fcdbbf60> (a
> org.apache.cassandra.db.compaction.WrappingCompactionStrategy)
> at
> org.apache.cassandra.db.compaction.CompactionManager$BackgroundCompactionTask.run(CompactionManager.java:238)
> at
> java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:471)
> at java.util.concurrent.FutureTask.run(FutureTask.java:262)
> at
> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
> at
> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
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