Hieu Ngo created CASSANDRA-20607:
------------------------------------
Summary: Gossip thread slows down when forceBlockingFlush is
called on system.peers and system.peers_v2 tables
Key: CASSANDRA-20607
URL: https://issues.apache.org/jira/browse/CASSANDRA-20607
Project: Apache Cassandra
Issue Type: Bug
Reporter: Hieu Ngo
The metrics system at Dropbox.com (Vortex2) uses cassandra as the data storage
layer to store metric and metadata data. The system is undergoing a migration
project to move cassandra hosted on premise to an in-house kubernetes-based
deployment system.
Whenever a pod running cassandra is rotated out during a deployment, we have
seen many nodes deemed as Down Normal pretty much at the same time for a brief
period (15 - 30s), resulting in excessive hints created, timed out and
unavailable exceptions.
It turns out that the bug is at the forceBlockingFlush call on system.peers and
system.peers_v2 tables happening within the single-threaded Gossip Stage. The
flush takes too long, occupying the Gossip STage and causing gossip tasks to
pile up. Since gossip tasks aren't sent properly and timely, nodes in the
system start marking other nodes as Down Normal. From the stack trace, we
believe the forceBlockFlush is called as part of the host ip update when the
rotated pod changes its IP.
We have created a patch internally to change the flush to nonBlockingFlush if
the flag cassandra.load_ring_state=false. The rationale for the fix is that
since the ring state isn't loaded from those peers tables during startup, there
is no need to wait for the flush. However, we haven't figured out why the
blocking flush to system.peers and system.peers_v2 tables takes so long.
The asks for this bug is:
1. Figure out why blocking flush to system.peers and system.peers_v2 tables
takes so long.
2. Create a fix to change the flush to non-blocking if
cassandra.load_ring_state is set to false. We notice that the
cassandra.load_ring_state is removed in cassandra 5.0 so the fix may only be
applicable to 4.x and older versions.
Here is the stack trace of GossipStage:
"GossipStage:1" #205 daemon prio=5 os_prio=0 cpu=113114.96ms elapsed=233376.38s
tid=0x00007fad2002c480 nid=0x3a5 waiting on condition [0x00007faf9613d000]
java.lang.Thread.State: WAITING (parking)
at jdk.internal.misc.Unsafe.park(java.base@11.0.25/Native Method)
at
java.util.concurrent.locks.LockSupport.park(java.base@11.0.25/LockSupport.java:323)
at
org.apache.cassandra.utils.concurrent.WaitQueue$Standard$AbstractSignal.await(WaitQueue.java:289)
at
org.apache.cassandra.utils.concurrent.WaitQueue$Standard$AbstractSignal.await(WaitQueue.java:282)
at
org.apache.cassandra.utils.concurrent.Awaitable$AsyncAwaitable.await(Awaitable.java:306)
at
org.apache.cassandra.utils.concurrent.AsyncFuture.await(AsyncFuture.java:154)
at
org.apache.cassandra.utils.concurrent.AsyncFuture.await(AsyncFuture.java:46)
at
org.apache.cassandra.utils.concurrent.AbstractFuture.get(AbstractFuture.java:245)
at
org.apache.cassandra.utils.FBUtilities.waitOnFutures(FBUtilities.java:501)
at
org.apache.cassandra.utils.FBUtilities.waitOnFutures(FBUtilities.java:477)
at
org.apache.cassandra.db.SystemKeyspace.forceBlockingFlush(SystemKeyspace.java:947)
at
org.apache.cassandra.db.SystemKeyspace.removeEndpoint(SystemKeyspace.java:916)
- locked <0x0000000101dfccc0> (a java.lang.Class for
org.apache.cassandra.db.SystemKeyspace)
at
org.apache.cassandra.service.StorageService.removeEndpoint(StorageService.java:3339)
at
org.apache.cassandra.service.StorageService.updateTokenMetadata(StorageService.java:3052)
at
org.apache.cassandra.service.StorageService.handleStateNormal(StorageService.java:3176)
at
org.apache.cassandra.service.StorageService.onChange(StorageService.java:2638)
at
org.apache.cassandra.gms.Gossiper.doOnChangeNotifications(Gossiper.java:1711)
at
org.apache.cassandra.service.StorageService.onJoin(StorageService.java:3652)
at
org.apache.cassandra.gms.Gossiper.handleMajorStateChange(Gossiper.java:1481)
at
org.apache.cassandra.gms.Gossiper.applyStateLocally(Gossiper.java:1627)
at
org.apache.cassandra.gms.GossipDigestAck2VerbHandler.doVerb(GossipDigestAck2VerbHandler.java:50)
at
org.apache.cassandra.net.InboundSink.lambda$new$0(InboundSink.java:78)
at
org.apache.cassandra.net.InboundSink$$Lambda$603/0x000000080069c040.accept(Unknown
Source)
at org.apache.cassandra.net.InboundSink.accept(InboundSink.java:97)
at org.apache.cassandra.net.InboundSink.accept(InboundSink.java:45)
at
org.apache.cassandra.net.InboundMessageHandler$ProcessMessage.run(InboundMessageHandler.java:430)
at
org.apache.cassandra.concurrent.ExecutionFailure$1.run(ExecutionFailure.java:133)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@11.0.25/ThreadPoolExecutor.java:1128)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@11.0.25/ThreadPoolExecutor.java:628)
at
io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.lang.Thread.run(java.base@11.0.25/Thread.java:829)
Here is the PerDiskMemtableFlushWriter that the GossipStage was waiting for:
"PerDiskMemtableFlushWriter_0:470" #170632 daemon prio=5 os_prio=0
cpu=42316.16ms elapsed=44.53s tid=0x00007faee40c91c0 nid=0x79f5 runnable
[0x00007faf70613000]
java.lang.Thread.State: RUNNABLE
at
org.apache.cassandra.db.marshal.AbstractType.writeValue(AbstractType.java:469)
at
org.apache.cassandra.db.ClusteringPrefix$Serializer.serializeValuesWithoutSize(ClusteringPrefix.java:397)
at
org.apache.cassandra.db.Clustering$Serializer.serialize(Clustering.java:133)
at
org.apache.cassandra.db.rows.UnfilteredSerializer.serialize(UnfilteredSerializer.java:188)
at
org.apache.cassandra.db.rows.UnfilteredSerializer.serialize(UnfilteredSerializer.java:137)
at org.apache.cassandra.db.ColumnIndex.add(ColumnIndex.java:258)
at
org.apache.cassandra.db.ColumnIndex.buildRowIndex(ColumnIndex.java:122)
at
org.apache.cassandra.io.sstable.format.big.BigTableWriter.append(BigTableWriter.java:222)
at
org.apache.cassandra.io.sstable.SimpleSSTableMultiWriter.append(SimpleSSTableMultiWriter.java:48)
at
org.apache.cassandra.db.memtable.Flushing$FlushRunnable.writeSortedContents(Flushing.java:163)
at
org.apache.cassandra.db.memtable.Flushing$FlushRunnable.call(Flushing.java:183)
at
org.apache.cassandra.db.memtable.Flushing$FlushRunnable.call(Flushing.java:122)
at org.apache.cassandra.concurrent.FutureTask.call(FutureTask.java:61)
at org.apache.cassandra.concurrent.FutureTask.run(FutureTask.java:71)
at
java.util.concurrent.ThreadPoolExecutor.runWorker(java.base@11.0.25/ThreadPoolExecutor.java:1128)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(java.base@11.0.25/ThreadPoolExecutor.java:628)
at
io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.lang.Thread.run(java.base@11.0.25/Thread.java:829)
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