Haibo Sun created RATIS-2116:
--------------------------------
Summary: Follower state synchronization is blocked
Key: RATIS-2116
URL: https://issues.apache.org/jira/browse/RATIS-2116
Project: Ratis
Issue Type: Bug
Affects Versions: 3.0.1, 2.5.1, 3.0.0
Reporter: Haibo Sun
Using version 2.5.1, we have discovered that in some cases, the state
synchronization of the follower will be permanently blocked.
Scenario: When the task queue of the SegmentedRaftLogWorker is the pattern
(WriteLog, WriteLog, ..., PurgeLog), the last WriteLog of
RaftServerImpl.appendEntries does not immediately flush data and complete the
result future, because there is a pending PurgeLog task in the queue. It
enqueues the result future to be completed
after the latter WriteLog flushes data. However, the "nioEventLoopGroup-3-1"
thread is already blocked, and will not add new WriteLog to the task queue of
SegmentedRaftLogWorker. This leads to a deadlock and causes the state
synchronization to stop.
I confirmed this by adding debug logs, detailed information is attached below.
This issue can be easily reproduced by increasing the frequency of TakeSnapshot
and PurgeLog operations. In addition, after checking the code in the master
branch, this issue still exists.
*jstack:*
"nioEventLoopGroup-3-1" #58 prio=10 os_prio=0 tid=0x00007fc58400b800
nid=0x5493a waiting on condition [0x00007fc5b4f28000]
java.lang.Thread.State: WAITING (parking)
at sun.misc.Unsafe.park0(Native Method)
- parking to wait for <0x00007fd86a4685e8> (a
java.util.concurrent.CompletableFuture$Signaller)
at sun.misc.Unsafe.park(Unsafe.java:1025)
at java.util.concurrent.locks.LockSupport.park(LockSupport.java:176)
at
java.util.concurrent.CompletableFuture$Signaller.block(CompletableFuture.java:1693)
at java.util.concurrent.ForkJoinPool.managedBlock(ForkJoinPool.java:3323)
at
java.util.concurrent.CompletableFuture.waitingGet(CompletableFuture.java:1729)
at java.util.concurrent.CompletableFuture.join(CompletableFuture.java:1934)
at
org.apache.ratis.server.impl.RaftServerImpl.appendEntries(RaftServerImpl.java:1379)
at
org.apache.ratis.server.impl.RaftServerProxy.appendEntries(RaftServerProxy.java:649)
at
org.apache.ratis.netty.server.NettyRpcService.handle(NettyRpcService.java:231)
at
org.apache.ratis.netty.server.NettyRpcService$InboundHandler.channelRead0(NettyRpcService.java:95)
at
org.apache.ratis.netty.server.NettyRpcService$InboundHandler.channelRead0(NettyRpcService.java:91)
at
org.apache.ratis.thirdparty.io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:99)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at
org.apache.ratis.thirdparty.io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at
org.apache.ratis.thirdparty.io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:346)
at
org.apache.ratis.thirdparty.io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:318)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:444)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:412)
at
org.apache.ratis.thirdparty.io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1410)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:440)
at
org.apache.ratis.thirdparty.io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:420)
at
org.apache.ratis.thirdparty.io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:919)
at
org.apache.ratis.thirdparty.io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:166)
at
org.apache.ratis.thirdparty.io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:788)
at
org.apache.ratis.thirdparty.io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:724)
at
org.apache.ratis.thirdparty.io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:650)
at
org.apache.ratis.thirdparty.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:562)
at
org.apache.ratis.thirdparty.io.netty.util.concurrent.SingleThreadEventExecutor$4.run(SingleThreadEventExecutor.java:997)
at
org.apache.ratis.thirdparty.io.netty.util.internal.ThreadExecutorMap$2.run(ThreadExecutorMap.java:74)
at
org.apache.ratis.thirdparty.io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
at java.lang.Thread.run(Thread.java:882)
*The debug logs which confirmed the cause:*
2024-06-23 11:44:08,881 [1@group-47BEDE733167-StateMachineUpdater] INFO
raftlog.RaftLog - 1@group-47BEDE733167-SegmentedRaftLog: snapshotIndex:
updateIncreasingly 17818160 -> 17868160
2024-06-23 11:44:08,881 [1@group-47BEDE733167-StateMachineUpdater] DEBUG
raftlog.RaftLog - purging segments:toTruncate: null
toDelete: [(17817216, 17818372) isOpen? false, length=0, newEndIndex=0,
(17818373, 17819224) isOpen? false, length=0, newEndIndex=0, (17819225,
17820474) isOpen? false, length=0, newEndIndex=0, (17820475, 17821368) isOpen?
false, length=0, newEndIndex=0, (17821369, 17822360) isOpen? false, length=0,
newEndIndex=0, (17822361, 17823347) isOpen? false, length=0, newEndIndex=0,
(17823348, 17824136) isOpen? false, length=0, newEndIndex=0, (17824137,
17825440) isOpen? false, length=0, newEndIndex=0, (17825441, 17826153) isOpen?
false, length=0, newEndIndex=0, (17826154, 17826936) isOpen? false, length=0,
newEndIndex=0, (17826937, 17827393) isOpen? false, length=0, newEndIndex=0,
(17827394, 17828569) isOpen? false, length=0, newEndIndex=0, (17828570,
17829095) isOpen? false, length=0, newEndIndex=0, (17829096, 17830279) isOpen?
false, length=0, newEndIndex=0, (17830280, 17831209) isOpen? false, length=0,
newEndIndex=0, (17831210, 17831887) isOpen? false, length=0, newEndIndex=0,
(17831888, 17832491) isOpen? false, length=0, newEndIndex=0, (17832492,
17833577) isOpen? false, length=0, newEndIndex=0, (17833578, 17834387) isOpen?
false, length=0, newEndIndex=0, (17834388, 17835369) isOpen? false, length=0,
newEndIndex=0, (17835370, 17836107) isOpen? false, length=0, newEndIndex=0,
(17836108, 17837307) isOpen? false, length=0, newEndIndex=0, (17837308,
17838140) isOpen? false, length=0, newEndIndex=0, (17838141, 17838591) isOpen?
false, length=0, newEndIndex=0, (17838592, 17839411) isOpen? false, length=0,
newEndIndex=0, (17839412, 17840613) isOpen? false, length=0, newEndIndex=0,
(17840614, 17841672) isOpen? false, length=0, newEndIndex=0, (17841673,
17842917) isOpen? false, length=0, newEndIndex=0, (17842918, 17843636) isOpen?
false, length=0, newEndIndex=0, (17843637, 17844560) isOpen? false, length=0,
newEndIndex=0, (17844561, 17847272) isOpen? false, length=0, newEndIndex=0,
(17847273, 17847746) isOpen? false, length=0, newEndIndex=0, (17847747,
17848169) isOpen? false, length=0, newEndIndex=0, (17848170, 17848631) isOpen?
false, length=0, newEndIndex=0, (17848632, 17849078) isOpen? false, length=0,
newEndIndex=0, (17849079, 17850026) isOpen? false, length=0, newEndIndex=0,
(17850027, 17850490) isOpen? false, length=0, newEndIndex=0, (17850491,
17851382) isOpen? false, length=0, newEndIndex=0, (17851383, 17852289) isOpen?
false, length=0, newEndIndex=0, (17852290, 17853645) isOpen? false, length=0,
newEndIndex=0, (17853646, 17854151) isOpen? false, length=0, newEndIndex=0,
(17854152, 17855586) isOpen? false, length=0, newEndIndex=0, (17855587,
17856772) isOpen? false, length=0, newEndIndex=0, (17856773, 17857571) isOpen?
false, length=0, newEndIndex=0, (17857572, 17858043) isOpen? false, length=0,
newEndIndex=0, (17858044, 17858598) isOpen? false, length=0, newEndIndex=0,
(17858599, 17859922) isOpen? false, length=0, newEndIndex=0, (17859923,
17860327) isOpen? false, length=0, newEndIndex=0, (17860328, 17861304) isOpen?
false, length=0, newEndIndex=0, (17861305, 17862381) isOpen? false, length=0,
newEndIndex=0, (17862382, 17863572) isOpen? false, length=0, newEndIndex=0,
(17863573, 17864018) isOpen? false, length=0, newEndIndex=0, (17864019,
17865114) isOpen? false, length=0, newEndIndex=0, (17865115, 17866739) isOpen?
false, length=0, newEndIndex=0, (17866740, 17867551) isOpen? false, length=0,
newEndIndex=0]
2024-06-23 11:44:08,881 [1@group-47BEDE733167-StateMachineUpdater] DEBUG
segmented.SegmentedRaftLogWorker - 1@group-47BEDE733167-SegmentedRaftLogWorker
adds IO task PurgeLog:17867551
2024-06-23 11:44:08,881 [1@group-47BEDE733167-StateMachineUpdater] DEBUG
segmented.SegmentedRaftLogWorker - added IO task (queueSize: 5)
PurgeLog:17867551
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
raftlog.RaftLog - complete future of IO task WriteLog:17876749
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - done IO task WriteLog:17876749
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - dequeued IO task (index: 0, queueSize: 4)
WriteLog:17876750
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - offer future of IO task WriteLog:17876750
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - done IO task WriteLog:17876750
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - dequeued IO task (index: 0, queueSize: 3)
WriteLog:17876751
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - offer future of IO task WriteLog:17876751
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - done IO task WriteLog:17876751
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - dequeued IO task (index: 0, queueSize: 2)
WriteLog:17876752
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - offer future of IO task WriteLog:17876752
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - done IO task WriteLog:17876752
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - dequeued IO task (index: 0, queueSize: 1)
WriteLog:17876753
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - offer future of IO task WriteLog:17876753
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - done IO task WriteLog:17876753
2024-06-23 11:44:08,881 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - dequeued IO task (index: 0, queueSize: 0)
PurgeLog:17867551
2024-06-23 11:44:08,904 [1@group-47BEDE733167-SegmentedRaftLogWorker] INFO
raftlog.RaftLog - 1@group-47BEDE733167-SegmentedRaftLog: purgeIndex:
updateToMax old=17817215, new=17867551, updated? true
2024-06-23 11:44:08,904 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
raftlog.RaftLog - complete future of IO task PurgeLog:17867551
2024-06-23 11:44:08,904 [1@group-47BEDE733167-SegmentedRaftLogWorker] DEBUG
segmented.SegmentedRaftLogWorker - done IO task PurgeLog:17867551
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