[
https://issues.apache.org/jira/browse/FLINK-22946?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17362905#comment-17362905
]
Piotr Nowojski commented on FLINK-22946:
----------------------------------------
Hi [~guokuai.huang], thanks for reporting this issue. I think indeed you are
right.
On the outputs there are multiple threads that simultaneously recycling the
buffers, but on the output side, there is no {{BufferManager}} to cause this
problem, right?
{quote}
1. Case by case solution. Note that input channel A (locked A) gave the
released network buffer to input channel B (waiting to lock B), and input
channel B (locked B) gave the released network buffer to input channel A
(waiting to lock A) ), so when an input channel releases the network buffer,
first check whether it is also waiting for the network buffer, and if it is,
directly allocate it to itself, which can avoid the situation that different
input channels exchange network buffers.
{quote}
I'm not sure if I understand this solution, as {{BufferManager}}s are already
checking in BufferManager.AvailableBufferQueue#addExclusiveBuffer:
{code:java}
if (getAvailableBufferSize() > numRequiredBuffers) {
{code}
Is it a problem that there is some lingering registered buffer availability
listener? Can you elaborate more about this idea of yours?
About the proposed solution #2. I think you are right, we could also recycle
the buffers outside of the {{bufferQueue}} lock in {{BufferManager#recycle}},
instead of inside {{BufferManager.AvailableBufferQueue#addExclusiveBuffer}} as
it is now?
> Network buffer deadlock introduced by unaligned checkpoint
> ----------------------------------------------------------
>
> Key: FLINK-22946
> URL: https://issues.apache.org/jira/browse/FLINK-22946
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Checkpointing
> Affects Versions: 1.13.0, 1.13.1
> Reporter: Guokuai Huang
> Priority: Blocker
> Labels: stale-blocker
> Attachments: Screen Shot 2021-06-09 at 6.39.47 PM.png, Screen Shot
> 2021-06-09 at 7.02.04 PM.png
>
>
> We recently encountered deadlock when using unaligned checkpoint. Below are
> two thread stacks that cause deadlock:
> {code:java}
> "Channel state writer Join(xxxxxx) (34/256)#1": at
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager.notifyBufferAvailable(BufferManager.java:296)
> - waiting to lock <0x00000007296dfa90> (a
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager$AvailableBufferQueue)
> at
> org.apache.flink.runtime.io.network.buffer.LocalBufferPool.fireBufferAvailableNotification(LocalBufferPool.java:507)
> at
> org.apache.flink.runtime.io.network.buffer.LocalBufferPool.recycle(LocalBufferPool.java:494)
> at
> org.apache.flink.runtime.io.network.buffer.LocalBufferPool.recycle(LocalBufferPool.java:460)
> at
> org.apache.flink.runtime.io.network.buffer.NetworkBuffer.deallocate(NetworkBuffer.java:182)
> at
> org.apache.flink.shaded.netty4.io.netty.buffer.AbstractReferenceCountedByteBuf.handleRelease(AbstractReferenceCountedByteBuf.java:110)
> at
> org.apache.flink.shaded.netty4.io.netty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:100)
> at
> org.apache.flink.runtime.io.network.buffer.NetworkBuffer.recycleBuffer(NetworkBuffer.java:156)
> at
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager$AvailableBufferQueue.addExclusiveBuffer(BufferManager.java:399)
> at
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager.recycle(BufferManager.java:200)
> - locked <0x00000007296bc450> (a
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager$AvailableBufferQueue)
> at
> org.apache.flink.runtime.io.network.buffer.NetworkBuffer.deallocate(NetworkBuffer.java:182)
> at
> org.apache.flink.shaded.netty4.io.netty.buffer.AbstractReferenceCountedByteBuf.handleRelease(AbstractReferenceCountedByteBuf.java:110)
> at
> org.apache.flink.shaded.netty4.io.netty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:100)
> at
> org.apache.flink.runtime.io.network.buffer.NetworkBuffer.recycleBuffer(NetworkBuffer.java:156)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateCheckpointWriter.write(ChannelStateCheckpointWriter.java:173)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateCheckpointWriter.writeInput(ChannelStateCheckpointWriter.java:131)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequest.lambda$write$0(ChannelStateWriteRequest.java:63)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequest$$Lambda$785/722492780.accept(Unknown
> Source) at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequest.lambda$buildWriteRequest$2(ChannelStateWriteRequest.java:93)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequest$$Lambda$786/1360749026.accept(Unknown
> Source) at
> org.apache.flink.runtime.checkpoint.channel.CheckpointInProgressRequest.execute(ChannelStateWriteRequest.java:212)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequestDispatcherImpl.dispatchInternal(ChannelStateWriteRequestDispatcherImpl.java:82)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequestDispatcherImpl.dispatch(ChannelStateWriteRequestDispatcherImpl.java:59)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequestExecutorImpl.loop(ChannelStateWriteRequestExecutorImpl.java:96)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequestExecutorImpl.run(ChannelStateWriteRequestExecutorImpl.java:75)
> at
> org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequestExecutorImpl$$Lambda$253/502209879.run(Unknown
> Source) at java.lang.Thread.run(Thread.java:745){code}
> {code:java}
> "Join(xxxxxx) (34/256)#1": at
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager.notifyBufferAvailable(BufferManager.java:296)
> - waiting to lock <0x00000007296bc450> (a
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager$AvailableBufferQueue)
> at
> org.apache.flink.runtime.io.network.buffer.LocalBufferPool.fireBufferAvailableNotification(LocalBufferPool.java:507)
> at
> org.apache.flink.runtime.io.network.buffer.LocalBufferPool.recycle(LocalBufferPool.java:494)
> at
> org.apache.flink.runtime.io.network.buffer.LocalBufferPool.recycle(LocalBufferPool.java:460)
> at
> org.apache.flink.runtime.io.network.buffer.NetworkBuffer.deallocate(NetworkBuffer.java:182)
> at
> org.apache.flink.shaded.netty4.io.netty.buffer.AbstractReferenceCountedByteBuf.handleRelease(AbstractReferenceCountedByteBuf.java:110)
> at
> org.apache.flink.shaded.netty4.io.netty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:100)
> at
> org.apache.flink.runtime.io.network.buffer.NetworkBuffer.recycleBuffer(NetworkBuffer.java:156)
> at
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager$AvailableBufferQueue.addExclusiveBuffer(BufferManager.java:399)
> at
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager.recycle(BufferManager.java:200)
> - locked <0x00000007296dfa90> (a
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager$AvailableBufferQueue)
> at
> org.apache.flink.runtime.io.network.buffer.NetworkBuffer.deallocate(NetworkBuffer.java:182)
> at
> org.apache.flink.shaded.netty4.io.netty.buffer.AbstractReferenceCountedByteBuf.handleRelease(AbstractReferenceCountedByteBuf.java:110)
> at
> org.apache.flink.shaded.netty4.io.netty.buffer.AbstractReferenceCountedByteBuf.release(AbstractReferenceCountedByteBuf.java:100)
> at
> org.apache.flink.runtime.io.network.buffer.NetworkBuffer.recycleBuffer(NetworkBuffer.java:156)
> at
> org.apache.flink.runtime.io.network.api.serialization.SpillingAdaptiveSpanningRecordDeserializer.getNextRecord(SpillingAdaptiveSpanningRecordDeserializer.java:95)
> at
> org.apache.flink.streaming.runtime.io.AbstractStreamTaskNetworkInput.emitNext(AbstractStreamTaskNetworkInput.java:95)
> at
> org.apache.flink.streaming.runtime.io.StreamOneInputProcessor.processInput(StreamOneInputProcessor.java:66)
> at
> org.apache.flink.streaming.runtime.io.StreamTwoInputProcessor.processInput(StreamTwoInputProcessor.java:96)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.processInput(StreamTask.java:423)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask$$Lambda$226/1801850008.runDefaultAction(Unknown
> Source) at
> org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.runMailboxLoop(MailboxProcessor.java:204)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.runMailboxLoop(StreamTask.java:681)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.executeInvoke(StreamTask.java:636)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask$$Lambda$577/1653738667.run(Unknown
> Source) at
> org.apache.flink.streaming.runtime.tasks.StreamTask.runWithCleanUpOnFail(StreamTask.java:647)
> at
> org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:620)
> at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:779) at
> org.apache.flink.runtime.taskmanager.Task.run(Task.java:566) at
> java.lang.Thread.run(Thread.java:745){code}
> The root cause of this problem is that unaligned checkpoint makes it possible
> that *under the same input gate,* *multiple input channels may recycle
> network buffer at the same time.*
> Previously, network buffer recycling would only occur serially between input
> channels under the same input gate, because each sub-task is process Input
> data serially, and an input gate belongs to only one sub-task. When unaligned
> checkpoint is enabled, each input channel will take a snapshot of the input
> channel when it receives the checkpoint barrier, and the network buffer may
> be recycled in the process.
> Unfortunately, *the current network buffer recycling mechanism does not take
> into account the situation where multiple input channels perform network
> buffer recycling at the same time.* The following code block is from
> org.apache.flink.runtime.io.network.partition.consumer.BufferManager$AvailableBufferQueue
> that causes deadlock when multiple input channels under same input gate
> perform network buffer recycling at the same time.
> !Screen Shot 2021-06-09 at 7.02.04 PM.png!
> The solution to this problem is quite straightforward. Here are two possible
> solutions:
> *1. Case by case solution.* Note that input channel A (locked A) gave the
> released network buffer to input channel B (waiting to lock B), and input
> channel B (locked B) gave the released network buffer to input channel A
> (waiting to lock A) ), so when an input channel releases the network buffer,
> first check whether it is also waiting for the network buffer, and if it is,
> directly allocate it to itself, which can avoid the situation that different
> input channels exchange network buffers.
> 2. *A straightforward solution.* Considering that the input channel occupies
> the lock during recycle to remove the network buffer from the bufferQueue,
> the subsequent operations do not need to hold this lock. Therefore, we only
> need to place Buffer::recycleBuffer outside the bufferQueue lock to avoid
> deadlock.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
