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https://issues.apache.org/jira/browse/FLINK-13100?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16881003#comment-16881003
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zhijiang commented on FLINK-13100:
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[~pnowojski] the previous deadlock was ever happened on our side and we fixed
it internally in Alibaba. Considering the new BoundedBlockingSubpartition only
focusing on mmap way at the first version, so we were not caring about this
issue then. Now the 32-bit system could touch the way of file-file, then it is
very easy to trigger this problem now when the flush is pending as I described
above.
> Fix the unexpected IOException during FileBufferReader#nextBuffer
> -----------------------------------------------------------------
>
> Key: FLINK-13100
> URL: https://issues.apache.org/jira/browse/FLINK-13100
> Project: Flink
> Issue Type: Sub-task
> Components: Runtime / Network
> Reporter: zhijiang
> Priority: Blocker
>
> In the implementation of FileBufferReader#nextBuffer, we expect the next
> memory segment always available based on the assumption that the nextBuffer
> call could only happen when the previous buffer was recycled before.
> Otherwise it would throw an IOException in current implementation.
> In fact, the above assumption is not making sense based on the credit-based
> and zero-copy features in network. The detail processes are as follows:
> * The netty thread finishes calling the channel.writeAndFlush() in
> PartitionRequestQueue and adds a listener to handle the ChannelFuture later.
> Before future done, the corresponding buffer is not recycled because of
> zero-copy improvement.
> * Before the previous future done, the netty thread could trigger next
> writeAndFlush via processing addCredit message, then
> FileBufferReader#nextBuffer would throw exception because of previous buffer
> not recycled.
> We thought of several ways for solving this potential bug:
> * It does not trigger the next writeAndFlush before the previous future
> done. To do so it has to maintain the future state and check it in relevant
> actions. I wonder it might bring performance regression in network throughput
> and bring extra state management.
> * Adjust the implementation of current FileBufferReader. We ever regarded
> the blocking partition view as always available based on the next buffer read
> ahead, so it would be always added into available queue in
> PartitionRequestQueue. Actually this next buffer ahead only simplifies the
> process of BoundedBlockingSubpartitionReader#notifyDataAvailable. The view
> availability could be judged based on available buffers in FileBufferReader
> instead of next buffer ahead. When the buffer is recycled into
> FileBufferReader after writeAndFlush done, it could call notifyDataAvailable
> to add this view into available queue in PartitionRequestQueue.
> I prefer the second way because it would not bring any bad impacts.
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