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https://issues.apache.org/jira/browse/DIRMINA-845?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13267479#comment-13267479
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Luigi Bitonti commented on DIRMINA-845:
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Hi Ilya,
Interesting report. would you be able to share some details of your solution?
Thanks,
Luigi
> ProtocolEncoderOutputImpl isn't thread-safe
> -------------------------------------------
>
> Key: DIRMINA-845
> URL: https://issues.apache.org/jira/browse/DIRMINA-845
> Project: MINA
> Issue Type: Bug
> Components: Filter
> Affects Versions: 2.0.4
> Reporter: Ilya Ivanov
>
> ProtocolEncoderOutputImpl uses ConcurrentLinkedQueue and at first look it
> seems to be thread-safe. But really concurrent execution of flush method
> isn't thread-safe (and write-mergeAll also).
> E.g. in RTMP several channels multiplexed in single connection. According
> protocol specification it's possible to write to different channels
> concurrently. But it doesn't work with MINA.
> I've synchronized channel writing, but it doesn't prevent concurrent run of
> flushing (in 2.0.4 it's done directly in ProtocolCodecFilter.filterWrite, but
> ProtocolEncoderOutputImpl.flush has the same problem).
> Here the fragment of flushing code:
> while (!bufferQueue.isEmpty()) {
> Object encodedMessage = bufferQueue.poll();
>
> if (encodedMessage == null) {
> break;
> }
> // Flush only when the buffer has remaining.
> if (!(encodedMessage instanceof IoBuffer) || ((IoBuffer)
> encodedMessage).hasRemaining()) {
> SocketAddress destination = writeRequest.getDestination();
> WriteRequest encodedWriteRequest = new
> EncodedWriteRequest(encodedMessage, null, destination);
> nextFilter.filterWrite(session, encodedWriteRequest);
> }
> }
> Suppose original packets sequence is A, B, ...
> Concurrent run of flushing may proceed as following:
> thread-1: Object encodedMessage = bufferQueue.poll(); // gets A packet
> thread-2: Object encodedMessage = bufferQueue.poll(); // gets B packet
> ...
> thread-2: nextFilter.filterWrite(...); // writes B packet
> thread-1: nextFilter.filterWrite(...); // writes A packet
> so, resulting sequence will B, A
> It's quite confusing result especially when documentation doesn't contain any
> explanation about such behavior.
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