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https://issues.apache.org/jira/browse/KAFKA-6529?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16357626#comment-16357626
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Ismael Juma commented on KAFKA-6529:
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[~damianguy] Yes, I think the PR should be merged today or tomorrow.
[~rsivaram] and [~hachikuji] are on it.
> Broker leaks memory and file descriptors after sudden client disconnects
> ------------------------------------------------------------------------
>
> Key: KAFKA-6529
> URL: https://issues.apache.org/jira/browse/KAFKA-6529
> Project: Kafka
> Issue Type: Bug
> Components: network
> Affects Versions: 1.0.0, 0.11.0.2
> Reporter: Graham Campbell
> Priority: Major
> Fix For: 1.1.0, 0.11.0.3, 1.0.2
>
>
> If a producer forcefully disconnects from a broker while it has staged
> receives, that connection enters a limbo state where it is no longer
> processed by the SocketServer.Processor, leaking the file descriptor for the
> socket and the memory used for the staged recieve queue for that connection.
> We noticed this during an upgrade from 0.9.0.2 to 0.11.0.2. Immediately after
> the rolling restart to upgrade, open file descriptors on the brokers started
> climbing uncontrollably. In a few cases brokers reached our configured max
> open files limit of 100k and crashed before we rolled back.
> We tracked this down to a buildup of muted connections in the
> Selector.closingChannels list. If a client disconnects from the broker with
> multiple pending produce requests, when the broker attempts to send an ack to
> the client it recieves an IOException because the TCP socket has been closed.
> This triggers the Selector to close the channel, but because it still has
> pending requests, it adds it to Selector.closingChannels to process those
> requests. However, because that exception was triggered by trying to send a
> response, the SocketServer.Processor has marked the channel as muted and will
> no longer process it at all.
> *Reproduced by:*
> Starting a Kafka broker/cluster
> Client produces several messages and then disconnects abruptly (eg.
> _./rdkafka_performance -P -x 100 -b broker:9092 -t test_topic_)
> Broker then leaks file descriptor previously used for TCP socket and memory
> for unprocessed messages
> *Proposed solution (which we've implemented internally)*
> Whenever an exception is encountered when writing to a socket in
> Selector.pollSelectionKeys(...) record that that connection failed a send by
> adding the KafkaChannel ID to Selector.failedSends. Then re-raise the
> exception to still trigger the socket disconnection logic. Since every
> exception raised in this function triggers a disconnect, we also treat any
> exception while writing to the socket as a failed send.
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