[
https://issues.apache.org/jira/browse/KAFKA-6415?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Dong Lin resolved KAFKA-6415.
-----------------------------
Resolution: Fixed
> KafkaLog4jAppender deadlocks when logging from producer network thread
> ----------------------------------------------------------------------
>
> Key: KAFKA-6415
> URL: https://issues.apache.org/jira/browse/KAFKA-6415
> Project: Kafka
> Issue Type: Bug
> Components: log
> Reporter: Rajini Sivaram
> Assignee: Rajini Sivaram
> Priority: Major
> Fix For: 2.1.0
>
>
> When a log entry is appended to a Kafka topic using KafkaLog4jAppender, the
> producer.send operation may block waiting for metadata. This can result in
> deadlocks in a couple of scenarios if a log entry from the producer network
> thread is also at a log level that results in the entry being appended to a
> Kafka topic.
> 1. Producer's network thread will attempt to send data to a Kafka topic and
> this is unsafe since producer.send may block waiting for metadata, causing a
> deadlock since the thread will not process the metadata request/response.
> 2. KafkaLog4jAppender#append is invoked while holding the lock of the logger.
> So the thread waiting for metadata in the initial send will be holding the
> logger lock. If the producer network thread has.a log entry that needs to be
> appended, it will attempt to acquire the logger lock and deadlock.
> This was probably the case right from the beginning when KafkaLog4jAppender
> was introduced, but did not cause any issues so far since there were only
> debug log entries in that path which were not logged to a Kafka topic by any
> of the tests. A recent info level log entry introduced by the commit
> https://github.com/apache/kafka/commit/a3aea3cf4dbedb293f2d7859e0298bebc8e2185f
> is causing system test failures in log4j_appender_test.py due to the
> deadlock.
> The asynchronous append case can be fixed by moving all send operations to a
> separate thread. But KafkaLog4jAppender also has a syncSend option which
> blocks append while holding the logger lock until the send completes. Not
> sure how this can be fixed if we want to support log appends from the
> producer network thread.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
