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Posted to commits@pulsar.apache.org by GitBox <gi...@apache.org> on 2019/10/16 01:24:02 UTC
[GitHub] [pulsar] rdhabalia opened a new pull request #5391: [pulsar-broker]
Fix: race condition : Failed to read-more entries on dispatcher
rdhabalia opened a new pull request #5391: [pulsar-broker] Fix: race condition : Failed to read-more entries on dispatcher
URL: https://github.com/apache/pulsar/pull/5391
### Motivation
Due to race condition on `messagesToRedeliver`, dispatcher tries to access `delayedDeliveryTracker` which is empty and it is getting below exception so, dispatcher is not able to read entries.
```
22:05:03.693 [pulsar-io-22-7] WARN io.netty.util.concurrent.AbstractEventExecutor - A task raised an exception. Task: org.apache.pulsar.broker.service.persisten
t.PersistentDispatcherMultipleConsumers$$Lambda$965/0x0000000800912840@cdfd37a
java.util.NoSuchElementException: No value present
at java.util.Optional.get(Optional.java:148) ~[?:?]
at org.apache.pulsar.broker.service.persistent.PersistentDispatcherMultipleConsumers.getMessagesToReplayNow(PersistentDispatcherMultipleConsumers.java:728) ~[pulsar-broker-2.4.3-yahoo.jar:2.4.3-yahoo]
at org.apache.pulsar.broker.service.persistent.PersistentDispatcherMultipleConsumers.readMoreEntries(PersistentDispatcherMultipleConsumers.java:298) ~[pulsar-broker-2.4.3-yahoo.jar:2.4.3-yahoo]
at org.apache.pulsar.broker.service.persistent.PersistentDispatcherMultipleConsumers.lambda$addUnAckedMessages$374(PersistentDispatcherMultipleConsumers.java:646) ~[pulsar-broker-2.4.3-yahoo.jar:2.4.3-yahoo]
at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java:163) [netty-all-4.1.32.Final.jar:4.1.32.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:404) [netty-all-4.1.32.Final.jar:4.1.32.Final]
at io.netty.channel.epoll.EpollEventLoop.run(EpollEventLoop.java:335) [netty-all-4.1.32.Final.jar:4.1.32.Final]
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:909) [netty-all-4.1.32.Final.jar:4.1.32.Final]
at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30) [netty-all-4.1.32.Final.jar:4.1.32.Final]
at java.lang.Thread.run(Thread.java:834) [?:?]
```
With this fix, dispatcher will atomically fetches replay-messages without accessing `delayedDeliveryTracker`.
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