Zhen Zhang created HELIX-548:
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Summary: race condition in Helix message handler factory
registration
Key: HELIX-548
URL: https://issues.apache.org/jira/browse/HELIX-548
Project: Apache Helix
Issue Type: Bug
Reporter: Zhen Zhang
-- copied from email --
I have a small issue when running a Helix cluster in Docker (all on the same
machine, very small RTT):
I register two message handler factories, similarly to the way it is done in
BootstrapProcess.java example. The manager is not yet connected. My
understanding is that this places the handlers in a hashmap from which they
will be read and registered later, upon connect.
Upon connect, I see that the DefaultMessagingService.onConnected function is
called and Helix starts registering the message handlers. However, messages
start arriving already and HelixTaskExecutor.createMessageHandler is called,
before all handlers have been registered. The result is that I get
NullPointerExceptions for the missing handlers in the following line of
HelixTaskExecutor.createMessageHandler:
MessageHandlerFactory handlerFactory = item.factory();
due to the fact that there is no item (MessageHandlerFactoryRegistryItem) for
that message type registered yet.
I came upon this bug after updating the git code from an old snapshot of 0.7.1.
I saw that the relevant code changes are from around the summer.
Regards,
Vlad
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