Metadata doesn't have a session on startup when processing amqp

Support
#1

Hey all,

In my Cuba application I have a rabbitMQ Listener which listens to a rabbitMQ queue. When picking up a message from the queue, I convert that message to an object using the injected Metadata interface, with the method metadata.getClass(“project$Order”), and then I serialize it.

All works fine, but when I deploy a new version, on starting up, the first few messages it picks up from the queue fail due a NullPointerException.That’s because the Metadata interface doesn’t have it’s session yet, so it fails on the above method.

What would be the proper way of handling this ?

[edit] I’ve found these in the logfiles. The second line is my attempt to get the session, which normally throws the exception:

  • 12:58:35.402 INFO com.haulmont.cuba.core.sys.MetadataImpl - Initializing metadata
  • Failed attempt # 1 getting metadata.getSession()
  • 12:58:35.675 INFO com.haulmont.cuba.core.sys.MetadataImpl - Metadata initialized in 273ms

Thanks,

Jeroen

#3

Hi Jeroen,

You should defer the event processing until the platform beans are fully initialized.

Ideally you should start the processing only after receiving AppContextStartedEvent with the order greater than Events.LOWEST_PLATFORM_PRECEDENCE.

If it’s impossible, you can try to wait until Metadata session is initialized by checking metadata.getSession() != null in a loop. However, this approach may not work until you get the platform update including this fix: More reliable Metadata session initialization · Issue #811 · cuba-platform/cuba · GitHub

1 Like
#5

I resolved it with the second option for now, Ill dive into the first option.

Thanks Konstatin!