We have the following problem in production.

[ISS.0098.0064D] Publishing delayed while outbound store is draining. Service: wm.server.publish:publish
[ISS.0098.0062D] DefaultInboundBrokerDocDispatcher encountered Exception: java.lang.NullPointerException

What does java.lang.NullPointerException exception mean? Did the broker receive null document to publish?

Currently no documents are getting published. Can we restart the broker? How do we solve this problem?

As per my understanding, if broker server is re-started, it should automatically drain out the documents that
are in queue.

Did any body face the above issue? Your advise is greatly appreciated.

The IS Dispatcher is responsible for moving documents to and from the broker in other words the broker doesn’t connect to the IS server, the IS server connects to the broker.

THe message your are getting is generally found when connection to the broker is lost for some reason and the IS Dispatcher starts persisting documents locally (outbound store) until the Broker connection is re-established. Since the dispatcher is going to maintain the order of publishable documents and sequence, the outbound store is drained first before other documents are allowed to go to broker.

Sounds like you have more documents than the size of your outbound store is allowing. You need to find out why your IS Server is not talking to your broker. Do you see error messages in the server log about polling for broker connection?

Yes, I am also seeing the following messages in the server log around the same time:

[LGU.0002.0001E] Error getting broker log length: The request timed out.
[ISS.0098.0041C] Unable to connect to Broker. Starting to poll

Do you know, what could be the reason for loosing the IS - Broker connection?

Must likely culprit is your network connection but there could other reasons as well. Hard to know without some more details. You should monitor both environments when this condition occurs, looking at network, servers, OS’s etc. Is your broker up and running when this occurs? Is your broker reachable when this happens? What other things are going on when it happens? Certain time of day? Large number of transactions?