Metadata request from DefaultEventHandler.handle repeats same topic over and over

It looks like we are calling BrokerPartitionInfo.updateInfo() with a list of the same topic repeated many times:

Here is the line:
Utils.swallowError(brokerPartitionInfo.updateInfo(outstandingProduceRequests.map(_.getTopic)))

The outstandingProduceRequests can (and generally would) have many entries for the same topic.

For example if I use the producer performance test with the default batch size on a topic "test" my metadata request will have the topic "test" repeated 200 times. On the server side we do several zk reads for each of these repetitions.

This is causing the metadata api to timeout in my perf test periodically.

I think the fix is simply to de-duplicate prior to the call (and perhaps again on the server in case of a misbehaving client).