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Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

Since topic deletion cannot always be performed immediately (due to offline replicas, partitions are being reassigned, etc), the Controller marks a topic for deletion and enqueues it for later processing. When a large number of topics /(partitions, really) are deleted at once, the Controlled can get quite backed up and start affecting other parts of the system. Since topic deletes are asynchronous, it is difficult to know when the Controller has worked through the queue of topics marked for deletion. Currentlyit can take significant time for the Controller to process everything. During this time, it is not unusual for the Controller to get bogged down. During these times, it would be useful to know how many topics still remain to be deleted. Currently, the only way to check on the progress is by looking directly in ZooKeeper at the /admin/delete_topics znode. In a production environment this is rather cumbersome and is somewhat dangerous ill-advised (poking around in ZK for on a running Kafka cluster). 

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