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AliveFetcherThreadCount: this basically exposes the size of the internal thread map in AbstractFetcherManager.
dead-log-cleaner-thread-count: this would expose the size number of the configured threads - size of the ArrayBuffer that maintains the CleanerThread instances in LogCleaner. This can show the actual live count of the threads.
log-cleaner-current-live-thread-rate: this is a variation of the above. We can divide the alive thread count with the cleaner thread configuration to get a rate which would be more suitable to use as a base for alerts. 

Proposed Changes

There would be no changes beside the changes listed in the previous section.

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