Re: [PR] CASSANDRA-19576 Write compaction history asynchronously through a bounded executor [cassandra]

["cheeeee (via GitHub)" <gi...@apache.org>]

cheeeee commented on PR #5141:
URL: https://github.com/apache/cassandra/pull/5141#issuecomment-5643468187

   Withdrawing this patch.
   
   It does remove the stall: with the memtable pool exhausted and flush blocked, an unpatched
   compaction thread parks in MemtableAllocator.allocate inside the compaction_history write and the
   compaction does not finish in 45 s, while with the patch it completes in about 200 ms.
   
   But deferring the write to a dedicated thread does not remove the dependency, it moves it: that
   thread blocks on the same pool, so under the pressure the ticket describes the history is still not
   written. On top of that the patch makes drain wait up to cassandra.drain_executor_timeout_ms and
   then fail if the writer is parked, and turns a write failure into a log-only event.
   
   Compaction is a path that frees resources, and its last step allocates from the pool it is trying to
   relieve. A fix that holds up needs the diagnostic record to be independent of that pool, which is a
   design decision for the owners of this area rather than something to land as a bug fix. I will put
   the reproduction, the stack and the trade-offs in CASSANDRA-19576 so the analysis is not lost.


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