[GitHub] davisp commented on issue #1772: Slow operation in couch_proc_manager

[GitBox <gi...@apache.org>]

davisp commented on issue #1772: Slow operation in couch_proc_manager
URL: https://github.com/apache/couchdb/issues/1772#issuecomment-442537845
 
 
   Also a bit more background I realize I didn't share. We had a couple nodes (not even entire clusters) that experienced a backup on the couch_proc_manager process to the tune of 6M+ message in the mailbox. What likely happened was that when the node was booted there was a sudden massive surge of view indexing triggered. The slightly slower couch_proc_manager was then not able to keep up processing the new process requests which leads to a positive feedback cycle. Lots of processes trying to use get_proc piling into the message queue, and the larger that message queue gets the slower couch_proc_manager gets because its garbage collecting a lot due to that new loop over the `os:getenv()` output with the string creations and so on.
   
   Its fairly similar to how couch_server can get stuck with the same issues. The big mailbox causes garbage collection to dominate the CPU time of that process preventing it from being able to catch up and clear out its mailbox.

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