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Posted to notifications@couchdb.apache.org by GitBox <gi...@apache.org> on 2020/01/25 01:58:40 UTC
[GitHub] [couchdb] wohali opened a new pull request #2487: Revert default
priority change for couch_server
wohali opened a new pull request #2487: Revert default priority change for couch_server
URL: https://github.com/apache/couchdb/pull/2487
## Overview
In a59540132 we introduced a default increase in process priority for `couch_server` to high.
While tracking down #2437 , I managed to git bisect the problem to this commit.
This lead me to this thread on erlang-questions:
http://erlang.org/pipermail/erlang-questions/2018-June/095677.html
Notably:
> a single high-priority process in a tight loop stops all other processes, including those of max priority.
This problem surfaces on Erlang 21 and 22 specifically - and is exactly what we're seeing.
While we could do a specific version check, I think it would be healthier for now to disable this specific optimization by default, and only re-enable once we can track down what's going on in 21/22 that is causing scheduler collapse in this fashion.
## Testing recommendations
`while true; do make eunit apps=mem3; done` should run for hours without a hang. Most commonly the hang occurs in the reshard tests (during which various `couchjs` processes are spawned.)
## Related Issues or Pull Requests
Closes #2437 and may help with #2423 - needs more testing.
## Checklist
- [X] Code is written and works correctly
- [X] Changes are covered by tests
- [X] Any new configurable parameters are documented in `rel/overlay/etc/default.ini`
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[GitHub] [couchdb] wohali commented on issue #2487: Revert default priority
change for couch_server
Posted by GitBox <gi...@apache.org>.
wohali commented on issue #2487: Revert default priority change for couch_server
URL: https://github.com/apache/couchdb/pull/2487#issuecomment-578380637
6 hours later, a595401 is still hung but b02599e is not. I'll let it run overnight but I think this is it.
Thanks for the +1!
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[GitHub] [couchdb] wohali merged pull request #2487: Revert default priority
change for couch_server
Posted by GitBox <gi...@apache.org>.
wohali merged pull request #2487: Revert default priority change for couch_server
URL: https://github.com/apache/couchdb/pull/2487
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