john-bodley opened a new pull request #10280:
URL: https://github.com/apache/incubator-superset/pull/10280


   ### SUMMARY
   
   At Airbnb we had an incident with Celery where tasks weren't being picked up 
and the CPU was pegged at close to 100%. We configure Celery with the `gevent` 
pool and the only workaround to remedy the problem was to restart the workers 
sans `gevent`. 
   
   We haven't been able to track down the root cause of the problem, though a 
Google search surfaced a similar issue ( 
[celery/celery/issues#4999](https://github.com/celery/celery/issues/4999)) 
which I believe was fixed in `4.4.2` (which is the version Superset currently 
uses). The issue seems to be that there are no [release 
note](https://docs.celeryproject.org/en/latest/changelog.html) associated with 
said release nor does that tag exist within the Celery GitHub repo. Given there 
have been a number of recent releases (which mostly look like bug fixes) I felt 
it was prudent that we bumped the version of Celery to the latest stable 
version.
   
   Note we use a MySQL database for Superset and historically have been using 
the `mysqlclient` DBAPI but we're looking into using `PyMySQL` which fully 
supports `gevent`. We're not sure if this was the issue, but the Celery workers 
poll certain async engines, i.e., Presto, every few seconds per task and thus 
having a fully `gevent` compliant DBAPI may also be benefical.
   
   ### BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF
   <!--- Skip this if not applicable -->
   
   ### TEST PLAN
   
   CI.
   
   ### ADDITIONAL INFORMATION
   <!--- Check any relevant boxes with "x" -->
   <!--- HINT: Include "Fixes #nnn" if you are fixing an existing issue -->
   - [ ] Has associated issue:
   - [ ] Changes UI
   - [ ] Requires DB Migration.
   - [ ] Confirm DB Migration upgrade and downgrade tested.
   - [ ] Introduces new feature or API
   - [ ] Removes existing feature or API
   


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