[GitHub] [incubator-superset] betodealmeida opened a new pull request #8594: Create new session for tab migration

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

betodealmeida opened a new pull request #8594: Create new session for tab migration
URL: https://github.com/apache/incubator-superset/pull/8594
 
 
   ### CATEGORY
   
   Choose one
   
   - [X] Bug Fix
   - [ ] Enhancement (new features, refinement)
   - [ ] Refactor
   - [ ] Add tests
   - [ ] Build / Development Environment
   - [ ] Documentation
   
   ### SUMMARY
   <!--- Describe the change below, including rationale and design decisions -->
   
   Friday we turned on the `SQLLAB_BACKEND_PERSISTENCE` at Lyft, and noticed a deadlock when migrating SQL Lab tabs from `localStorage` to the backend:
   
   ```
   sqlalchemy.exc.OperationalError: (_mysql_exceptions.OperationalError) (1213, 'Deadlock found when trying to get lock; try restarting transaction')
   [SQL: INSERT INTO tab_state (created_on, changed_on, extra_json, user_id, label, active, database_id, `schema`, `sql`, query_limit, latest_query_id, autorun, template_params, created_by_fk, changed_by_fk) VALUES (%s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s, %s)]
   [parameters: (datetime.datetime(2019, 11, 16, 1, 39, 45, 903405), datetime.datetime(2019, 11, 16, 1, 39, 45, 903410), '{}', '1963', 'dim_applicants', 1, 7, None, 'select * from events_annotated.event_ride_requested limit 10', None, None, 0, None, 1963, 1963)]
   ```
   
   Note that there was no data loss, and the tabs were migrated successfully on a refresh.
   
   I tried to repro this locally, migrating 20 tabs to a MySQL database, but I wasn't able to hit the deadlock. Looking at the code, it seems that we reuse the same session across all requests, so I refactored it to create a new session for each request.
   
   @mistercrunch do you think this would fix the problem? I'm not super familiar with SQL Alchemy, but from what I read this should work.
   
   <!-- ### BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF -->
   <!--- Skip this if not applicable -->
   
   ### TEST PLAN
   <!--- What steps should be taken to verify the changes -->
   
   I wasn't able to repro the original bug, but ran this code to ensure that it still works.
   
   ### 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
   
   ### REVIEWERS
   
   @mistercrunch 

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