fix indexing startup for devcontainer.

[juanmrad]

Summary

Fixes #1507

This PR adds a check on the app config to ensure we do not run background tasks when we are just running the DB migrations. That way we do not have race conditions where we are expecting DB to have data when the data is still not migrated.

Test Plan

Tested locally by cleaning up my DB and started the containers again having TASK_INDEX_CACHE set to true and did not see any errors. while it failed when I reverted my change and cleaned up my db.

I tried to add a CI check for ensuring no model changes are uncommitted with:

  check-pending-migrations:
    name: Check Pending Migrations
    runs-on: ubuntu-latest
    # Service containers to run with `tests`
    services:
      postgres:
        image: postgres
        # Provide the env variables
        env:
          POSTGRES_DB: media_match_test
          POSTGRES_USER: media_match
          POSTGRES_PASSWORD: hunter2
        ports:
          - 5432:5432
        # Set health checks to wait until postgres has started
        options: >-
          --health-cmd pg_isready
          --health-interval 10s
          --health-timeout 5s
          --health-retries 5
    steps:
      - uses: actions/checkout@v2
      - name: Build docker image
        run: docker build -t local .
      - name: Test with pytest on docker image
        run: |
          docker run --network="host" local sh -c "python -m pip install --upgrade pip ;
            pip install -e '.[test]' ;
            MIGRATION_COMMAND=1 flask --app OpenMediaMatch.app db check --directory /workspace/src/OpenMediaMatch/migrations"

But this may need more work, and be best for a separate PR.

[Dcallies]

This environment variable solution looks like it might work, but I wonder if we want to generalize it even more and only start apscheduler when the run command has been triggered.

I think triggering these during app creation and not during pre-serve/pre-fork might have been a design mistake.

[Dcallies]

If you fixed it, remove the comment :P

[Dcallies]

non-blocking question: As an alternative, can we detect whether the "Run" command has been triggered, and only startup apscheduler then?

[Dcallies]

Guess I was wrong :P

[Dcallies]

What do you know, it was typed correctly :P