Cache foundational flow catalog item per request

Wanderson Policarporequested to merge
wanpol/foundational-flow-catalog-item-nil-memoization into master

What does this MR do and why?

Duo Code Review through the Duo Agent Platform can fail with a 403 when it posts its comments, until the instance is restarted. This happens on self-managed instances where the foundational flows are seeded after GitLab has started (for example, when the flows are enabled for the first time). Retries help only when they reach a different Puma worker, so the success rate looks random.

The cause is that each Puma worker keeps the foundational flow catalog item it looked up first, for its whole life. A worker that looked up the Code Review flow before it was seeded keeps "not found", so the DAP Code Review check fails in that worker. With this change, the lookup is cached for one request only, so a newly seeded (or re-seeded) item is used on the next request.

The specs had their own workarounds for the stale cache. They are no longer necessary, so this MR removes them.

References

How to set up and validate locally

Use a GDK with the Duo Agent Platform set up, and the Code Review flow enabled for gitlab-duo/test.

  1. Make the Code Review flow catalog item temporarily invisible to the lookup. In a Rails console:

    item = Ai::Catalog::Item.with_foundational_flow_reference('code_review/v1').first
item.update_column(:foundational_flow_reference, 'code_review/v1-hidden')

  2. Open an MR in gitlab-duo/test and reload the page a few times, so that each Puma worker looks up the item while it is missing.

  3. Put the item back, which acts like the flow being seeded after GitLab started:

    item.update_column(:foundational_flow_reference, 'code_review/v1')

  4. On the MR, assign Duo as a reviewer and wait for the review to finish.

    • On master: Duo does not post the review comments. log/api_json.log shows POST /api/v4/ai/duo_workflows/code_review/add_comments with status 403 until you run gdk restart rails-web.
    • On this branch: Duo posts the review comments without a restart.

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