Tachyon Oracle

Feature or enhancement

Proposal:

The big question is: how we can ensure that Tachyon is trustworthy?

In particular: the profiler reports some frames, effectively: some distribution of gathered samples. How do we know if they actually match reality? How well do they match reality?

Do we even report the distribution of samples that's similar to how the actual app behaves? Do we report impossible frames?

These are not theoretical questions, as demonstrated by #151426, #151613 or #151022.

Especially in the non-blocking mode we don't have fully atomic reads. If we use too many remote calls, traverse the frames, coro or task-waiters in an inefficient way, or invalidate the cache incorrectly - there's a room for introducing the noise (bias? drift? whatever the name).

Unfortunately, the CI is not the right tool for the job, given that we should avoid flaky tests at all costs and the statistical nature of Tachyon means that we cannot aim for 100% perfection. Even in the blocking mode, we simply cannot guarantee that we block the target ideally.

With the pipeline of changes happening the Tachyon, I think we should introduce some "harness" for this purpose.

This was discussed offline with @pablogsal

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-153806

先檢視 issues #151426、#151613 和 #151022 中的 Tachyon 上下文，接著檢查連結的工作 gh-153806。提案沒有指定檔案、測試或進入點；完成表示定義一個 harness，用來評估回報的樣本分佈和影格是否符合觀察到的應用程式行為，包括 non-blocking-mode 雜訊。