pingcap / pingcap/tiflash

Task might leak in corner cases

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affects-6.1 affects-6.2 component/compute severity/minor type/bug
Dominant language
C++
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Description

Bug Report

Please answer these questions before submitting your issue. Thanks!
It's detected when we enable random_tunnel_init_rpc_failure_failpoint. The whole story is like:

  1. When Tiflash servers receive MPPTasks, they first do some preparation work and then register to TaskManager. And if TiDB's cancelMPPTask request came before thre registering, the task won't be cancelled. The task still have chances to fail itself if tunnel/receiver can pass the error message.
  2. Since init_rpc failpoint will fail task very quickly, so it happened to reproduce such cases.
1. Minimal reproduce step (Required)
2. What did you expect to see? (Required)
3. What did you see instead (Required)
4. What is your TiFlash version? (Required)

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the issue with the random_tunnel_init_rpc_failure_failpoint and trace the cancellation path when TiDB's cancelMPPTask request arrives before TaskManager registration. Done means an MPPTask is cancelled reliably in that ordering rather than surviving until a tunnel or receiver reports an error.

Written by the indexing model from the issue text.

Assessment

Tech stack
cpp
Domain
distributed-systems
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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