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Prevent adding to query details after unserve common has started #15684

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@GuptaManan100 GuptaManan100 commented Apr 9, 2024

Description

This PR fixes the bug found in #15685. The problem was that we were adding to the queryDetails even after unserveCommon had been called and after the kill had happened. This is troublesome and has been fixed by preventing addition to the query details right after unserveCommon starts.

The fix entails adding a new state in the QueryList which stores the state of a cluster-wide action. The three values for the new state are -

  1. ClusterActionNotInProgress - This is the default state of a query list and the state that it starts in. This state signifies that no ClusterAction is in progress.
  2. ClusterActionInProgress - This state signifies a cluster action is ongoing, but the query list is still free to accept any new queries.
  3. ClusterActionNoQueries - This state signifies that a cluster action is ongoing and the query list should reject all new incoming queries.

The transitions between the 3 states are as follows -

flowchart LR
    NP[ClusterActionNotInProgress]
    IP[ClusterActionInProgress]
    NQ[ClusterActionNoQueries]
    NP -- Start execution of `unserveCommon` --> IP
    IP -- Finish execution of `unserveCommon` --> NP
    NQ -- Finish execution of `unserveCommon` --> NP
    IP -- Shutdown grace period expired --> NQ
Loading

The interesting thing to note here is that if we are in the ClusterActionNotInProgress state, then we ignore a transition to ClusterActionNoQueries. This is needed because sometimes the grace period might expire after the execution of unserveCommon has finished due to the fast path of not having any outstanding requests. In this case, we don't want the query list to stop accepting requests since no cluster action is in progress.

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  • "Backport to:" labels have been added if this change should be back-ported to release branches
  • If this change is to be back-ported to previous releases, a justification is included in the PR description
  • Tests were added or are not required
  • Did the new or modified tests pass consistently locally and on CI?
  • Documentation was added or is not required

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vitess-bot bot commented Apr 9, 2024

Review Checklist

Hello reviewers! 👋 Please follow this checklist when reviewing this Pull Request.

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@vitess-bot vitess-bot bot added NeedsBackportReason If backport labels have been applied to a PR, a justification is required NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsIssue A linked issue is missing for this Pull Request NeedsWebsiteDocsUpdate What it says labels Apr 9, 2024
@GuptaManan100 GuptaManan100 added Type: Bug Component: Cluster management Component: Query Serving and removed NeedsDescriptionUpdate The description is not clear or comprehensive enough, and needs work NeedsWebsiteDocsUpdate What it says NeedsIssue A linked issue is missing for this Pull Request NeedsBackportReason If backport labels have been applied to a PR, a justification is required labels Apr 9, 2024
@github-actions github-actions bot added this to the v20.0.0 milestone Apr 9, 2024
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codecov bot commented Apr 9, 2024

Codecov Report

Attention: Patch coverage is 86.66667% with 4 lines in your changes are missing coverage. Please review.

Project coverage is 68.40%. Comparing base (4a1870a) to head (880c5e3).
Report is 18 commits behind head on main.

Files Patch % Lines
go/vt/vttablet/tabletserver/query_executor.go 66.66% 4 Missing ⚠️
Additional details and impacted files
@@            Coverage Diff             @@
##             main   #15684      +/-   ##
==========================================
+ Coverage   68.13%   68.40%   +0.26%     
==========================================
  Files        1556     1556              
  Lines      195028   195136     +108     
==========================================
+ Hits       132888   133476     +588     
+ Misses      62140    61660     -480     

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@GuptaManan100 GuptaManan100 marked this pull request as ready for review April 9, 2024 10:46
… not deterministic anymore

Signed-off-by: Manan Gupta <[email protected]>
@GuptaManan100 GuptaManan100 requested a review from frouioui as a code owner April 9, 2024 10:49
go/vt/vttablet/tabletserver/livequeryz_test.go Outdated Show resolved Hide resolved
…fter the defer function has run

Signed-off-by: Manan Gupta <[email protected]>
@GuptaManan100 GuptaManan100 merged commit 9e40015 into vitessio:main Apr 11, 2024
101 checks passed
@GuptaManan100 GuptaManan100 deleted the prevent-addition-to-query-detail branch April 11, 2024 12:54
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