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mysqlctl: Improve handling of the lock file #15404

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merged 1 commit into from
Mar 7, 2024
Merged

mysqlctl: Improve handling of the lock file #15404

merged 1 commit into from
Mar 7, 2024

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dbussink
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@dbussink dbussink commented Mar 5, 2024

This handles the case where mysqlctld might get assigned the same pid and improves the logging for when this case happens.

Related Issue(s)

Part of addressing #14552

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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

@dbussink
mysqlctl: Improve handling of the lock file
ac45ddd 
This handles the case where mysqlctld might get assigned the same pid
and improves the logging for when this case happens.

Signed-off-by: Dirkjan Bussink <[email protected]>
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vitess-bot bot commented Mar 5, 2024

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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 Mar 5, 2024
@dbussink dbussink added Type: Bug Component: TabletManager 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 Mar 5, 2024
@github-actions github-actions bot added this to the v20.0.0 milestone Mar 5, 2024
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codecov bot commented Mar 5, 2024

Codecov Report

Attention: Patch coverage is 88.88889% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 65.66%. Comparing base (9cd8ffc) to head (ac45ddd).

Files Patch % Lines
go/vt/mysqlctl/mysqld.go 88.88% 1 Missing ⚠️
Additional details and impacted files 
@@           Coverage Diff           @@
##             main   #15404   +/-   ##
=======================================
  Coverage   65.65%   65.66%           
=======================================
  Files        1562     1562           
  Lines      193940   193948    +8     
=======================================
+ Hits       127328   127352   +24     
+ Misses      66612    66596   -16

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mattlord
mattlord approved these changes Mar 6, 2024
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go/vt/mysqlctl/mysqld.go
@@ -460,6 +460,10 @@ func cleanupLockfile(socket string, ts string) error {
log.Errorf("%v: error parsing pid from lock file: %v", ts, err)
return err
}
if os.Getpid() == p {
log.Infof("%v: lock file at %s is ours, removing it", ts, lockPath)
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I'd take the opportunity to rename ts as ts == *topo.Server in the code base. :-)

No idea why that was chosen for:

ts := fmt.Sprintf("Mysqld.Start(%v)", time.Now().Unix())

time start, I guess? Up to you if you want to change it.

go/vt/mysqlctl/mysqld.go
@@ -460,6 +460,10 @@ func cleanupLockfile(socket string, ts string) error {
log.Errorf("%v: error parsing pid from lock file: %v", ts, err)
return err
}
if os.Getpid() == p {
log.Infof("%v: lock file at %s is ours, removing it", ts, lockPath)
return os.Remove(lockPath)
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Do we really want to do this? I'm curious how this happens, where we have the same PID we had before? Or am I missing something. That being said, I suppose it's fine since eventually the PID will get reused and could be reused by another mysqld process. In that case though I'm also not sure what "ours" really means in that context.

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@mattlord It can happen inside containers. Each container is unique and gets new PIDs so it's possible there to have PID reusage much more often.

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Yes, when using persistent storage for the lock file that lives across containers. Makes sense. Thanks!

GuptaManan100
GuptaManan100 approved these changes Mar 7, 2024
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LGTM!

@dbussink dbussink merged commit 6c73053 into vitessio:main Mar 7, 2024
114 checks passed
@dbussink dbussink deleted the improve-mysqlctld-lock-file-handling branch March 7, 2024 08:31
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@mattlord mattlord mattlord approved these changes

@GuptaManan100 GuptaManan100 GuptaManan100 approved these changes

@deepthi deepthi Awaiting requested review from deepthi deepthi is a code owner

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