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Prevent permanent worker deadlock when cutover times out waiting for binlog sentinel #1637

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Merged
meiji163 merged 8 commits into from
Apr 29, 2026
Merged

Prevent permanent worker deadlock when cutover times out waiting for binlog sentinel #1637

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ff567e2
Prevent permanent worker deadlock when cutover times out waiting for …
VarunChandola Mar 4, 2026
83a6830
Merge branch 'master' into varun/fix-alleventsuptolockprocessed-deadlock
meiji163 Mar 9, 2026
17a6d5a
Merge branch 'master' into varun/fix-alleventsuptolockprocessed-deadlock
meiji163 Mar 18, 2026
9bf9d5e
Merge branch 'master' into varun/fix-alleventsuptolockprocessed-deadlock
meiji163 Apr 8, 2026
298d0ee
Merge branch 'master' into varun/fix-alleventsuptolockprocessed-deadlock
meiji163 Apr 8, 2026
7d1825d
Merge branch 'master' into varun/fix-alleventsuptolockprocessed-deadlock
meiji163 Apr 23, 2026
24c2cc3
gofmt & make comment succinct
meiji163 Apr 29, 2026
55d483d
Merge branch 'master' into varun/fix-alleventsuptolockprocessed-deadlock
meiji163 Apr 29, 2026
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18 changes: 10 additions & 8 deletions go/logic/migrator.go
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Original file line number Diff line number Diff line change
Expand Up @@ -104,14 +104,16 @@ type Migrator struct {

func NewMigrator(context *base.MigrationContext, appVersion string) *Migrator {
migrator := &Migrator{
appVersion: appVersion,
hooksExecutor: NewHooksExecutor(context),
migrationContext: context,
parser: sql.NewAlterTableParser(),
ghostTableMigrated: make(chan bool),
firstThrottlingCollected: make(chan bool, 3),
rowCopyComplete: make(chan error),
allEventsUpToLockProcessed: make(chan *lockProcessedStruct),
appVersion: appVersion,
hooksExecutor: NewHooksExecutor(context),
migrationContext: context,
parser: sql.NewAlterTableParser(),
ghostTableMigrated: make(chan bool),
firstThrottlingCollected: make(chan bool, 3),
rowCopyComplete: make(chan error),
// Buffered to MaxRetries() to prevent a deadlock when waitForEventsUpToLock times out.
// (see https://github.com/github/gh-ost/pull/1637)
allEventsUpToLockProcessed: make(chan *lockProcessedStruct, context.MaxRetries()),
Comment on lines +114 to +116
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Copilot AI Apr 29, 2026

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make(chan *lockProcessedStruct, context.MaxRetries()) won’t compile because the channel buffer size parameter must be of type int, but MigrationContext.MaxRetries() returns int64 (go/base/context.go:495). Convert to int (and consider guarding against overflow if you want to be extra defensive).

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Comment on lines +114 to +116
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Copilot AI Apr 29, 2026

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This change is meant to prevent a specific deadlock scenario, but there’s no regression test exercising the “timeout then applier executes stale sentinel” behavior. Consider adding a unit test that constructs a Migrator, performs a non-blocking send on allEventsUpToLockProcessed without any receiver, and/or asserts the channel has the expected buffering based on MaxRetries() so future refactors don’t reintroduce the unbuffered-channel deadlock.

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copyRowsQueue: make(chan tableWriteFunc),
applyEventsQueue: make(chan *applyEventStruct, base.MaxEventsBatchSize),
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