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[v17] Fix SemaphoreLock context.Context implementation #52105

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merged 2 commits into from
Feb 13, 2025
Merged

[v17] Fix SemaphoreLock context.Context implementation #52105

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d1dc8a5
Fix SemaphoreLock context.Context implementation
GavinFrazar Feb 12, 2025
149df81
Merge branch 'branch/v17' into bot/backport-52046-branch/v17
GavinFrazar Feb 13, 2025
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47 changes: 10 additions & 37 deletions lib/services/semaphore.go
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Original file line number Diff line number Diff line change
Expand Up @@ -100,11 +100,11 @@ func (l *SemaphoreLockConfig) CheckAndSetDefaults() error {
// defer cancel()
// ... do work with newCtx ...
type SemaphoreLock struct {
// ctx is the parent context for the lease keepalive operation.
// Context is the parent context for the lease keepalive operation.
// it's used to propagate deadline cancellations from the parent
// context and to carry values for the context interface.
ctx context.Context
cancelCtx context.CancelFunc
context.Context
cancelCtx context.CancelCauseFunc
cfg SemaphoreLockConfig
lease0 types.SemaphoreLease
retry retryutils.Retry
Expand All @@ -128,31 +128,6 @@ func (l *SemaphoreLock) finish(err error) {
l.cond.Broadcast()
}

// Done signals that lease keepalive operations
// have stopped.
// If the parent context is canceled, the lease
// will be released and done will be closed.
func (l *SemaphoreLock) Done() <-chan struct{} {
return l.ctx.Done()
}

// Deadline returns the deadline of the parent context if it exists.
func (l *SemaphoreLock) Deadline() (time.Time, bool) {
return l.ctx.Deadline()
}

// Value returns the value associated with the key in the parent context.
func (l *SemaphoreLock) Value(key interface{}) interface{} {
return l.ctx.Value(key)
}

// Error returns the final error value.
func (l *SemaphoreLock) Err() error {
l.cond.L.Lock()
defer l.cond.L.Unlock()
return l.err
}

// Wait blocks until the final result is available. Note that
// this method may block longer than desired since cancellation of
// the parent context triggers the *start* of the release operation.
Expand All @@ -169,7 +144,7 @@ func (l *SemaphoreLock) Wait() error {
func (l *SemaphoreLock) Stop() {
l.closeOnce.Do(func() {
l.ticker.Stop()
l.cancelCtx()
l.cancelCtx(nil)
})
}

Expand All @@ -179,12 +154,12 @@ func (l *SemaphoreLock) Renewed() <-chan struct{} {
return l.renewalC
}

func (l *SemaphoreLock) keepAlive(ctx context.Context) {
func (l *SemaphoreLock) keepAlive() {
var nodrop bool
var err error
lease := l.lease0
defer func() {
l.cancelCtx()
l.cancelCtx(err)
l.Stop()
defer l.finish(err)
if nodrop {
Expand All @@ -210,7 +185,7 @@ Outer:
for {
select {
case tick := <-l.ticker.Chan():
leaseContext, leaseCancel := context.WithDeadline(ctx, lease.Expires)
leaseContext, leaseCancel := context.WithDeadline(l.Context, lease.Expires)
nextLease := lease
nextLease.Expires = tick.Add(l.cfg.Expiry)
for {
Expand Down Expand Up @@ -253,8 +228,6 @@ Outer:
return
}
}
case <-ctx.Done():
return
case <-l.Done():
return
}
Expand Down Expand Up @@ -308,9 +281,9 @@ func AcquireSemaphoreLock(ctx context.Context, cfg SemaphoreLockConfig) (*Semaph
if err != nil {
return nil, trace.Wrap(err)
}
ctx, cancel := context.WithCancel(ctx)
ctx, cancel := context.WithCancelCause(ctx)
lock := &SemaphoreLock{
ctx: ctx,
Context: ctx,
cancelCtx: cancel,
cfg: cfg,
lease0: *lease,
Expand All @@ -319,7 +292,7 @@ func AcquireSemaphoreLock(ctx context.Context, cfg SemaphoreLockConfig) (*Semaph
renewalC: make(chan struct{}),
cond: sync.NewCond(&sync.Mutex{}),
}
go lock.keepAlive(ctx)
go lock.keepAlive()
return lock, nil
}

Expand Down
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