From 28c24931b63ebbbd37ead827b26d440457328d27 Mon Sep 17 00:00:00 2001
From: Hector Sanjuan <code@hector.link>
Date: Mon, 20 Jun 2022 22:03:03 +0200
Subject: [PATCH] pintracker: fix some races resulting in wrong metric counts

I believe this fixes the issue with some metrics like pinning going into
negative numbers occasionally. Fixes #1702.
---
 pintracker/optracker/operation.go        | 14 +++++++----
 pintracker/optracker/operationtracker.go | 30 +++++++++++++++++-------
 2 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/pintracker/optracker/operation.go b/pintracker/optracker/operation.go
index 50224d04..5a0d5322 100644
--- a/pintracker/optracker/operation.go
+++ b/pintracker/optracker/operation.go
@@ -75,7 +75,7 @@ func newOperation(ctx context.Context, pin api.Pin, typ OperationType, ph Phase,
 	defer span.End()
 
 	ctx, cancel := context.WithCancel(ctx)
-	return &Operation{
+	op := &Operation{
 		ctx:    ctx,
 		cancel: cancel,
 
@@ -89,6 +89,8 @@ func newOperation(ctx context.Context, pin api.Pin, typ OperationType, ph Phase,
 		ts:           time.Now(),
 		error:        "",
 	}
+	tracker.recordMetricUnsafe(op, 1)
+	return op
 }
 
 // String returns a string representation of an Operation.
@@ -124,6 +126,7 @@ func (op *Operation) Context() context.Context {
 func (op *Operation) Cancel() {
 	_, span := trace.StartSpan(op.ctx, "optracker/Cancel")
 	op.cancel()
+	op.tracker.recordMetric(op, -1)
 	span.End()
 }
 
@@ -141,14 +144,15 @@ func (op *Operation) Phase() Phase {
 // SetPhase changes the Phase and updates the timestamp.
 func (op *Operation) SetPhase(ph Phase) {
 	_, span := trace.StartSpan(op.ctx, "optracker/SetPhase")
-	op.tracker.recordMetric(op, -1)
 	op.mu.Lock()
 	{
+		op.tracker.recordMetricUnsafe(op, -1)
 		op.phase = ph
 		op.ts = time.Now()
+		op.tracker.recordMetricUnsafe(op, 1)
 	}
 	op.mu.Unlock()
-	op.tracker.recordMetric(op, 1)
+
 	span.End()
 }
 
@@ -200,15 +204,15 @@ func (op *Operation) Error() string {
 // an error message. It updates the timestamp.
 func (op *Operation) SetError(err error) {
 	_, span := trace.StartSpan(op.ctx, "optracker/SetError")
-	op.tracker.recordMetric(op, -1)
 	op.mu.Lock()
 	{
+		op.tracker.recordMetricUnsafe(op, -1)
 		op.phase = PhaseError
 		op.error = err.Error()
 		op.ts = time.Now()
+		op.tracker.recordMetricUnsafe(op, 1)
 	}
 	op.mu.Unlock()
-	op.tracker.recordMetric(op, 1)
 	span.End()
 }
 
diff --git a/pintracker/optracker/operationtracker.go b/pintracker/optracker/operationtracker.go
index ffca373c..663d32a5 100644
--- a/pintracker/optracker/operationtracker.go
+++ b/pintracker/optracker/operationtracker.go
@@ -83,11 +83,14 @@ func (opt *OperationTracker) TrackNewOperation(ctx context.Context, pin api.Pin,
 	defer opt.mu.Unlock()
 
 	op, ok := opt.operations[pin.Cid]
-	if ok { // operation exists
+	if ok { // operation exists for the CID
 		if op.Type() == typ && op.Phase() != PhaseError && op.Phase() != PhaseDone {
-			return nil // an ongoing operation of the same sign exists
+			// an ongoing operation of the same
+			// type. i.e. pinning, or queued.
+			return nil
 		}
-		opt.recordMetric(op, -1)
+		// i.e. operations in error phase
+		// i.e. pin operations that need to be canceled for unpinning
 		op.Cancel() // cancel ongoing operation and replace it
 	}
 
@@ -99,7 +102,6 @@ func (opt *OperationTracker) TrackNewOperation(ctx context.Context, pin api.Pin,
 	}
 	logger.Debugf("'%s' on cid '%s' has been created with phase '%s'", typ, pin.Cid, ph)
 	opt.operations[pin.Cid] = op2
-	opt.recordMetric(op2, 1)
 	return op2
 }
 
@@ -355,12 +357,13 @@ func initializeMetrics(ctx context.Context) {
 	stats.Record(ctx, observations.PinsPinning.M(0))
 }
 
-func (opt *OperationTracker) recordMetric(op *Operation, val int64) {
-	if opt == nil {
+func (opt *OperationTracker) recordMetricUnsafe(op *Operation, val int64) {
+	if opt == nil || op == nil {
 		return
 	}
-	if op.Type() == OperationPin {
-		switch op.Phase() {
+
+	if op.opType == OperationPin {
+		switch op.phase {
 		case PhaseError:
 			pinErrors := atomic.AddInt64(&opt.pinErrorCount, val)
 			stats.Record(op.Context(), observations.PinsPinError.M(pinErrors))
@@ -376,6 +379,17 @@ func (opt *OperationTracker) recordMetric(op *Operation, val int64) {
 	}
 }
 
+func (opt *OperationTracker) recordMetric(op *Operation, val int64) {
+	if op == nil {
+		return
+	}
+	op.mu.RLock()
+	{
+		opt.recordMetricUnsafe(op, val)
+	}
+	op.mu.RUnlock()
+}
+
 // PinQueueSize returns the current number of items queued to pin.
 func (opt *OperationTracker) PinQueueSize() int64 {
 	return atomic.LoadInt64(&opt.pinQueuedCount)