From 90bc665a2169b1abc2bdf11db3c4df98360fef34 Mon Sep 17 00:00:00 2001
From: Yevgeniy Miretskiy <yevgeniy@cockroachlabs.com>
Date: Fri, 8 Sep 2023 10:06:36 -0400
Subject: [PATCH] changefeedccl: Fix data race in lagging spans metric

Fix a race bug in lagging spans metric.

Fixes: #110235

Release note: None
---
 pkg/ccl/changefeedccl/changefeed_test.go |  2 ++
 pkg/ccl/changefeedccl/metrics.go         | 11 ++++++++---
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/pkg/ccl/changefeedccl/changefeed_test.go b/pkg/ccl/changefeedccl/changefeed_test.go
index f486987c1400..bed759932ede 100644
--- a/pkg/ccl/changefeedccl/changefeed_test.go
+++ b/pkg/ccl/changefeedccl/changefeed_test.go
@@ -1736,6 +1736,8 @@ func TestNoBackfillAfterNonTargetColumnDrop(t *testing.T) {
 
 func TestChangefeedColumnDropsWithFamilyAndNonFamilyTargets(t *testing.T) {
 	defer leaktest.AfterTest(t)()
+	defer log.Scope(t).Close(t)
+
 	testFn := func(t *testing.T, s TestServer, f cdctest.TestFeedFactory) {
 		sqlDB := sqlutils.MakeSQLRunner(s.DB)
 
diff --git a/pkg/ccl/changefeedccl/metrics.go b/pkg/ccl/changefeedccl/metrics.go
index a2676eaeb2a6..789b27ae63f0 100644
--- a/pkg/ccl/changefeedccl/metrics.go
+++ b/pkg/ccl/changefeedccl/metrics.go
@@ -804,10 +804,15 @@ func (s *sliMetrics) getLaggingRangesCallback() func(int64) {
 	// If 3 ranges catch up, last=10,i=7: X.Dec(10 - 7) = X.Dec(3)
 	// If 4 ranges fall behind, last=7,i=11: X.Dec(7 - 11) = X.Inc(4)
 	// If 1 lagging range is deleted, last=7,i=10: X.Dec(11-10) = X.Dec(1)
-	var last int64
+	last := struct {
+		syncutil.Mutex
+		v int64
+	}{}
 	return func(i int64) {
-		s.LaggingRanges.Dec(last - i)
-		last = i
+		last.Lock()
+		defer last.Unlock()
+		s.LaggingRanges.Dec(last.v - i)
+		last.v = i
 	}
 }