From 6c6137f9f2aef15ab9216bb3aa3eb2bdc71e32cf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C3=89mile=20R=C3=A9?= <emile@getprobo.com>
Date: Wed, 13 May 2026 11:18:05 +0400
Subject: [PATCH] Fix deadlock when updating tracker pattern last_matched_at
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Replace per-row UPDATE inside the detected-tracker loop with a single
bulk UPDATE ... WHERE id = ANY(...) after the loop. The old approach
locked pattern rows in request-dependent order, causing deadlocks
under concurrent ReportDetectedTrackers calls.

Signed-off-by: Émile Ré <emile@getprobo.com>
---
 pkg/cookiebanner/service.go     | 17 ++++++++++-----
 pkg/coredata/tracker_pattern.go | 38 +++++++++++++++++++++++++++++++++
 2 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/pkg/cookiebanner/service.go b/pkg/cookiebanner/service.go
index d4c1a7cf1..0cd779e20 100644
--- a/pkg/cookiebanner/service.go
+++ b/pkg/cookiebanner/service.go
@@ -2023,6 +2023,7 @@ func (s *Service) ReportDetectedTrackers(
 
 			inserted := 0
 			now := time.Now()
+			var matchedPatternIDs []gid.GID
 
 			for _, dc := range req.Cookies {
 				if err := s.reportDetectedTracker(
@@ -2040,6 +2041,7 @@ func (s *Service) ReportDetectedTrackers(
 						InitiatorURL:  dc.InitiatorURL,
 					},
 					&inserted,
+					&matchedPatternIDs,
 				); err != nil {
 					return err
 				}
@@ -2060,6 +2062,7 @@ func (s *Service) ReportDetectedTrackers(
 						InitiatorURL: ds.InitiatorURL,
 					},
 					&inserted,
+					&matchedPatternIDs,
 				); err != nil {
 					return err
 				}
@@ -2083,6 +2086,13 @@ func (s *Service) ReportDetectedTrackers(
 				}
 			}
 
+			if len(matchedPatternIDs) > 0 {
+				var patterns coredata.TrackerPatterns
+				if err := patterns.UpdateLastMatchedAt(ctx, tx, scope, matchedPatternIDs, now); err != nil {
+					return fmt.Errorf("cannot update tracker pattern last_matched_at: %w", err)
+				}
+			}
+
 			if inserted > 0 {
 				if err := banner.SetPatternAnalysisRequested(ctx, tx); err != nil {
 					return fmt.Errorf("cannot request pattern analysis: %w", err)
@@ -2112,6 +2122,7 @@ func (s *Service) reportDetectedTracker(
 	now time.Time,
 	info detectedTrackerInfo,
 	inserted *int,
+	matchedPatternIDs *[]gid.GID,
 ) error {
 	var matchedPattern coredata.TrackerPattern
 	err := matchedPattern.FindMatchingPattern(ctx, tx, scope, banner.ID, info.TrackerType, info.Identifier)
@@ -2126,11 +2137,7 @@ func (s *Service) reportDetectedTracker(
 	var patternID *gid.GID
 	if err == nil {
 		patternID = &matchedPattern.ID
-		matchedPattern.LastMatchedAt = &now
-		matchedPattern.UpdatedAt = now
-		if updateErr := matchedPattern.Update(ctx, tx, scope); updateErr != nil {
-			return fmt.Errorf("cannot update tracker pattern last_matched_at: %w", updateErr)
-		}
+		*matchedPatternIDs = append(*matchedPatternIDs, matchedPattern.ID)
 	} else {
 		newPattern := &coredata.TrackerPattern{
 			ID:               gid.New(scope.GetTenantID(), coredata.TrackerPatternEntityType),
diff --git a/pkg/coredata/tracker_pattern.go b/pkg/coredata/tracker_pattern.go
index 4667c8ad4..c1662eb40 100644
--- a/pkg/coredata/tracker_pattern.go
+++ b/pkg/coredata/tracker_pattern.go
@@ -801,6 +801,44 @@ WHERE
 	return count, nil
 }
 
+func (tps *TrackerPatterns) UpdateLastMatchedAt(
+	ctx context.Context,
+	tx pg.Tx,
+	scope Scoper,
+	patternIDs []gid.GID,
+	matchedAt time.Time,
+) error {
+	if len(patternIDs) == 0 {
+		return nil
+	}
+
+	q := `
+UPDATE tracker_patterns
+SET
+	last_matched_at = @matched_at,
+	updated_at = @updated_at
+WHERE
+	%s
+	AND id = ANY(@pattern_ids)
+`
+
+	q = fmt.Sprintf(q, scope.SQLFragment())
+
+	args := pgx.StrictNamedArgs{
+		"pattern_ids": patternIDs,
+		"matched_at":  matchedAt,
+		"updated_at":  matchedAt,
+	}
+	maps.Copy(args, scope.SQLArguments())
+
+	_, err := tx.Exec(ctx, q, args)
+	if err != nil {
+		return fmt.Errorf("cannot update last_matched_at for tracker patterns: %w", err)
+	}
+
+	return nil
+}
+
 func (tps *TrackerPatterns) MoveToCategoryByCookieCategoryID(
 	ctx context.Context,
 	tx pg.Tx,