From 0accbde48bd7927365e2a153c3edd970d1175ab7 Mon Sep 17 00:00:00 2001
From: Andre Medeiros <hello@andre.cool>
Date: Sat, 20 May 2023 09:47:38 -0400
Subject: [PATCH] use a locking mechanism for the scheduler instead of the
 singleton model in the cron lib

---
 internal/cmd/scheduler.go | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/internal/cmd/scheduler.go b/internal/cmd/scheduler.go
index de66a75..1296257 100644
--- a/internal/cmd/scheduler.go
+++ b/internal/cmd/scheduler.go
@@ -23,8 +23,14 @@ import (
 	"github.com/christianselig/apollo-backend/internal/repository"
 )
 
-const batchSize = 250
-const accountEnqueueSeconds = 60
+const (
+	batchSize             = 250
+	accountEnqueueSeconds = 60
+)
+
+var (
+	enqueueAccountsMutex sync.Mutex
+)
 
 func SchedulerCmd(ctx context.Context) *cobra.Command {
 	cmd := &cobra.Command{
@@ -103,9 +109,7 @@ func SchedulerCmd(ctx context.Context) *cobra.Command {
 			s := gocron.NewScheduler(time.UTC)
 			s.SetMaxConcurrentJobs(8, gocron.WaitMode)
 
-			eaj, _ := s.Every(5).Seconds().Do(func() { enqueueAccounts(ctx, logger, statsd, db, redis, luaSha, notifQueue) })
-			eaj.SingletonMode()
-
+			_, _ = s.Every(5).Seconds().Do(func() { enqueueAccounts(ctx, logger, statsd, db, redis, luaSha, notifQueue) })
 			_, _ = s.Every(5).Seconds().Do(func() { enqueueSubreddits(ctx, logger, statsd, db, []rmq.Queue{subredditQueue, trendingQueue}) })
 			_, _ = s.Every(5).Seconds().Do(func() { enqueueUsers(ctx, logger, statsd, db, userQueue) })
 			_, _ = s.Every(5).Seconds().Do(func() { enqueueLiveActivities(ctx, logger, db, redis, luaSha, liveActivitiesQueue) })
@@ -456,6 +460,12 @@ func enqueueStuckAccounts(ctx context.Context, logger *zap.Logger, statsd *stats
 }
 
 func enqueueAccounts(ctx context.Context, logger *zap.Logger, statsd *statsd.Client, pool *pgxpool.Pool, redisConn *redis.Client, luaSha string, queue rmq.Queue) {
+	if enqueueAccountsMutex.TryLock() {
+		defer enqueueAccountsMutex.Unlock()
+	} else {
+		return
+	}
+
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()