From 34e050daad57e56465cfc0289bcc45a5fa1a4469 Mon Sep 17 00:00:00 2001
From: Andre Medeiros <hello@andre.cool>
Date: Mon, 23 May 2022 18:51:30 -0400
Subject: [PATCH] tweak scheduler

---
 internal/cmd/scheduler.go | 27 ++++++++++++++++-----------
 1 file changed, 16 insertions(+), 11 deletions(-)

diff --git a/internal/cmd/scheduler.go b/internal/cmd/scheduler.go
index 8729857..408632a 100644
--- a/internal/cmd/scheduler.go
+++ b/internal/cmd/scheduler.go
@@ -21,7 +21,10 @@ import (
 	"github.com/christianselig/apollo-backend/internal/repository"
 )
 
-const batchSize = 250
+const (
+	batchSize             = 1000
+	maxNotificationChecks = 5000
+)
 
 func SchedulerCmd(ctx context.Context) *cobra.Command {
 	cmd := &cobra.Command{
@@ -383,7 +386,8 @@ func enqueueAccounts(ctx context.Context, logger *zap.Logger, statsd *statsd.Cli
 	now := time.Now()
 	next := now.Add(domain.NotificationCheckInterval)
 
-	ids := []int64{}
+	ids := make([]int64, maxNotificationChecks)
+	numids := 0
 	enqueued := 0
 	skipped := 0
 
@@ -395,7 +399,7 @@ func enqueueAccounts(ctx context.Context, logger *zap.Logger, statsd *statsd.Cli
 	}()
 
 	err := pool.BeginFunc(ctx, func(tx pgx.Tx) error {
-		stmt := `
+		stmt := fmt.Sprintf(`
 			UPDATE accounts
 			SET next_notification_check_at = $2
 			WHERE accounts.id IN(
@@ -404,18 +408,19 @@ func enqueueAccounts(ctx context.Context, logger *zap.Logger, statsd *statsd.Cli
 				WHERE next_notification_check_at < $1
 				ORDER BY next_notification_check_at
 				FOR UPDATE SKIP LOCKED
-				LIMIT 5000
+				LIMIT %d
 			)
-			RETURNING accounts.id`
+			RETURNING accounts.id`, maxNotificationChecks)
 		rows, err := tx.Query(ctx, stmt, now, next)
 		if err != nil {
 			return err
 		}
 		defer rows.Close()
-		for rows.Next() {
+		for i := 0; rows.Next(); i++ {
 			var id int64
 			_ = rows.Scan(&id)
-			ids = append(ids, id)
+			ids[i] = id
+			numids = i
 		}
 		return nil
 	})
@@ -425,17 +430,17 @@ func enqueueAccounts(ctx context.Context, logger *zap.Logger, statsd *statsd.Cli
 		return
 	}
 
-	if len(ids) == 0 {
+	if numids == 0 {
 		return
 	}
 
 	logger.Debug("enqueueing account batch", zap.Int("count", len(ids)), zap.Time("start", now))
 
 	// Split ids in batches
-	for i := 0; i < len(ids); i += batchSize {
+	for i := 0; i < numids; i += batchSize {
 		j := i + batchSize
-		if j > len(ids) {
-			j = len(ids)
+		if j > numids {
+			j = numids
 		}
 		batch := Int64Slice(ids[i:j])