Limit max # of DB connections for mysql backend

Author: cschleiden

backend/mysql/mysql.go

@@ -49,6 +49,10 @@ func NewMysqlBackend(host string, port int, user, password, database string, opt
 		panic(err)
 	}
 
+	if options.MySQLOptions != nil {
+		options.MySQLOptions(db)
+	}
+
 	b := &mysqlBackend{
 		dsn:        dsn,
 		db:         db,

backend/mysql/options.go

@@ -1,12 +1,16 @@
 package mysql
 
 import (
+	"database/sql"
+
 	"github.com/cschleiden/go-workflows/backend"
 )
 
 type options struct {
 	backend.Options
 
+	MySQLOptions func(db *sql.DB)
+
 	// ApplyMigrations automatically applies database migrations on startup.
 	ApplyMigrations bool
 }
@@ -20,6 +24,12 @@ func WithApplyMigrations(applyMigrations bool) option {
 	}
 }
 
+func WithMySQLOptions(f func(db *sql.DB)) option {
+	return func(o *options) {
+		o.MySQLOptions = f
+	}
+}
+
 // WithBackendOptions allows to pass generic backend options.
 func WithBackendOptions(opts ...backend.BackendOption) option {
 	return func(o *options) {

bench/main.go

@@ -6,7 +6,6 @@ import (
 	"flag"
 	"fmt"
 	"log"
-	"log/slog"
 	"os"
 	"sync"
 	"time"
@@ -40,7 +39,10 @@ func main() {
 	defer cancel()
 
 	mm := newMemMetrics()
-	ba := getBackend(*b, backend.WithLogger(slog.New(&nullHandler{})), backend.WithMetrics(mm))
+	ba := getBackend(*b,
+		// backend.WithLogger(slog.New(&nullHandler{})),
+		backend.WithMetrics(mm),
+	)
 
 	wo := worker.DefaultWorkerOptions
 	wo.WorkflowExecutorCacheSize = *cacheSize
@@ -129,7 +131,12 @@ func getBackend(b string, opt ...backend.BackendOption) backend.Backend {
 			panic(err)
 		}
 
-		return monoprocess.NewMonoprocessBackend(mysql.NewMysqlBackend("localhost", 3306, "root", "root", "bench", mysql.WithBackendOptions(opt...)))
+		return monoprocess.NewMonoprocessBackend(
+			mysql.NewMysqlBackend("localhost", 3306, "root", "root", "bench", mysql.WithBackendOptions(opt...),
+				mysql.WithMySQLOptions(func(db *sql.DB) {
+					db.SetMaxOpenConns(100)
+				})),
+		)
 
 	case "redis":
 		rclient := redisv8.NewUniversalClient(&redisv8.UniversalOptions{