Prevent being blocked if no connection is available in the pool

Author: niksajakovljevic

util/lock.go

@@ -7,6 +7,11 @@ import (
 	"github.com/timescale/prometheus-postgresql-adapter/log"
 	"strconv"
 	"sync"
+	"time"
+)
+
+const (
+	waitForConnectionTimeout = time.Second
 )
 
 // PgAdvisoryLock is implementation of leader election based on PostgreSQL advisory locks. All adapters withing a HA group are trying
@@ -35,7 +40,8 @@ func getConn(pool *sql.DB, cur, maxRetries int) (*sql.Conn, error) {
 	if maxRetries == cur {
 		return nil, fmt.Errorf("max attempts reached. giving up on getting a db connection")
 	}
-	lockConn, err := pool.Conn(context.Background())
+	ctx, _ := context.WithTimeout(context.Background(), waitForConnectionTimeout)
+	lockConn, err := pool.Conn(ctx)
 	if err != nil {
 		return nil, fmt.Errorf("error getting DB connection: %v", err)
 	}