fix idle in transaction

It happend all the time, that connections were hanging in idle in
transaction state.
This was caused by a rollback stuck behind a sleep loop to wait for the
next bunch of checks to run.

This also replaces a Query() call with QueryRow, as we only expect a
single row and this cleans up the code a bit.

1 files changed, 8 insertions, 18 deletions

diff --git a/cmd/moncheck/main.go b/cmd/moncheck/main.go
index 3080309..7253c07 100644
--- a/cmd/moncheck/main.go
+++ b/cmd/moncheck/main.go
@@ -87,7 +87,7 @@ func check(thread int, db *sql.DB, waitDuration, timeout time.Duration, hostname
 			log.Printf("[%d] could not start transaction: %s", thread, err)
 			continue
 		}
-		rows, err := tx.Query(`select check_id, cmdLine, states, mapping_id
+		row := tx.QueryRow(`select check_id, cmdLine, states, mapping_id
 		from active_checks
 		where next_time < now()
 			and enabled
@@ -106,25 +106,15 @@ func check(thread int, db *sql.DB, waitDuration, timeout time.Duration, hostname
 			mapId   int
 			state   int
 		)
-		found := false
-		for rows.Next() {
-			if err := rows.Err(); err != nil {
-				log.Printf("could not fetch row: %s", err)
-				tx.Rollback()
-				break
-			}
-			err := rows.Scan(&id, pq.Array(&cmdLine), &states, &mapId)
-			if err != nil {
-				log.Printf("could not scan values: %s", err)
-				tx.Rollback()
-				break
-			}
-			found = true
-		}
-		if !found {
-			time.Sleep(waitDuration)
+		err = row.Scan(&id, pq.Array(&cmdLine), &states, &mapId)
+		if err != nil && err == sql.ErrNoRows {
 			tx.Rollback()
+			time.Sleep(waitDuration)
 			continue
+		} else if err != nil {
+			log.Printf("could not scan values: %s", err)
+			tx.Rollback()
+			break
 		}
 		ctx, cancel := context.WithTimeout(context.Background(), timeout)
 		cmd := exec.CommandContext(ctx, cmdLine[0], cmdLine[1:]...)