syncer: do not try to handle jobs anymore if the context is done (#1295)

syncer/syncer.go

@@ -1018,6 +1018,18 @@ func (s *Syncer) sync(tctx *tcontext.Context, queueBucket string, db *DBConn, jo
 		if len(jobs) == 0 {
 			return 0, nil
 		}
+
+		select {
+		case <-tctx.Ctx.Done():
+			// do not execute queries anymore, because they should be failed with a done context.
+			// and avoid some errors like:
+			//  - `driver: bad connection` for `BEGIN`
+			//  - `sql: connection is already closed` for `BEGIN`
+			tctx.L().Info("skip some remaining DML jobs in the job chan because the context is done", zap.Int("count", len(jobs)))
+			return 0, tctx.Ctx.Err() // return the error to trigger `fatalF`.
+		default:
+		}
+
 		queries := make([]string, 0, len(jobs))
 		args := make([][]interface{}, 0, len(jobs))
 		for _, j := range jobs {

tests/incremental_mode/run.sh

@@ -115,6 +115,9 @@ function run() {
     # meeting an error of context cancel.
     # when below check pass, it means we filter out that error, or that error doesn't happen.
     # we only focus on fails, to find any unfiltered context cancel error.
+    # and should not contain errors like:
+    #   - `driver: bad connection`
+    #   - `sql: connection is already closed`
     run_dm_ctl $WORK_DIR "127.0.0.1:$MASTER_PORT" \
         "pause-task test" \
         "\"result\": true" 3