add more debugging

Signed-off-by: Mohamed Hamza <mhamza@fastmail.com>

Author: mhamza15

go/test/endtoend/backup/vtctlbackup/backup_utils.go

@@ -1009,6 +1009,30 @@ func verifyInitialReplication(t *testing.T) {
 			row.AsString("Last_IO_Error", ""),
 			row.AsString("Last_SQL_Error", ""),
 		)
+		if ioRunning != "Yes" || sqlRunning != "Yes" {
+			workerStatus, werr := replica1.VttabletProcess.QueryTablet(
+				"select worker_id, service_state, last_error_number, last_error_message from performance_schema.replication_applier_status_by_worker where last_error_number <> 0",
+				"",
+				true,
+			)
+			if werr != nil {
+				lastStatus = fmt.Sprintf("%s Worker_Status_Error=%v", lastStatus, werr)
+				return false
+			}
+			if workerStatus != nil && len(workerStatus.Rows) > 0 {
+				var workerErrors []string
+				for _, workerRow := range workerStatus.Named().Rows {
+					workerErrors = append(workerErrors, fmt.Sprintf(
+						"worker_id=%s service_state=%s last_error_number=%s last_error_message=%s",
+						workerRow.AsString("worker_id", ""),
+						workerRow.AsString("service_state", ""),
+						workerRow.AsString("last_error_number", ""),
+						workerRow.AsString("last_error_message", ""),
+					))
+				}
+				lastStatus = fmt.Sprintf("%s Worker_Errors=[%s]", lastStatus, strings.Join(workerErrors, "; "))
+			}
+		}
 		return ioRunning == "Yes" && sqlRunning == "Yes"
 	}, 30*time.Second, 200*time.Millisecond, "replication not healthy: %s", lastStatus)
 	require.Truef(t, ok, "replication not healthy: %s", lastStatus)