deadlock mitigation redux (#79)

engine/storage/mysql/query.sql

@@ -67,6 +67,17 @@ WHERE
   c.step_id IS NULL AND
   s.workflow_name = ?;
 
+-- name: DeleteWorkflowStepHavingNoCommandsByStepID :exec
+DELETE
+  s
+FROM
+  steps s
+  LEFT JOIN id_commands c
+    ON s.id = c.step_id
+WHERE
+  c.step_id IS NULL AND
+  s.id = ?;
+
 -- name: UpdateIDCommandTimestamp :exec
 UPDATE
   id_commands
@@ -116,26 +127,21 @@ FROM
 WHERE
   id = ?;
 
--- name: GetIDCommandsByStepID :many
+-- name: GetIDCommandsByStepIDAndLock :many
 SELECT
-  command_uuid,
-  request_type,
-  result
+  ic.command_uuid,
+  ic.request_type,
+  ic.result
 FROM
-  id_commands
-WHERE
-  enrollment_id = ? AND
-  step_id = ? AND
-  completed != 0;
-
--- name: LockIDCommandsByStepID :exec
-SELECT
-  command_uuid
-FROM
-  id_commands
+  id_commands ic
+  INNER JOIN steps s
+    ON ic.step_id = s.id
+  LEFT JOIN step_commands sc
+    ON sc.step_id = s.id
 WHERE
-  enrollment_id = ? AND
-  step_id = ?
+  ic.enrollment_id = ? AND
+  s.id = ? AND
+  ic.completed != 0
 FOR UPDATE;
 
 -- name: RemoveIDCommandsByStepID :exec

engine/storage/mysql/storage.go

@@ -97,17 +97,9 @@ func (s *MySQLStorage) StoreCommandResponseAndRetrieveCompletedStep(ctx context.
 			Commands: []storage.StepCommandResult{*sc},
 		}
 
-		err = qtx.LockIDCommandsByStepID(ctx, sqlc.LockIDCommandsByStepIDParams{
+		cmdR, err := qtx.GetIDCommandsByStepIDAndLock(ctx, sqlc.GetIDCommandsByStepIDAndLockParams{
 			EnrollmentID: id,
-			StepID:       cmdCt.StepID,
-		})
-		if err != nil {
-			return fmt.Errorf("lock commands by step by id (%d): %w", cmdCt.StepID, err)
-		}
-
-		cmdR, err := qtx.GetIDCommandsByStepID(ctx, sqlc.GetIDCommandsByStepIDParams{
-			EnrollmentID: id,
-			StepID:       cmdCt.StepID,
+			ID:           cmdCt.StepID,
 		})
 		if err != nil {
 			return fmt.Errorf("get id commands by step by id (%d): %w", cmdCt.StepID, err)
@@ -130,9 +122,9 @@ func (s *MySQLStorage) StoreCommandResponseAndRetrieveCompletedStep(ctx context.
 			return fmt.Errorf("remove id commands by step by id (%d): %w", cmdCt.StepID, err)
 		}
 
-		err = qtx.DeleteWorkflowStepHavingNoCommandsByWorkflowName(ctx, sd.WorkflowName)
+		err = qtx.DeleteWorkflowStepHavingNoCommandsByStepID(ctx, cmdCt.StepID)
 		if err != nil {
-			return fmt.Errorf("delete workflow with no commands (%s): %w", sd.WorkflowName, err)
+			return fmt.Errorf("delete workflow with no commands (%d): %w", cmdCt.StepID, err)
 		}
 
 		return nil