task runner to avoid running task if terminal

client/allocrunner/alloc_runner_unix_test.go

@@ -131,3 +131,87 @@ func TestAllocRunner_Restore_RunningTerminal(t *testing.T) {
 	require.Equal(t, events[2].Type, structs.TaskStarted)
 	require.Equal(t, events[3].Type, structs.TaskTerminated)
 }
+
+// TestAllocRunner_Restore_Completed asserts that restoring a completed
+// batch alloc doesn't run it again
+func TestAllocRunner_Restore_CompletedBatch(t *testing.T) {
+	t.Parallel()
+
+	// 1. Run task and wait for it to complete
+	// 2. Start new alloc runner
+	// 3. Assert task didn't run again
+
+	alloc := mock.Alloc()
+	alloc.Job.Type = structs.JobTypeBatch
+	task := alloc.Job.TaskGroups[0].Tasks[0]
+	task.Driver = "mock_driver"
+	task.Config = map[string]interface{}{
+		"run_for": "2ms",
+	}
+
+	conf, cleanup := testAllocRunnerConfig(t, alloc.Copy())
+	defer cleanup()
+
+	// Maintain state for subsequent run
+	conf.StateDB = state.NewMemDB(conf.Logger)
+
+	// Start and wait for task to be running
+	ar, err := NewAllocRunner(conf)
+	require.NoError(t, err)
+	go ar.Run()
+	defer destroy(ar)
+
+	testutil.WaitForResult(func() (bool, error) {
+		s := ar.AllocState()
+		if s.ClientStatus != structs.AllocClientStatusComplete {
+			return false, fmt.Errorf("expected complete, got %s", s.ClientStatus)
+		}
+		return true, nil
+	}, func(err error) {
+		require.NoError(t, err)
+	})
+
+	// once job finishes, it shouldn't run again
+	require.False(t, ar.shouldRun())
+	initialRunEvents := ar.AllocState().TaskStates[task.Name].Events
+	require.Len(t, initialRunEvents, 4)
+
+	ls, ts, err := conf.StateDB.GetTaskRunnerState(alloc.ID, task.Name)
+	require.NoError(t, err)
+	require.NotNil(t, ls)
+	require.Equal(t, structs.TaskStateDead, ts.State)
+
+	// Start a new alloc runner and assert it gets stopped
+	conf2, cleanup2 := testAllocRunnerConfig(t, alloc)
+	defer cleanup2()
+
+	// Use original statedb to maintain hook state
+	conf2.StateDB = conf.StateDB
+
+	// Restore, start, and wait for task to be killed
+	ar2, err := NewAllocRunner(conf2)
+	require.NoError(t, err)
+
+	require.NoError(t, ar2.Restore())
+
+	go ar2.Run()
+	defer destroy(ar2)
+
+	// AR waitCh must be closed even when task doesn't run again
+	select {
+	case <-ar2.WaitCh():
+	case <-time.After(10 * time.Second):
+		require.Fail(t, "alloc.waitCh wasn't closed")
+	}
+
+	// TR waitCh must be closed too!
+	select {
+	case <-ar2.tasks[task.Name].WaitCh():
+	case <-time.After(10 * time.Second):
+		require.Fail(t, "tr.waitCh wasn't closed")
+	}
+
+	// Assert that events are unmodified, which they would if task re-run
+	events := ar2.AllocState().TaskStates[task.Name].Events
+	require.Equal(t, initialRunEvents, events)
+}

client/allocrunner/taskrunner/task_runner.go

@@ -394,6 +394,22 @@ func (tr *TaskRunner) Run() {
 	defer close(tr.waitCh)
 	var result *drivers.ExitResult
 
+	tr.stateLock.RLock()
+	dead := tr.state.State == structs.TaskStateDead
+	tr.stateLock.RUnlock()
+
+	// if restoring a dead task, ensure that task is cleared and all post hooks
+	// are called without additional state updates
+	if dead {
+		// clear driver handle if it was successfully restored on
+		// already dead task
+		tr.clearDriverHandle()
+		if err := tr.stop(); err != nil {
+			tr.logger.Error("stop failed on terminal task", "error", err)
+		}
+		return
+	}
+
 	// Updates are handled asynchronously with the other hooks but each
 	// triggered update - whether due to alloc updates or a new vault token
 	// - should be handled serially.
@@ -899,7 +915,7 @@ func (tr *TaskRunner) Restore() error {
 		}
 
 		alloc := tr.Alloc()
-		if alloc.TerminalStatus() || alloc.Job.Type == structs.JobTypeSystem {
+		if tr.state.State == structs.TaskStateDead || alloc.TerminalStatus() || alloc.Job.Type == structs.JobTypeSystem {
 			return nil
 		}