Golang Worker.RequestAttempts方法代码示例

// GetWork requests one or more work units to perform.  The work unit
// attempts are associated with workerID, which need not have been
// previously registered.  If there is no work to do, may return
// neither work nor an error.
//
// Each work unit is returned as a cborrpc.PythonTuple holding the
// work spec name, work unit key as a byte slice, and work unit data
// dictionary.  If options does not contain "max_jobs" or if that
// value is 1, returns a tuple or nil, otherwise returns a slice of
// tuples (maybe 1 or none).
func (jobs *JobServer) GetWork(workerID string, options map[string]interface{}) (interface{}, string, error) {
	// This is the Big Kahuna.  The Python Coordinate server tries
	// to be extra clever with its return value, returning None if
	// there is no work, a concrete value if one work unit was
	// requested, and a list if more than one was requested, and
	// this same rule is enforced in the client code.  So, this will
	// return either exactly one PythonTuple or a list of PythonTuple.
	var (
		attempts  []coordinate.Attempt
		err       error
		gwOptions GetWorkOptions
		worker    coordinate.Worker
	)
	err = decode(&gwOptions, options)
	if err == nil {
		worker, err = jobs.Namespace.Worker(workerID)
	}
	if err == nil {
		if gwOptions.MaxJobs < 1 {
			gwOptions.MaxJobs = 1
		}
		req := coordinate.AttemptRequest{
			NumberOfWorkUnits: gwOptions.MaxJobs,
			Runtimes:          []string{""},
			WorkSpecs:         gwOptions.WorkSpecNames,
		}
		attempts, err = worker.RequestAttempts(req)
	}
	if err != nil {
		return nil, "", err
	}
	// successful return
	if gwOptions.MaxJobs == 1 {
		if len(attempts) == 0 {
			tuple := cborrpc.PythonTuple{
				Items: []interface{}{nil, nil, nil},
			}
			return tuple, "", nil
		}
		if len(attempts) == 1 {
			tuple, err := getWorkTuple(attempts[0])
			if err != nil {
				return nil, "", err
			}
			return tuple, "", nil
		}
	}
	result := make([]cborrpc.PythonTuple, len(attempts))
	for i, attempt := range attempts {
		tuple, err := getWorkTuple(attempt)
		if err != nil {
			return nil, "", err
		}
		result[i] = tuple
	}
	return result, "", nil
}

// doWork gets attempts and runs them.  It assumes it is running in its
// own goroutine.  It signals gotWork when the call to RequestAttempts
// returns, and signals finished immediately before returning.
func (w *Worker) doWork(id string, worker coordinate.Worker, ctx context.Context, gotWork chan<- bool, finished chan<- string) {
	// When we finish, signal the finished channel with our own ID
	defer func() {
		finished <- id
	}()

	attempts, err := worker.RequestAttempts(coordinate.AttemptRequest{
		Runtimes:          []string{"go"},
		NumberOfWorkUnits: w.MaxAttempts,
	})
	if err != nil {
		// Handle the error if we can, but otherwise act just like
		// we got no attempts back
		if w.ErrorHandler != nil {
			w.ErrorHandler(err)
		}
		gotWork <- false
		return
	}
	if len(attempts) == 0 {
		// Nothing to do
		gotWork <- false
		return
	}
	// Otherwise we have actual work (and at least one attempt).
	gotWork <- true

	// See if we can find a task for the work spec
	spec := attempts[0].WorkUnit().WorkSpec()
	task := spec.Name()
	data, err := spec.Data()
	if err == nil {
		aTask, present := data["task"]
		if present {
			bTask, ok := aTask.(string)
			if ok {
				task = bTask
			}
		}
	}

	// Try to find the task function
	var taskFn func(context.Context, []coordinate.Attempt)
	if err == nil {
		taskFn = w.Tasks[task]
		if taskFn == nil {
			err = fmt.Errorf("No such task function %q", task)
		}
	}

	if err == nil {
		taskCtx, cancellation := context.WithCancel(ctx)
		w.cancellations[id] = cancellation
		taskFn(taskCtx, attempts)
		// It appears to be recommended to call this; calling
		// it multiple times is documented to have no effect
		cancellation()
	} else {
		failure := map[string]interface{}{
			"traceback": err.Error(),
		}
		// Try to fail all the attempts, ignoring errors
		for _, attempt := range attempts {
			_ = attempt.Fail(failure)
		}
	}
}