// NewChord creates Chord instance
func NewChord(group *Group, callback *signatures.TaskSignature) *Chord {
// Generate a UUID for the chord callback
callback.UUID = fmt.Sprintf("chord_%v", uuid.New())
// Add a chord callback to all tasks
for _, task := range group.Tasks {
task.ChordCallback = callback
}
return &Chord{Group: group, Callback: callback}
}
// Publish places a new message on the default queue
func (amqpBroker *AMQPBroker) Publish(signature *signatures.TaskSignature) error {
_, channel, _, confirmsChan, err := amqpBroker.open()
defer channel.Close()
if err != nil {
return err
}
message, err := json.Marshal(signature)
if err != nil {
return fmt.Errorf("JSON Encode Message: %v", err)
}
signature.AdjustRoutingKey(
amqpBroker.config.ExchangeType,
amqpBroker.config.BindingKey,
amqpBroker.config.DefaultQueue,
)
if err := channel.Publish(
amqpBroker.config.Exchange, // exchange
signature.RoutingKey, // routing key
false, // mandatory
false, // immediate
amqp.Publishing{
ContentType: "application/json",
Body: message,
DeliveryMode: amqp.Persistent,
},
); err != nil {
return err
}
confirmed := <-confirmsChan
if confirmed.Ack {
return nil
}
return fmt.Errorf("Failed delivery of delivery tag: %v", confirmed.DeliveryTag)
}
// SendTask publishes a task to the default queue
func (server *Server) SendTask(signature *signatures.TaskSignature) (*backends.AsyncResult, error) {
// Make sure result backend is defined
if server.backend == nil {
return nil, errors.New("Result backend required")
}
// Auto generate a UUID if not set already
if signature.UUID == "" {
signature.UUID = fmt.Sprintf("task_%v", uuid.New())
}
// Set initial task state to PENDING
if err := server.backend.SetStatePending(signature); err != nil {
return nil, fmt.Errorf("Set State Pending: %v", err)
}
if err := server.broker.Publish(signature); err != nil {
return nil, fmt.Errorf("Publish Message: %v", err)
}
return backends.NewAsyncResult(signature, server.backend), nil
}