// Start configures the NSQWriter and checks if the tasks topic exists.
// The topic is created if it does not exist.
func (self *Taskd) Start(wg *sync.WaitGroup) (err error) {
self.writer = nsq.NewWriter(self.options.MsgSinkTcpAddr)
topicExists, err := msg.TopicExists(self.options.MsgTopic, []string{self.options.MsgSourceHttpAddr})
if err != nil {
log.Fatalf("Could not query topic existance: %s", err)
}
if !topicExists {
err = msg.CreateTopicChannel(self.options.MsgTopic, self.options.MsgChannel, self.options.MsgSourceHttpAddr)
if err != nil {
log.Fatalf("Creating topic failed: %s", err)
}
}
self.wg = wg
self.wg.Add(1)
return
}
func (no *NsqOutput) Init(config interface{}) error {
no.conf = config.(*NsqOutputConfig)
no.nsqwriter = nsq.NewWriter(no.conf.Address)
return nil
}
// HandleMessage is required to comply with NSQReader's Handler interface.
// The task structure is decoded from the message body, the parameters and method
// are extracted through reflection, and finally, after execution,
// the task results are packed, serialized, and published to the topic and
// channel unique for this task.
func (self *TaskHandler) HandleMessage(message *nsq.Message) (err error) {
defer func() {
if r := recover(); r != nil {
log.Println("Task Handler panicked, but recovered", r)
}
}()
if self.options.Verbose {
log.Printf("Received task message %s", message.Id)
}
remoteTask := &Task{}
err = Decode(remoteTask, message.Body)
if err != nil {
log.Printf("ERROR: Could not decode task from message %s: %s", message.Id, err)
// publish error message to response topic
return
}
// Obtain the Value through which to call the method and its parameters
methodValue, err := getMethodValue(remoteTask)
if err != nil {
log.Printf("ERROR: Could not obtain method value for task %s, method %s: %s", remoteTask.ResponseTopic, remoteTask.Method, err)
// publish error message to response topic
return
}
methodParams, err := getMethodParams(remoteTask)
if err != nil {
log.Printf("ERROR: Could not obtain method parameters for task %s, method %s: %s", remoteTask.ResponseTopic, remoteTask.Method, err)
// publish error message to response topic
return
}
// Execute; this can panic hence the deferred recover at top
results := methodValue.Call(methodParams)
// Pack the results and return them - any actual
// method error (that is, an error in the logical execution
// of the method, as opposed to the call) will be part of these
// The client is responsible for handling that.
taskResult := &TaskResult{NewMethodState: remoteTask.MethodState,
Method: remoteTask.Method,
Returns: make([]interface{}, len(results))}
for idx := range results {
taskResult.Returns[idx] = results[idx].Interface()
}
resultBody, err := EncodeResult(taskResult)
if err != nil {
log.Printf("ERROR: Could not encode results for publishing to task %s, method %s: %s", remoteTask.ResponseTopic, remoteTask.Method, err)
// publish error message to response topic
return
}
// Dispatch result:
// Open up a writer using the options
// Write the result
// Close the writer.
resultWriter := nsq.NewWriter(self.options.MsgSinkTcpAddr)
frameType, _, err := resultWriter.Publish(remoteTask.ResponseTopic, resultBody)
if err != nil || frameType == nsq.FrameTypeError {
log.Printf("ERROR: Could not publish results of task %s, method %s: %s", remoteTask.ResponseTopic, remoteTask.Method, err)
return
}
return
}