除了常规的PUB指令发布消息，nsq还支持延迟投递，例如发布一个延时消息：30秒后自动断开连接
支持DPUB延时投递消息
- 虽然官方文档中nsqd的http接口没有提供dpub接口，但是从nsqd的源码中可以看到是支持DPUB延时发布的。
单元测试以及使用nsq_to_file消费
- 修改nsqio/go-nsq/producer.go中的TestProducerPublish()单元测试函数，设置先发10条常规消息后发一条5秒延时消息，内容为发布时间
func TestProducerPublish(t *testing.T) {
topicName := "test"// + strconv.Itoa(int(time.Now().Unix()))
msgCount := 10
config := NewConfig()
w, _ := NewProducer("127.0.0.1:4150", config)
w.SetLogger(nullLogger, LogLevelInfo)
defer w.Stop()
for i := 0; i < msgCount; i++ {
err := w.Publish(topicName, []byte(time.Now().Format("2006/1/2 15:04:05")))
if err != nil {
t.Fatalf("error %s", err)
}
}
err := w.DeferredPublish(topicName, 5 * time.Second,[]byte(time.Now().Format("2006/1/2 15:04:05")))
//err := w.Publish(topicName, []byte("bad_test_case"))
if err != nil {
t.Fatalf("error %s", err)
}
readMessages(topicName, t, msgCount)
}
- 修改nsq_to_file/file_logger.go中router()文件写入函数格式（消费时间---消息）
func (f *FileLogger) router(r *nsq.Consumer) {
...
for {
select {
...
case m := <-f.logChan:
if f.needsFileRotate() {
f.updateFile()
sync = true
}
var buffer bytes.Buffer
buffer.Write([]byte(time.Now().Format("2006/1/2 15:04:05")))
buffer.Write([]byte("---"))
buffer.Write(m.Body)
_, err := f.writer.Write(buffer.Bytes())
//_, err := f.writer.Write(m.Body)
if err != nil {
log.Fatalf("ERROR: writing message to disk - %s", err)
}
_, err = f.writer.Write([]byte("\n"))
if err != nil {
log.Fatalf("ERROR: writing newline to disk - %s", err)
}
output[pos] = m
pos++
if pos == cap(output) {
sync = true
}
}
...
}
}
- 消费文件内容：
-
可见最后一条消息时5秒延时投递的</br>
消费文件.png
nsqd 执行DPUB指令
- 和PUB的区别是 读取多一个延时参数，并设置到msg.deferred，消息同样是使用topic.PutMessage(msg)发布到topic.memoryMsgChan再由topic.messagePump()协程处理分发给每个channel
func (p *protocolV2) DPUB(client *clientV2, params [][]byte) ([]byte, error) {
...
// 延时参数 timeoutMs
timeoutMs, err := protocol.ByteToBase10(params[2])
if err != nil {
return nil, protocol.NewFatalClientErr(err, "E_INVALID",
fmt.Sprintf("DPUB could not parse timeout %s", params[2]))
}
timeoutDuration := time.Duration(timeoutMs) * time.Millisecond
if timeoutDuration < 0 || timeoutDuration > p.ctx.nsqd.getOpts().MaxReqTimeout {
return nil, protocol.NewFatalClientErr(nil, "E_INVALID",
fmt.Sprintf("DPUB timeout %d out of range 0-%d",
timeoutMs, p.ctx.nsqd.getOpts().MaxReqTimeout/time.Millisecond))
}
...
topic := p.ctx.nsqd.GetTopic(topicName)
msg := NewMessage(topic.GenerateID(), messageBody)
// 给消息对象设置延时熟悉
msg.deferred = timeoutDuration
err = topic.PutMessage(msg)
client.PublishedMessage(topicName, 1)
return okBytes, nil
}
topic.messagePump()处理延时消息
func (t *Topic) messagePump() {
...
for i, channel := range chans {
chanMsg := msg
// copy the message because each channel
// needs a unique instance but...
// fastpath to avoid copy if its the first channel
// (the topic already created the first copy)
if i > 0 {
chanMsg = NewMessage(msg.ID, msg.Body)
chanMsg.Timestamp = msg.Timestamp
chanMsg.deferred = msg.deferred
}
// 处理延时消息
if chanMsg.deferred != 0 {
channel.PutMessageDeferred(chanMsg, chanMsg.deferred)
continue
}
err := channel.PutMessage(chanMsg)
if err != nil {
t.ctx.nsqd.logf(LOG_ERROR,
"TOPIC(%s) ERROR: failed to put msg(%s) to channel(%s) - %s",
t.name, msg.ID, channel.name, err)
}
}
}
- 由PutMessageDeferred()处理后会将延时消息放入deferredPQ队列，走超时消息的处理了流程，queueScanWorker线程处理
- 延迟参数被设置到item.Priority，再由超时处理时取出判断是否超时
func (n *NSQD) queueScanWorker(workCh chan *Channel, responseCh chan bool, closeCh chan int) {
for {
select {
case c := <-workCh:
now := time.Now().UnixNano()
dirty := false
if c.processInFlightQueue(now) {
dirty = true
}
if c.processDeferredQueue(now) {
dirty = true
}
responseCh <- dirty
case <-closeCh:
return
}
}
}
不出意外的话这应该是nsq消息队列的最后一更了，由于工作上没有实际使用所以只能想到什么写什么，后续想到其他的再补充
