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我试图在GO使用GO语言在gnatsd中实现请求/响应functinonality，并且我意识到gnatsd不会以异步方式回复请求。对请求的NATS异步回复不是异步
我开始使用NATS github示例https://github.com/nats-io/go-nats/tree/master/examples进行调查 - 示例nats-req.go和nats-rply.go。这些例子效果很好。
然后，我修改它们只是为了测试gnatsd上的并行请求，并提供一些调试信息，其中处理异步回复的goroutine ID。 有修改示例的源代码。
nats-rply.go已修改为仅返回传入请求的文本以及有关当前goroutine ID的信息。我还增加了异步处理功能1秒睡眠模拟一些处理时间。
package main
import (
"fmt"
"github.com/nats-io/go-nats"
"flag"
"log"
"runtime"
"time"
"bytes"
"strconv"
)
// NOTE: Use tls scheme for TLS, e.g. nats-rply -s tls://demo.nats.io:4443 foo hello
func usage() {
log.Fatalf("Usage: nats-rply [-s server][-t] <subject> \n")
}
func printMsg(m *nats.Msg, i int) {
log.Printf("[#%d] Received on [%s]: '%s'\n", i, m.Subject, string(m.Data))
}
func main() {
log.Printf("Main goroutine ID:%d\n", getGID())
var urls = flag.String("s", nats.DefaultURL, "The nats server URLs (separated by comma)")
var showTime = flag.Bool("t", false, "Display timestamps")
//log.SetFlags(0)
flag.Usage = usage
flag.Parse()
args := flag.Args()
if len(args) < 1 {
usage()
}
nc, err := nats.Connect(*urls)
if err != nil {
log.Fatalf("Can't connect: %v\n", err)
}
subj, i := args[0], 0
nc.Subscribe(subj, func(msg *nats.Msg) {
i++
printMsg(msg, i)
//simulation of some processing time
time.Sleep(1 * time.Second)
newreply := []byte(fmt.Sprintf("REPLY TO request \"%s\", GoroutineId:%d", string(msg.Data), getGID()))
nc.Publish(msg.Reply, []byte(newreply))
})
nc.Flush()
if err := nc.LastError(); err != nil {
log.Fatal(err)
}
log.Printf("Listening on [%s]\n", subj)
if *showTime {
log.SetFlags(log.LstdFlags)
}
runtime.Goexit()
}
func getGID() uint64 {
b := make([]byte, 64)
b = b[:runtime.Stack(b, false)]
b = bytes.TrimPrefix(b, []byte("goroutine "))
b = b[:bytes.IndexByte(b, ' ')]
n, _ := strconv.ParseUint(string(b), 10, 64)
return n
}
NATS-req.go已被修改为发送在单独的10个够程10个请求开始并行地，请求超时已被设置为3,5秒。我尝试了使用共享NATS连接（函数oneReq（））的goroutines，并且还使用自己的NATS连接（函数onReqSeparateConnect（））构造了goroutine - 同样的失败结果。
package main
import (
"flag"
"fmt"
"github.com/nats-io/go-nats"
"sync"
"time"
"log"
)
// NOTE: Use tls scheme for TLS, e.g. nats-req -s tls://demo.nats.io:4443 foo hello
func usage() {
log.Fatalf("Usage: nats-req [-s server (%s)] <subject> \n", nats.DefaultURL)
}
func main() {
//var urls = flag.String("s", nats.DefaultURL, "The nats server URLs (separated by comma)")
//log.SetFlags(0)
flag.Usage = usage
flag.Parse()
args := flag.Args()
if len(args) < 1 {
usage()
}
nc, err := nats.Connect(nats.DefaultURL)
if err != nil {
log.Fatalf("Can't connect: %v\n", err)
}
defer nc.Close()
subj := args[0]
var wg sync.WaitGroup
wg.Add(10)
for i := 1; i <= 10; i++ {
//go oneReq(subj, fmt.Sprintf("Request%d", i), nc, &wg)
go oneReqSeparateConnect(subj, fmt.Sprintf("Request%d", i), &wg)
}
wg.Wait()
}
func oneReq(subj string, payload string, nc *nats.Conn, wg *sync.WaitGroup) {
defer wg.Done()
msg, err := nc.Request(subj, []byte(payload), 3500*time.Millisecond)
if err != nil {
if nc.LastError() != nil {
log.Printf("Error in Request: %v\n", nc.LastError())
}
log.Printf("Error in Request: %v\n", err)
} else {
log.Printf("Published [%s] : '%s'\n", subj, payload)
log.Printf("Received [%v] : '%s'\n", msg.Subject, string(msg.Data))
}
}
func oneReqSeparateConnect(subj string, payload string, wg *sync.WaitGroup) {
defer wg.Done()
nc, err := nats.Connect(nats.DefaultURL)
if err != nil {
log.Printf("Can't connect: %v\n", err)
return
}
defer nc.Close()
msg, err := nc.Request(subj, []byte(payload), 3500*time.Millisecond)
if err != nil {
if nc.LastError() != nil {
log.Printf("Error in Request: %v\n", nc.LastError())
}
log.Printf("Error in Request: %v\n", err)
} else {
log.Printf("Published [%s] : '%s'\n", subj, payload)
log.Printf("Received [%v] : '%s'\n", msg.Subject, string(msg.Data))
}
}
而且有结果 - 不受欢迎的行为，它看起来是NATS-rply.go处理传入reqests只创建一个够程和请求以串行的方式进行处理。 nats-req.go一次发送全部10个请求，超时设置为3,5秒。 nats-rply.go以串行方式以一秒间隔开始响应请求，因此只有3个请求被满足，直到超过3,5秒超时 - 其余请求超时。响应消息还包含GoroutineID，对于所有传入的请求都是相同的！即使再次启动nats-req时，goroutine id也是一样，只有在重新启动nats-rply.go服务器时，ID才会更改。
在NATSNATS-req.go日志
D:\PRAC\TSP\AMON>nats-req foo
2017/08/29 18:46:48 Sending: 'Request9'
2017/08/29 18:46:48 Sending: 'Request7'
2017/08/29 18:46:48 Sending: 'Request10'
2017/08/29 18:46:48 Sending: 'Request4'
2017/08/29 18:46:48 Sending: 'Request8'
2017/08/29 18:46:48 Sending: 'Request6'
2017/08/29 18:46:48 Sending: 'Request1'
2017/08/29 18:46:48 Sending: 'Request5'
2017/08/29 18:46:48 Sending: 'Request2'
2017/08/29 18:46:48 Sending: 'Request3'
2017/08/29 18:46:49 Published [foo] : 'Request9'
2017/08/29 18:46:49 Received [_INBOX.xrsXYOB2QmW1f52pkfLHya.xrsXYOB2QmW1f52pkfLHzJ] : 'REPLY TO request "Request9", GoroutineId:36'
2017/08/29 18:46:50 Published [foo] : 'Request7'
2017/08/29 18:46:50 Received [_INBOX.xrsXYOB2QmW1f52pkfLI02.xrsXYOB2QmW1f52pkfLI0l] : 'REPLY TO request "Request7", GoroutineId:36'
2017/08/29 18:46:51 Published [foo] : 'Request10'
2017/08/29 18:46:51 Received [_INBOX.xrsXYOB2QmW1f52pkfLI1U.xrsXYOB2QmW1f52pkfLI2D] : 'REPLY TO request "Request10", GoroutineId:36'
2017/08/29 18:46:52 Error in Request: nats: timeout
2017/08/29 18:46:52 Error in Request: nats: timeout
2017/08/29 18:46:52 Error in Request: nats: timeout
2017/08/29 18:46:52 Error in Request: nats: timeout
2017/08/29 18:46:52 Error in Request: nats: timeout
2017/08/29 18:46:52 Error in Request: nats: timeout
2017/08/29 18:46:52 Error in Request: nats: timeout
NATS-rply.go日志
C:\Users\belunek>nats-rply foo
2017/08/29 18:46:46 Main goroutine ID:1
2017/08/29 18:46:46 Listening on [foo]
2017/08/29 18:46:48 [#1] Received on [foo]: 'Request9'
2017/08/29 18:46:49 [#2] Received on [foo]: 'Request7'
2017/08/29 18:46:50 [#3] Received on [foo]: 'Request10'
2017/08/29 18:46:51 [#4] Received on [foo]: 'Request4'
2017/08/29 18:46:52 [#5] Received on [foo]: 'Request8'
2017/08/29 18:46:53 [#6] Received on [foo]: 'Request6'
2017/08/29 18:46:54 [#7] Received on [foo]: 'Request1'
2017/08/29 18:46:55 [#8] Received on [foo]: 'Request5'
2017/08/29 18:46:56 [#9] Received on [foo]: 'Request2'
2017/08/29 18:46:57 [#10] Received on [foo]: 'Request3'
请任何想法，如何正确地执行请求/响应通信与asyns （并行）响应处理？ 感谢您的任何信息。
非常感谢您的澄清和工作示例！它工作完美无瑕。 –
一个小问题，如果你想让你的计数器正常工作，你需要用一个互斥体来包裹它，例如， https://stackoverflow.com/questions/16783273/golang-best-way-to-implement-global-counters-for-highly-concurrent-applications –