我试图使用GO语言在gnatsd中实现请求/响应功能，但我意识到gnatsd不会以异步方式响应请求。
我使用NATS github示例https://github.com/nats-io/go-nats/tree/master/examples-示例nats-req.go和nats-rply.go开始了调查。这些示例效果很好。
然后，我修改了它们，只是为了在gnatsd上测试并行请求，并提供一些调试信息，在该信息中将处理异步回复的goroutine ID。
有修改示例的源代码。
nats-rply.go 已修改为仅返回包含当前goroutine ID信息的传入请求文本。我还为异步处理功能添加了1秒 sleep 来模拟一些处理时间。
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 已修改为在并行启动的10个goroutine中分别发送10个请求，请求超时已设置为3.5秒。我尝试了具有共享NATS连接的goroutines(函数oneReq())，还尝试了具有其自己的NATS连接的goroutines(函数onReqSeparateConnect())，但结果相同。
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))
}
}
结果是-不必要的行为，看起来nats-rply.go仅创建一个goroutine来处理传入的请求，并且请求以串行方式处理。
nats-req.go一次发送所有10个请求，并将超时设置为3,5秒。 nats-rply.go开始以串行方式以一秒钟的间隔响应请求，因此只有3个请求得到满足，直到突破了3.5秒的超时时间为止-其余请求超时。响应消息还包含GoroutineID，该ID对于所有传入请求都是相同的!即使再次启动nats-req时，goroutine ID也相同，仅当重新启动nats-rply.go服务器时，该ID才会更改。
nats-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'
请提出任何想法，如何在具有asyns(并行)响应处理的NATS中正确实现请求/响应通信？
感谢您提供任何信息。
最佳答案
Gnatsd以异步方式回复Request，但它不会为每个请求启动goroutine，而只是纯异步。并且由于您使用time.Sleep模拟了处理负载，该加载会暂停调用goroutine，因此看起来像同步处理。如果您修改示例以使用goroutine，则一切正常。
...
nc.Subscribe(subj, func(msg *nats.Msg) {
go handler(msg, i, nc)
})
...
func handler(msg *nats.Msg, i int, nc *nats.Conn) {
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))
}
输出:
./nats-rply test
2017/08/30 00:17:05 Main goroutine ID:1
2017/08/30 00:17:05 Listening on [test]
2017/08/30 00:17:11 [#1] Received on [test]: 'Request6'
2017/08/30 00:17:11 [#1] Received on [test]: 'Request5'
2017/08/30 00:17:11 [#1] Received on [test]: 'Request1'
2017/08/30 00:17:11 [#1] Received on [test]: 'Request8'
2017/08/30 00:17:11 [#1] Received on [test]: 'Request3'
2017/08/30 00:17:11 [#1] Received on [test]: 'Request7'
2017/08/30 00:17:11 [#1] Received on [test]: 'Request9'
2017/08/30 00:17:11 [#1] Received on [test]: 'Request4'
2017/08/30 00:17:11 [#1] Received on [test]: 'Request2'
2017/08/30 00:17:11 [#1] Received on [test]: 'Request10'
./nats-req test
2017/08/30 00:17:12 Published [test] : 'Request3'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm6Bq] : 'REPLY TO request "Request3", GoroutineId:37'
2017/08/30 00:17:12 Published [test] : 'Request7'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm5z6] : 'REPLY TO request "Request7", GoroutineId:42'
2017/08/30 00:17:12 Published [test] : 'Request10'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm5wY] : 'REPLY TO request "Request10", GoroutineId:43'
2017/08/30 00:17:12 Published [test] : 'Request5'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm6EO] : 'REPLY TO request "Request5", GoroutineId:34'
2017/08/30 00:17:12 Published [test] : 'Request8'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm66k] : 'REPLY TO request "Request8", GoroutineId:36'
2017/08/30 00:17:12 Published [test] : 'Request1'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm64C] : 'REPLY TO request "Request1", GoroutineId:35'
2017/08/30 00:17:12 Published [test] : 'Request2'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm6Gw] : 'REPLY TO request "Request2", GoroutineId:41'
2017/08/30 00:17:12 Published [test] : 'Request4'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm69I] : 'REPLY TO request "Request4", GoroutineId:40'
2017/08/30 00:17:12 Published [test] : 'Request9'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm61e] : 'REPLY TO request "Request9", GoroutineId:39'
2017/08/30 00:17:12 Published [test] : 'Request6'
2017/08/30 00:17:12 Received [_INBOX.xoG573m0V7dVoIJxojm5u0] : 'REPLY TO request "Request6", GoroutineId:38'
关于asynchronous - NATS异步答复请求不是异步的，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/45944632/