package main
import (
"io"
"net/http"
)
func hello(w http.ResponseWriter, r *http.Request) {
io.WriteString(w, "Hello world!\n")
}
func main() {
http.HandleFunc("/", hello)
http.ListenAndServe(":8000", nil)
}
我有几个非常基本的HTTP服务器,所有的服务器都有这个问题。
$ ab -c 1000 -n 10000 http://127.0.0.1:8000/
This is ApacheBench, Version 2.3 <$Revision: 1604373 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
apr_socket_recv: Connection refused (61)
Total of 5112 requests completed
使用较小的并发值,事情仍然会失败。对我来说,这个问题似乎通常出现在5k-6k左右:
$ ab -c 10 -n 10000 http://127.0.0.1:8000/
This is ApacheBench, Version 2.3 <$Revision: 1604373 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
apr_socket_recv: Operation timed out (60)
Total of 6277 requests completed
事实上,你可以完全放弃并发,但问题(有时)仍然会发生:
$ ab -c 1 -n 10000 http://127.0.0.1:8000/
This is ApacheBench, Version 2.3 <$Revision: 1604373 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/
Benchmarking 127.0.0.1 (be patient)
Completed 1000 requests
Completed 2000 requests
Completed 3000 requests
Completed 4000 requests
Completed 5000 requests
Completed 6000 requests
apr_socket_recv: Operation timed out (60)
Total of 6278 requests completed
我不禁在想,我是不是遇到了某种操作系统的限制?我怎么知道呢?我该如何减轻压力呢?
发布于 2015-05-21 02:39:48
简而言之,您的端口快用完了。
osx上默认的临时端口范围是49152-65535,只有16,383个端口。由于每个ab
请求都是http/1.0
(在第一个示例中没有keepalive ),因此每个新请求都使用不同的端口。
当每个端口被使用时,它被放入一个队列中,等待tcp“最大段生存期”,该值在osx上被配置为15秒。因此,如果您在15秒内使用了超过16,383个端口,那么在进一步连接时,您将有效地受到操作系统的限制。根据哪个进程最先耗尽端口,您将从服务器获得连接错误,或者从ab
获得挂起。
您可以通过使用支持http/1.1
的负载生成器(如wrk
)或使用ab
的keepalive (-k
)选项来缓解此问题,以便根据工具的并发设置重用连接。
现在,您正在进行基准测试的服务器代码做得如此之少,以至于负载生成器的负担与服务器本身一样多,而本地操作系统和网络堆栈可能做出了很好的贡献。如果您想对http服务器进行基准测试,最好从不在同一台机器上运行的多个客户端执行一些有意义的工作。
https://stackoverflow.com/questions/30352725
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