Tcp用express表示在nodejs中延迟了ack
我正在为nginx做压力testing，并使用nodejs后端。 我发现延迟Keepalive。 我从testing中删除了nginx，并且遇到同样的问题。
我在用着：
- ApacheBench，版本2.3
- 节点v0.8.14。
- Ubuntu 12.04.1 LTS
- Express 3.0.3
源代码是：
var express = require('express'); var cluster = require('cluster'); var numCPUs = require('os').cpus().length; if (cluster.isMaster) { for (var i = 0; i < numCPUs; i++) { cluster.fork(); } cluster.on('exit', function(worker, code, signal) { console.log('worker ' + worker.process.pid + ' died'); }); } else { var buffer = new Buffer(1048576); buffer.fill("a"); var app = express(); app.listen(8080); app.get('/test', function(req, res){ setTimeout(function () { res.set('Content-Type', 'text/html'); res.send(buffer.slice(0, req.query.size)) }, req.query.delay); }); } tcpdump示例没有keepalive： ab -c 1 -n 10 -r "172.16.76.253:8080/test?size=1024&delay=100"
10:58:59.403876 IP 172.16.180.47.57380 > 172.16.76.253.http-alt: Flags [P.], seq 1:122, ack 1, win 15, options [nop,nop,TS val 65479762 ecr 362284218], length 121 10:58:59.403961 IP 172.16.76.253.http-alt > 172.16.180.47.57380: Flags [.], ack 122, win 29, options [nop,nop,TS val 362284218 ecr 65479762], length 0 10:58:59.504631 IP 172.16.76.253.http-alt > 172.16.180.47.57380: Flags [P.], seq 1:146, ack 122, win 29, options [nop,nop,TS val 362284243 ecr 65479762], length 145 10:58:59.504890 IP 172.16.76.253.http-alt > 172.16.180.47.57380: Flags [FP.], seq 146:1170, ack 122, win 29, options [nop,nop,TS val 362284243 ecr 65479762], length 1024 10:58:59.505727 IP 172.16.180.47.57380 > 172.16.76.253.http-alt: Flags [.], ack 146, win 17, options [nop,nop,TS val 65479787 ecr 362284243], length 0 10:58:59.505741 IP 172.16.180.47.57380 > 172.16.76.253.http-alt: Flags [.], ack 1171, win 21, options [nop,nop,TS val 65479787 ecr 362284243], length 0
ab结果：
Server Hostname: 172.16.76.253 Server Port: 8080 Document Path: /test?size=1024&delay=100 Document Length: 1024 bytes Concurrency Level: 1 Time taken for tests: 1.025 seconds Complete requests: 10 Failed requests: 0 Write errors: 0 Total transferred: 11690 bytes HTML transferred: 10240 bytes Requests per second: 9.75 [#/sec] (mean) Time per request: 102.530 [ms] (mean) Time per request: 102.530 [ms] (mean, across all concurrent requests) Transfer rate: 11.13 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 1 1 0.1 1 1 Processing: 101 102 0.5 102 102 Waiting: 101 102 0.5 102 102 Total: 102 102 0.6 103 103 WARNING: The median and mean for the total time are not within a normal deviation These results are probably not that reliable. Percentage of the requests served within a certain time (ms) 50% 103 66% 103 75% 103 80% 103 90% 103 95% 103 98% 103 99% 103 100% 103 (longest request)
带keepalive的tcpdump示例ab -c 1 -n 10 -k -r "172.16.76.253:8080/test?size=1024&delay=100"
11:00:12.567741 IP 172.16.180.47.57385 > 172.16.76.253.http-alt: Flags [P.], seq 1306:1451, ack 10567, win 26, options [nop,nop,TS val 65498053 ecr 362302509], length 145 11:00:12.567761 IP 172.16.76.253.http-alt > 172.16.180.47.57385: Flags [.], ack 1451, win 50, options [nop,nop,TS val 362302509 ecr 65498053], length 0 11:00:12.668837 IP 172.16.76.253.http-alt > 172.16.180.47.57385: Flags [P.], seq 10567:10717, ack 1451, win 50, options [nop,nop,TS val 362302534 ecr 65498053], length 150 11:00:12.706745 IP 172.16.180.47.57385 > 172.16.76.253.http-alt: Flags [.], ack 10717, win 26, options [nop,nop,TS val 65498088 ecr 362302534], length 0 11:00:12.706765 IP 172.16.76.253.http-alt > 172.16.180.47.57385: Flags [P.], seq 10717:11741, ack 1451, win 50, options [nop,nop,TS val 362302544 ecr 65498088], length 1024 11:00:12.707901 IP 172.16.180.47.57385 > 172.16.76.253.http-alt: Flags [F.], seq 1451, ack 11741, win 26, options [nop,nop,TS val 65498088 ecr 362302544], length 0 11:00:12.708141 IP 172.16.76.253.http-alt > 172.16.180.47.57385: Flags [F.], seq 11741, ack 1452, win 50, options [nop,nop,TS val 362302544 ecr 65498088], length 0
ab结果：
Server Hostname: 172.16.76.253 Server Port: 8080 Document Path: /test?size=1024&delay=100 Document Length: 1024 bytes Concurrency Level: 1 Time taken for tests: 1.361 seconds Complete requests: 10 Failed requests: 0 Write errors: 0 Keep-Alive requests: 10 Total transferred: 11740 bytes HTML transferred: 10240 bytes Requests per second: 7.35 [#/sec] (mean) Time per request: 136.073 [ms] (mean) Time per request: 136.073 [ms] (mean, across all concurrent requests) Transfer rate: 8.43 [Kbytes/sec] received Connection Times (ms) min mean[+/-sd] median max Connect: 0 0 0.3 0 1 Processing: 103 136 11.6 140 140 Waiting: 100 101 0.7 101 102 Total: 104 136 11.3 140 140 Percentage of the requests served within a certain time (ms) 50% 140 66% 140 75% 140 80% 140 90% 140 95% 140 98% 140 99% 140 100% 140 (longest request)
nodejs以两个包发送响应，一个包含头部，一个包含数据，并在第一个包之后等待ack。
我尝试设置sysctl net.ipv4.tcp_slow_start_after_idle = 0 && sysctl net.ipv4.route.flush = 1，但它没有任何效果。
使用Keepalive时，会有40毫秒的额外延迟。 问题是：多余的40ms从何时起？ 也许我做错了？
这是一个错误。 它在这里修复。
问题是4415
我通过res.send(buffer.slice(0, req.query.size).toString())将res.send(buffer.slice(0, req.query.size))更改为本testing的解决方法。