Apache和Tomcat之间的延迟

我们有一个设置，其中我们有一个弹性LB，它将负载分布在两个Apache服务器A1和A2上。这些apache服务器呈现一些php页面，主要将API请求重定向到tomcat应用程序服务器T1和T2，如下图所示：

Incoming Request
    |
    |
    |
    \/
    LB
    /\
   /  \
  /    \
A1     A2
|\     /|
| \   / |
|  \ /  |
|  / \  |
T1      T2

我们最近开始注意到apache和tomcat之间的延迟。以下是apache mod_slow log和tomcat access log中针对同一请求的日志行示例：

APACHE_MOD_SLOW: VNSdtwoAAJkAACnXb-cAAACJ [06/Feb/2015:16:25:51 +0530] elapsed: 50.58 cpu: 0.00(usr)/0.00(sys) pid: 10711 ip: 10.0.0.153 host: www.example.com:443 reqinfo: GET /data/v1/url?url=test-508324 HTTP/1.1

TOMCAT: [06/Feb/2015:16:26:42 +0530] "GET /data/v1/url?url=test-508324 HTTP/1.1" 200 65 10

Apache表示，收到的请求是在

06/Feb/2015:16:25:51+0530

时发出的，处理请求需要

50秒。而tomcat表示只需
10毫秒
即可处理请求，而它是在
06/Feb/2015:16:26:42+0530
收到请求的

这意味着apache花了将近50秒的时间连接并将整个请求发送给tomcat。Apache正在使用
mod\u proxy\u ajp
连接到Apache。以下是配置：

<Proxy balancer://prod>
   BalancerMember ajp://127.0.0.1:8009 route=jvmRoute-8009 connectiontimeout=1 retry=300
   BalancerMember ajp://10.0.0.153:8009 route=jvmRoute-8009 connectiontimeout=1 retry=300    
   ProxySet lbmethod=byrequests
</Proxy>

下面的观察让我相信，糟糕的性能取决于事件的顺序，因为测试中没有一个请求执行得那么糟糕

版本：
Apache:2.2.4
Tomcat:8.0.16

是否知道延迟来自何处以及如何减少延迟？
通常，这种延迟表示响应的内容长度无效，并且用户代理（在本例中为httpd）在最终超时连接之前等待其预期的其余响应。检查您的响应头并使用-k和ab来使用keep-alive，因为这更可能触发此类问题。@马克：我们可能不是这种情况，因为tomcat最终以200状态代码提供了请求，假设Apache和tomcat以及lb和Apache之间存在keep-alive。如果没有，请检查netstat。@Khanna111GauravKhanna:keep-alive是否存在DNS/反向DNS问题？我认为tcpdump或wireshark可以提供很多信息。甚至netstat。您可以使用类似于：watch-n1“netstat-ntp | grep8009”的内容来监视连接的情况。
<Connector port="8009" protocol="AJP/1.3" redirectPort="8443" maxThreads="4096" minSpareThreads="25" maxSpareThreads="75"/>

ab -n5000 -c5 https://example.com/test/100001                                        

Requests per second:    13.67 [#/sec] (mean)                                        
Time per request:       365.851 [ms] (mean)                                        
Time per request:       73.170 [ms] (mean, across all concurrent requests)                                        
Transfer rate:          79.96 [Kbytes/sec] received                                        

Connection Times (ms)                                        
              min  mean[+/-sd] median   max                                        
Connect:      236  267  95.5    247    3401                                        
Processing:    83   98  58.6     89    1959                                        
Waiting:       82   96  57.5     87    1959                                        
Total:        319  365 134.0    338    3571                                        

Percentage of the requests served within a certain time (ms)                                        
  50%    338                                        
  66%    347                                        
  75%    356                                        
  80%    364                                        
  90%    399                                        
  95%    477                                        
  98%    689                                        
  99%    869                                        
 100%   3571 (longest request)

ab -n5000 -c5 http://example.com/test/100001                                        

Time per request:       186.015 [ms] (mean)
Time per request:       37.203 [ms] (mean, across all concurrent requests)
Transfer rate:          155.55 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:       74   79  33.4     76    1278
Processing:    83  107  82.3     91    3964
Waiting:       82  105  60.9     89     940
Total:        157  186  90.1    168    4042

Percentage of the requests served within a certain time (ms)
  50%    168
  66%    174
  75%    180
  80%    184
  90%    211
  95%    259
  98%    379
  99%    507
 100%   4042 (longest request)

ab -n5000 -c5 http://IP:8080/test/100001                                        

Requests per second:    31.32 [#/sec] (mean)
Time per request:       159.624 [ms] (mean)
Time per request:       31.925 [ms] (mean, across all concurrent requests)
Transfer rate:          181.30 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:       71   76  68.4     73    3079
Processing:    78   84  13.1     81     594
Waiting:       77   83   6.5     81     185
Total:        149  159  71.2    154    3313

Percentage of the requests served within a certain time (ms)
  50%    154
  66%    157
  75%    160
  80%    161
  90%    166
  95%    171
  98%    177
  99%    189
 100%   3313 (longest request)