搭建服务以后，会对其做压力测试，这里选择ab压力测试

ab的概念:
ab是ApacheBench命令的缩写。

ab的原理:
ab命令会创建多个并发访问线程，模拟多个访问者同时对某一URL地址进行访问。它的测试目标是基于URL的，因此，它既可以用来测试apache的负载压力，也可以测试nginx等其它Web服务器的压力。

ab的安装:
[root@k8smaster k8s-cluster]# yum install httpd-tools

ab参数说明:
[root@k8smaster ~]# ab --help
ab: wrong number of arguments
Usage: ab [options] [http[s]://]hostname[:port]/path
Options are:
    -n requests     Number of requests to perform
    -c concurrency  Number of multiple requests to make at a time
    -t timelimit    Seconds to max. to spend on benchmarking
                    This implies -n 50000
    -s timeout      Seconds to max. wait for each response
                    Default is 30 seconds
    -b windowsize   Size of TCP send/receive buffer, in bytes
    -B address      Address to bind to when making outgoing connections
    -p postfile     File containing data to POST. Remember also to set -T
    -u putfile      File containing data to PUT. Remember also to set -T
    -T content-type Content-type header to use for POST/PUT data, eg.
                    'application/x-www-form-urlencoded'
                    Default is 'text/plain'
    -v verbosity    How much troubleshooting info to print
    -w              Print out results in HTML tables
    -i              Use HEAD instead of GET
    -x attributes   String to insert as table attributes
    -y attributes   String to insert as tr attributes
    -z attributes   String to insert as td or th attributes
    -C attribute    Add cookie, eg. 'Apache=1234'. (repeatable)
    -H attribute    Add Arbitrary header line, eg. 'Accept-Encoding: gzip'
                    Inserted after all normal header lines. (repeatable)
    -A attribute    Add Basic WWW Authentication, the attributes
                    are a colon separated username and password.
    -P attribute    Add Basic Proxy Authentication, the attributes
                    are a colon separated username and password.
    -X proxy:port   Proxyserver and port number to use
    -V              Print version number and exit
    -k              Use HTTP KeepAlive feature
    -d              Do not show percentiles served table.
    -S              Do not show confidence estimators and warnings.
    -q              Do not show progress when doing more than 150 requests
    -g filename     Output collected data to gnuplot format file.
    -e filename     Output CSV file with percentages served
    -r              Don't exit on socket receive errors.
    -h              Display usage information (this message)
    -Z ciphersuite  Specify SSL/TLS cipher suite (See openssl ciphers)
    -f protocol     Specify SSL/TLS protocol
                    (SSL3, TLS1, TLS1.1, TLS1.2 or ALL)


-n：在测试会话中所执行的请求个数。默认时，仅执行一个请求。

-c：一次产生的请求个数。默认是一次一个。

ab -c 100 -n 200 http://192.168.123.142/
上面的语句表示有100个并发访问，每秒总共有200个请求，在此情况下进行压力测试。


ab性能指标:
1、吞吐率（Requests per second）
服务器并发处理能力的量化描述，单位是reqs/s，指的是在某个并发用户数下单位时间内处理的请求数。某个并发用户数下单位时间内能处理的最大请求数，称之为最大吞吐率。

记住：吞吐率是基于并发用户数的。这句话代表了两个含义：
a、吞吐率和并发用户数相关
b、不同的并发用户数下，吞吐率一般是不同的

计算公式：总请求数/处理完成这些请求数所花费的时间，即
Request per second=Complete requests/Time taken for tests

必须要说明的是，这个数值表示当前机器的整体性能，值越大越好。

2、并发连接数（The number of concurrent connections）
并发连接数指的是某个时刻服务器所接受的请求数目，简单的讲，就是一个会话。

3、并发用户数（Concurrency Level）
要注意区分这个概念和并发连接数之间的区别，一个用户可能同时会产生多个会话，也即连接数。在HTTP/1.1下，IE7支持两个并发连接，IE8支持6个并发连接，FireFox3支持4个并发连接，所以相应的，我们的并发用户数就得除以这个基数。

4、用户平均请求等待时间（Time per request）

计算公式：处理完成所有请求数所花费的时间/（总请求数/并发用户数），即：
Time per request=Time taken for tests/（Complete requests/Concurrency Level）

5、服务器平均请求等待时间（Time per request:across all concurrent requests）

计算公式：处理完成所有请求数所花费的时间/总请求数，即：
Time taken for/testsComplete requests
可以看到，它是吞吐率的倒数。

同时，它也等于用户平均请求等待时间/并发用户数，即
Time per request/Concurrency Level


ad压力测试案例:
[root@k8smaster k8s-cluster]# ab -n 1000 -c 10 https://test.abc.com/v1/test/helloword
This is ApacheBench, Version 2.3 <$Revision: 1430300 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking test.abc.com (be patient)
Completed 100 requests
Completed 200 requests
Completed 300 requests
Completed 400 requests
Completed 500 requests
Completed 600 requests
Completed 700 requests
Completed 800 requests
Completed 900 requests
Completed 1000 requests
Finished 1000 requests


Server Software:        
Server Hostname:        test.abc.com
Server Port:            443
SSL/TLS Protocol:       TLSv1.2,ECDHE-RSA-AES128-GCM-SHA256,2048,128

Document Path:          /v1/test/helloword
Document Length:        21 bytes

Concurrency Level:      10
Time taken for tests:   13.639 seconds
Complete requests:      1000
Failed requests:        0
Write errors:           0
Total transferred:      221000 bytes
HTML transferred:       21000 bytes
Requests per second:    73.32 [#/sec] (mean)
Time per request:       136.389 [ms] (mean)
Time per request:       13.639 [ms] (mean, across all concurrent requests)
Transfer rate:          15.82 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:       12  117 286.8     22    1674
Processing:     4   13  36.8      5     619
Waiting:        4   13  36.8      5     619
Total:         16  130 290.3     30    1680

Percentage of the requests served within a certain time (ms)
  50%     30
  66%     61
  75%     68
  80%     73
  90%    288
  95%    840
  98%   1655
  99%   1661
 100%   1680 (longest request)