作者：烧鸡太子爷
来源：恒生LIGHT云社区
简介
今年公司开发者大会是线上的形式，按照惯例，为了服务的保障，需要对整个系统的性能做一个评估，临时抱佛脚，比较常用的工具有jmeter和Apache Bench，最终在两者之间选择了Apache Bench(简称ab)，也就针对ab工具做了一些总结。
AB简介
打开官网可以看到下面一段话：
ab is a tool for benchmarking your Apache Hypertext Transfer Protocol (HTTP) server. It is designed to give you an impression
of how your current Apache installation performs. This especially shows you how many requests per second your Apache installation
is capable of serving.ApacheBench 是 Apache 服务器自带的一个web压力测试工具，简称ab。ab又是一个行工具，对发起负载的本机要求很低，根据ab 可以创建很多的并发访问线程，模拟多个访问者同时对某一URL地址进行访问，因此可以用来测试目标服务器的负载压力。总的来说ab工具小巧简单，上手学习较快，可以提供需要的基本性能指标，但是没有图形化结果，不能监控。
jmeter和ab的比较
这个网上有很多的介绍，收集找了一位大神的总结（具体的不多说，大家可以自行百度）
1、jmeter是一次完整的请求和返回， 而AB只是发出去请求，并不对返回做处理，只是请求发送成功或者失败。 所以从准确性来说，Jmeter更准确，而AB速度更快，可以用最少的机器资源产生更多的访问请求；
2、Jmeter本身支持断言、可变参数和CSV数据集的输入，能设定更加灵活多变的的测试场景，而AB则不支持（暂时没想到）；
3、Jmeter可以提供更加详细的统计结果数据，比如接口错误信息、单线程的请求时间等，而AB则不支持；
4、Jmeter不支持精确时间的压测，比如压测10分钟，但是AB支持；
5、Jmeter支持分布式的压测集群，且支持函数，AB不支持；
6、软件自身耗费资源：Jmeter由于比较重，且统计了很多结果数据，比AB耗时耗费资源多，AB属于超轻量级，在开发测试过程中十分适合做单接口压测。
因为本次只针对单个接口做测试，手上刚好有空闲的linux机器，综合考虑就选择了AB，废话不多说，下面就进行AB的使用做一些讲解。
AB的使用
官网针对ab的使用做了很详细的介绍，我们可以去查看官网地址：
https://httpd.apache.org/docs...
下面做了一些节抄，英文比较简单，就不做翻译了。
ab参数
ab [ -A auth-username:password ] [ -b windowsize ] [ -B local-address ] [ -c concurrency ] [ -C cookie-name=value ] [ -d ]
[ -e csv-file ] [ -E client-certificate file ] [ -f protocol ] [ -g gnuplot-file ] [ -h ] [ -H custom-header ] [ -i ] [ -k ]
[ -l ] [ -m HTTP-method ] [ -n requests ] [ -p POST-file ] [ -P proxy-auth-username:password ] [ -q ] [ -r ] [ -s timeout ]
[ -S ] [ -t timelimit ] [ -T content-type ] [ -u PUT-file ] [ -v verbosity] [ -V ] [ -w ] [ -x -attributes ]
[ -X proxy[:port] ] [ -y -attributes ] [ -z -attributes ] [ -Z ciphersuite ] [http[s]://]hostname[:port]/path
参数说明
- -A auth-username:password
Supply BASIC Authentication credentials to the server. The username and password are separated by a single : and sent on the wire base64 encoded. The string is sent regardless of whether the server needs it (i.e., has sent an 401 authentication needed).
- -b windowsize
Size of TCP send/receive buffer, in bytes.
- -B local-address
Address to bind to when making outgoing connections.
- -c concurrency
Number of multiple requests to perform at a time. Default is one request at a time.
- -C cookie-name=value
Add a Cookie: line to the request. The argument is typically in the form of a name=value pair. This field is repeatable.
- -d
Do not display the "percentage served within XX [ms] table". (legacy support).
- -e csv-file
Write a Comma separated value (CSV) file which contains for each percentage (from 1% to 100%) the time (in milliseconds) it took to serve that percentage of the requests. This is usually more useful than the 'gnuplot' file; as the results are already 'binned'.
- -E client-certificate-file
When connecting to an SSL website, use the provided client certificate in PEM format to authenticate with the server. The file is expected to contain the client certificate, followed by intermediate certificates, followed by the private key. Available in 2.4.36 and later.
- -f protocol
Specify SSL/TLS protocol (SSL2, SSL3, TLS1, TLS1.1, TLS1.2, or ALL). TLS1.1 and TLS1.2 support available in 2.4.4 and later.
- -g gnuplot-file
Write all measured values out as a 'gnuplot' or TSV (Tab separate values) file. This file can easily be imported into packages like Gnuplot, IDL, Mathematica, Igor or even Excel. The labels are on the first line of the file.
- -h
Display usage information.
- -H custom-header
Append extra headers to the request. The argument is typically in the form of a valid header line, containing a colon-separated field-value pair (i.e., "Accept-Encoding: zip/zop;8bit").
- -i
Do HEAD requests instead of GET.
- -k
Enable the HTTP KeepAlive feature, i.e., perform multiple requests within one HTTP session. Default is no KeepAlive.
- -l
Do not report errors if the length of the responses is not constant. This can be useful for dynamic pages. Available in 2.4.7 and later.
- -m HTTP-method
Custom HTTP method for the requests. Available in 2.4.10 and later.
- -n requests
Number of requests to perform for the benchmarking session. The default is to just perform a single request which usually leads to non-representative benchmarking results.
- -p POST-file
File containing data to POST. Remember to also set -T.
- -P proxy-auth-username:password
Supply BASIC Authentication credentials to a proxy en-route. The username and password are separated by a single : and sent on the wire base64 encoded. The string is sent regardless of whether the proxy needs it (i.e., has sent an 407 proxy authentication needed).
- -q
When processing more than 150 requests, ab outputs a progress count on stderr every 10% or 100 requests or so. The -q flag will suppress these messages.
- -r
Don't exit on socket receive errors.
- -s timeout
Maximum number of seconds to wait before the socket times out. Default is 30 seconds. Available in 2.4.4 and later.
- -S
Do not display the median and standard deviation values, nor display the warning/error messages when the average and median are more than one or two times the standard deviation apart. And default to the min/avg/max values. (legacy support).
- -t timelimit
Maximum number of seconds to spend for benchmarking. This implies a -n 50000 internally. Use this to benchmark the server within a fixed total amount of time. Per default there is no timelimit.
- -T content-type
Content-type header to use for POST/PUT data, eg. application/x-www-form-urlencoded. Default is text/plain.
- -u PUT-file
File containing data to PUT. Remember to also set -T.
- -v verbosity
Set verbosity level - 4 and above prints information on headers, 3 and above prints response codes (404, 200, etc.), 2 and above prints warnings and info.
- -V
Display version number and exit.
- -w
Print out results in HTML tables. Default table is two columns wide, with a white background.
- -x -attributes
String to use as attributes for table. Attributes are inserted table here.
- -X proxy[:port]
Use a proxy server for the requests.
- -y -attributes
String to use as attributes for tr.
- -z -attributes
String to use as attributes for tb
- -Z ciphersuite
Specify SSL/TLS cipher suite (See openssl ciphers)
参数说明
Server Software
The value, if any, returned in the server HTTP header of the first successful response. This includes all characters in the header from beginning to the point a character with decimal value of 32 (most notably: a space or CR/LF) is detected.
Server Hostname
The DNS or IP address given on the command line
Server Port
The port to which ab is connecting. If no port is given on the command line, this will default to 80 for http and 443 for https.
SSL/TLS Protocol
The protocol parameters negotiated between the client and server. This will only be printed if SSL is used.
Document Path
The request URI parsed from the command line string.
Document Length
This is the size in bytes of the first successfully returned document. If the document length changes during testing, the response is considered an error.
Concurrency Level
The number of concurrent clients used during the test
Time taken for tests
This is the time taken from the moment the first socket connection is created to the moment the last response is received
Complete requests
The number of successful responses received
Failed requests
The number of requests that were considered a failure. If the number is greater than zero, another line will be printed showing the number of requests that failed due to connecting, reading, incorrect content length, or exceptions.
Write errors
The number of errors that failed during write (broken pipe).
Non-2xx responses
The number of responses that were not in the 200 series of response codes. If all responses were 200, this field is not printed.
Keep-Alive requests
The number of connections that resulted in Keep-Alive requests
Total body sent
If configured to send data as part of the test, this is the total number of bytes sent during the tests. This field is omitted if the test did not include a body to send.
Total transferred
The total number of bytes received from the server. This number is essentially the number of bytes sent over the wire.
HTML transferred
The total number of document bytes received from the server. This number excludes bytes received in HTTP headers
Requests per second
This is the number of requests per second. This value is the result of dividing the number of requests by the total time taken
Time per request
The average time spent per request. The first value is calculated with the formula concurrency timetaken 1000 / done while the second value is calculated with the formula timetaken * 1000 / done
Transfer rate
The rate of transfer as calculated by the formula totalread / 1024 / timetaken
举例
从上面可以看到ab支持的参数很多，但其实我们一般来说只有-n（发送的请求总数）和 -c（请求的并发线程数）的参数是必要的。
从图上的列子我们可以看出，本次是启动了200个线程并发，总共跑了2000次（为了避免泄露信息安全，对接口做了隐私处理）。
结果我们观察到
Requests for second为722.77,即每秒钟处理722.77个请求；
Time per request为276.714,即请求的平均耗时为276.714ms；
另外还可以 99线，98线，95线等的耗时指标；
特别要注意，NON-2xx responses 为2000，而请求总共2000，则表示2000个请求返回的全部都是非2000，需要考虑请求返回是否都是错误的；
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