CentOS 8 ab 安装与命令参数详解

目标：在 CentOS 8 上安装 Apache HTTP 服务器工具包 httpd-tools 自带的 HTTP 压测工具 ab（ApacheBench 2.3），并逐参数实测压测命令的输入与输出，涵盖 URL 目标、-n、-c、-t、-k、-q、-v、-H、-T、-p、-u、-C、-r、-s、-i、-w、-e 等参数，以及在线/离线安装与依赖处理。本文命令与输出均为 CentOS 8（ab 2.3，包 httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64）对目标站 http://172.28.0.5:8080/ 实测回显。

一、环境信息

操作系统：CentOS 8
ab 版本：ApacheBench Version 2.3（<$Revision: 1843412 $>）
安装包：httpd-tools 2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64（提供 ab 等 HTTP 工具）
压测客户端主机：本机，网卡 eth0，IP 172.28.0.3/16
目标站点：172.28.0.5:8080（HTTP 服务，供压测）
目标服务类型：Python http.server（SimpleHTTP，Python 3.6.8）
测试文档：/index.html（19 字节）、/file2m.bin（2 MiB）
工作目录：/opt/data/ab/

二、工具概述

ab（ApacheBench）是随 Apache HTTP Server 工具包一同安装的 HTTP 压测工具，用于模拟多并发客户端向目标 URL 发起请求，输出吞吐量、平均/峰值响应时间、连接耗时分布与完成的请求百分比，是评估 Web 服务性能的轻量命令行工具。它的单机高并发能力有限，更适合功能对比与粗略压测；生产级高并发建议配合 wrk/hey 等多进程工具。本文针对 CentOS 8 上的 ab 2.3 实测。

三、安装

3.1 在线安装（dnf/yum）

sudo dnf install -y httpd-tools
# 或
sudo yum install -y httpd-tools

💡 CentOS 8 上 ab 由 httpd-tools 包提供（对应 Ubuntu 的 apache2-utils），装完即得 ab 命令。

安装后验证版本与软件包状态：

ab -V

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

rpm -q httpd-tools

httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64

💡 ab -V 显示版本号与版权行（Version 2.3 + $Revision），不显示编译参数；调试/详细请求信息请使用 -v 而不是 -V。

3.2 离线安装（rpm 包）

在有网络的 CentOS 8 机器上先用 dnf 下载 rpm 包（dnf download 由 dnf-plugins-core 提供）：

sudo dnf install -y dnf-plugins-core
cd /opt/data/ab/offline
dnf download httpd-tools

httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac 226 kB/s | 106 kB     00:00

ls -la /opt/data/ab/offline/*.rpm

-rw-r--r-- 1 root root 108519 Oct  9 04:36 /opt/data/ab/offline/httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64.rpm

将 rpm 拷贝到离线机器后，推荐用 dnf install 本地包路径安装（会自动从可用仓库解析 libapr 等依赖）：

sudo dnf install -y /opt/data/ab/offline/httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64.rpm

  apr-util-1.6.1-6.el8.x86_64
  apr-util-bdb-1.6.1-6.el8.x86_64
  apr-util-openssl-1.6.1-6.el8.x86_64
  httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64

⚠️ 不要直接用 rpm -ivh 装 httpd-tools 离线包：实测 rpm -ivh httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64.rpm 会因缺少 libapr-1.so.0()(64bit)、libaprutil-1.so.0()(64bit) 报依赖错误直接失败。正确做法是用 dnf install ./httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64.rpm（本地路径 + ./），由 dnf 自动把 apr/apr-util 一并解析安装；完全无网络的内网机器需把 apr、apr-util 的 rpm 也一并离线下载后同目录安装。

安装后验证：

ab -V 2>&1 | head -1
rpm -q httpd-tools

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64

四、命令实测

压测目标均为 http://172.28.0.5:8080/。/index.html 为 19 字节小页面（测吞吐/并发），/file2m.bin 为 2 MiB 大文件（测传输速率）。ab 多请求时会在 STDERR 滚动 Completed 100 requests 进度行，为使输出可读，以下对较长实测量已略去中间进度行，仅保留完整汇总段，所有字段均来自真实回显。

4.1 URL 目标与基本压测 —— `ab -n 1000 -c 50 http://172.28.0.5:8080/index.html`

用途：对指定 URL 发起 1000 次请求、并发 50 的基准压测，是最常用的入门命令。

参数说明：URL 必须带 http://（或 https://）；-n requests 总请求数；-c concurrency 并发数（同时发起的请求数）。

ab -n 1000 -c 50 http://172.28.0.5:8080/index.html

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient)
Finished 1000 requests


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /index.html
Document Length:        19 bytes

Concurrency Level:      50
Time taken for tests:   0.376 seconds
Complete requests:      1000
Failed requests:        0
Total transferred:      203000 bytes
HTML transferred:       19000 bytes
Requests per second:    2661.41 [#/sec] (mean)
Time per request:       18.787 [ms] (mean)
Time per request:       0.376 [ms] (mean, across all concurrent requests)
Transfer rate:          527.60 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.3      0       3
Processing:     0    2   0.9      2      11
Waiting:        0    2   0.9      2      11
Total:          0    2   1.1      2      14

Percentage of the requests served within a certain time (ms)
  50%      2
  66%      2
  75%      2
  80%      3
  90%      3
  95%      4
  98%      4
  99%      6
 100%     14 (longest request)

解读：Concurrency Level=50、Complete requests=1000、Failed requests=0 表示全部成功；吞吐 Requests per second=2661.41 请求/秒；两行 Time per request 分别是在并发下的平均耗时（18.787ms）和按单请求均摊的耗时（0.376ms）；Connection Times 给出连接/处理/等待/总耗时统计；Percentage... 是响应时间分布，如 99% 请求在 6ms 内完成。

4.2 按时长压测 —— `ab -t 5 -c 10 http://172.28.0.5:8080/index.html`

用途：以固定时长（而非固定请求数）压测，适合连续吞吐观察。

参数说明：-t timelimit 压测最长时间（秒）；使用 -t 时系统自动把请求数设为 50000 兜底（帮助原文：This implies -n 50000），到点即结束。

ab -t 5 -c 10 http://172.28.0.5:8080/index.html

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient)
Finished 16243 requests


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /index.html
Document Length:        19 bytes

Concurrency Level:      10
Time taken for tests:   5.000 seconds
Complete requests:      16243
Failed requests:        0
Total transferred:      3298141 bytes
HTML transferred:       308693 bytes
Requests per second:    3248.45 [#/sec] (mean)
Time per request:       3.078 [ms] (mean)
Time per request:       0.308 [ms] (mean, across all concurrent requests)
Transfer rate:          644.14 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    1  33.6      0    2086
Processing:     0    2   7.5      2     826
Waiting:        0    2   7.4      2     826
Total:          0    3  37.0      2    2088

Percentage of the requests served within a certain time (ms)
  50%      2
  66%      2
  75%      2
  80%      2
  90%      3
  95%      3
  98%      3
  99%      4
 100%   2088 (longest request)

解读：Time taken for tests=5.000 秒即到时长自动停止；5 秒内完成 16243 次请求，Requests per second=3248.45。Finished 16243 requests 说明本次到点结束而非跑满 50000 兜底数。

4.3 开启 Keep-Alive 复用连接 —— `ab -k -n 2000 -c 20 http://172.28.0.5:8080/index.html`

用途：复用已建立的 TCP 连接（HTTP Keep-Alive），减少建连开销，对比连接复用对吞吐的影响。

参数说明：-k 使用 HTTP Keep-Alive（帮助原文：Use HTTP KeepAlive feature）。

ab -k -n 2000 -c 20 http://172.28.0.5:8080/index.html

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient)
Finished 2000 requests


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /index.html
Document Length:        19 bytes

Concurrency Level:      20
Time taken for tests:   0.585 seconds
Complete requests:      2000
Failed requests:        0
Keep-Alive requests:    0
Total transferred:      406000 bytes
HTML transferred:       38000 bytes
Requests per second:    3418.93 [#/sec] (mean)
Time per request:       5.850 [ms] (mean)
Time per request:       0.292 [ms] (mean, across all concurrent requests)
Transfer rate:          677.78 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       2
Processing:     0    2   0.4      2       5
Waiting:        0    2   0.4      2       5
Total:          0    2   0.4      2       5

Percentage of the requests served within a certain time (ms)
  50%      2
  66%      2
  75%      2
  80%      2
  90%      2
  95%      2
  98%      3
  99%      3
 100%      5 (longest request)

解读：Keep-Alive requests=0 说明目标 Python SimpleHTTP/0.6 服务端收到含 Keep-Alive 的请求后未对该 ab 连接标记为复用（Python http.server 以 HTTP/1.0 Connection: close 响应），因此实际仍未复用连接；吞吐与 4.1 同并发量级相当，佐证未真正复用。请以目标服务端是否支持 Keep-Alive 为准。

4.4 静默模式（大于 150 请求不再打进度） —— `ab -q -n 3000 -c 30 http://172.28.0.5:8080/index.html`

用途：-q 在请求数超过 150 时取消逐 100 行进度输出，只打印汇总，适合脚本化落盘。

参数说明：-q 帮助原文：Do not show progress when doing more than 150 requests。

ab -q -n 3000 -c 30 http://172.28.0.5:8080/index.html

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient).....done


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /index.html
Document Length:        19 bytes

Concurrency Level:      30
Time taken for tests:   0.874 seconds
Complete requests:      3000
Failed requests:        0
Total transferred:      609000 bytes
HTML transferred:       57000 bytes
Requests per second:    3433.08 [#/sec] (mean)
Time per request:       8.739 [ms] (mean)
Time per request:       0.291 [ms] (mean, across all concurrent requests)
Transfer rate:          680.58 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       3
Processing:     0    2   0.4      2       4
Waiting:        0    2   0.4      1       4
Total:          0    2   0.4      2       4
ERROR: The median and mean for the waiting time are more than twice the standard
       deviation apart. These results are NOT reliable.

Percentage of the requests served within a certain time (ms)
  50%      2
  66%      2
  75%      2
  80%      2
  90%      2
  95%      3
  98%      3
  99%      3
 100%      4 (longest request)

解读：加上 -q 后 3000 个请求中间不再输出 Completed x00 requests 进度，只在开始时打印 ...done，随后直接进入汇总。末尾 ERROR: ...NOT reliable 是 ab 的统计提示而非执行失败：本机响应毫秒级、均值与中位数偏差超两倍标准差所致，详情见常见问题。

4.5 详细级别——打印请求头与响应头 —— `ab -v 4 -n 2 -c 1 -H "X-Auth: token123" -C "session=pmm" http://172.28.0.5:8080/index.html`

用途：-v 输出排障级别（1-4）详细信息，-v 4 打印逐请求的请求头发送与响应头接收，便于核对自定义头、Cookie 是否生效。

参数说明：-v verbosity 帮助原文：How much troubleshooting info to print（0 关闭、1 报告、2-3 基本信息、4 请求级详细）；-H attribute 添加任意请求头（帮助原文：Add Arbitrary header line, eg. 'Accept-Encoding: gzip'，可重复）；-C attribute 添加 Cookie（帮助原文：Add cookie, eg. 'Apache=1234'，可重复）。

ab -v 4 -n 2 -c 1 -H "X-Auth: token123" -C "session=pmm" http://172.28.0.5:8080/index.html

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient)...INFO: GET header ==
---
GET /index.html HTTP/1.0
Cookie: session=pmm
X-Auth: token123
Host: 172.28.0.5:8080
User-Agent: ApacheBench/2.3
Accept: */*


---
LOG: header received:
HTTP/1.0 200 OK
Server: SimpleHTTP/0.6 Python/3.6.8
Date: Fri, 09 Oct 2026 04:36:16 GMT
Content-type: text/html
Content-Length: 19
Last-Modified: Fri, 09 Oct 2026 04:27:10 GMT


LOG: Response code = 200
LOG: header received:
HTTP/1.0 200 OK
Server: SimpleHTTP/0.6 Python/3.6.8
Date: Fri, 09 Oct 2026 04:36:16 GMT
Content-type: text/html
Content-Length: 19
Last-Modified: Fri, 09 Oct 2026 04:27:10 GMT


LOG: Response code = 200
..done


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /index.html
Document Length:        19 bytes

Concurrency Level:      1
Time taken for tests:   0.002 seconds
Complete requests:      2
Failed requests:        0
Total transferred:      406 bytes
HTML transferred:       38 bytes
Requests per second:    1150.75 [#/sec] (mean)
Time per request:       0.869 [ms] (mean)
Time per request:       0.869 [ms] (mean, across all concurrent requests)
Transfer rate:          228.13 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       0
Processing:     1    1   0.1      1       1
Waiting:        1    1   0.1      1       1
Total:          1    1   0.1      1       1

Percentage of the requests served within a certain time (ms)
  50%      1
  66%      1
  75%      1
  80%      1
  90%      1
  95%      1
  98%      1
  99%      1
 100%      1 (longest request)

解读：INFO: GET header == 后列出的请求头中可见 Cookie: session=pmm（来自 -C）与 X-Auth: token123（来自 -H），均插入在 Host 等常规头之前；LOG: header received: 后是目标服务端逐请求返回的响应头（HTTP/1.0 200 OK、Server: SimpleHTTP/0.6 Python/3.6.8 等）。-v 4 只作少量请求（-n 2 -c 1）调试用，量大时不要这么用。

4.6 自定义请求头 —— 单一用途演示 `ab -n 20 -c 2 -H "X-Test-Header: ab-demo" http://172.28.0.5:8080/index.html`

用途：单发一个自定义头即可用于功能验证（详见 4.5 的多头场景），此处展示常规汇总回显。

参数说明：-H "Header: value" 任意请求头，可多次重复以追加。

ab -n 20 -c 2 -H "X-Test-Header: ab-demo" http://172.28.0.5:8080/index.html

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient).....done


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /index.html
Document Length:        19 bytes

Concurrency Level:      2
Time taken for tests:   0.009 seconds
Complete requests:      20
Failed requests:        0
Total transferred:      4060 bytes
HTML transferred:       380 bytes
Requests per second:    2315.89 [#/sec] (mean)
Time per request:       0.864 [ms] (mean)
Time per request:       0.432 [ms] (mean, across all concurrent requests)
Transfer rate:          459.11 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       0
Processing:     0    1   0.1      1       1
Waiting:        0    1   0.2      1       1
Total:          0    1   0.2      1       1

Percentage of the requests served within a certain time (ms)
  50%      1
  66%      1
  75%      1
  80%      1
  90%      1
  95%      1
  98%      1
  99%      1
 100%      1 (longest request)

解读：小并发（-c 2）+ 少量请求（-n 20）时吞吐 2315.89 请求/秒，Total transferred 4060 字节 = 19 字节 × 20 请求 + 响应头开销。-H 对 ab 汇总无影响，只改变实际发出的请求头。

4.7 发送 POST 数据 —— `-p` 与 `-T`（对不支持 POST 的目标会返回非 2xx）

用途：-p postfile 指定 POST 数据文件（帮助原文：File containing data to POST. Remember also to set -T）；-T content-type 指定请求体的 Content-Type（帮助原文：Default is 'text/plain'）。

参数说明：POST 需同时给出数据文件与 -T；ab 会自动发出 POST /path 请求并在汇总段显示 Total body sent。

实测数据文件：

cat /opt/data/ab/post.txt

POSTDATA_AB_TEST

ab -n 20 -c 2 -p /opt/data/ab/post.txt -T "application/x-www-form-urlencoded" http://172.28.0.5:8080/

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient).....done


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /
Document Length:        497 bytes

Concurrency Level:      2
Time taken for tests:   0.007 seconds
Complete requests:      20
Failed requests:        0
Non-2xx responses:      20
Total transferred:      13880 bytes
Total body sent:        3380
HTML transferred:       9940 bytes
Requests per second:    2987.30 [#/sec] (mean)
Time per request:       0.669 [ms] (mean)
Time per request:       0.335 [ms] (mean, across all concurrent requests)
Transfer rate:          2024.60 [Kbytes/sec] received
                        493.02 kb/s sent
                        2517.62 kb/s total

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       0
Processing:     0    1   0.2      1       1
Waiting:        0    0   0.2      0       1
Total:          0    1   0.2      1       1

Percentage of the requests served within a certain time (ms)
  50%      1
  66%      1
  75%      1
  80%      1
  90%      1
  95%      1
  98%      1
  99%      1
 100%      1 (longest request)

解读：目标为 Python SimpleHTTP/0.6，不支持 POST（返回 501/405），故 Non-2xx responses=20、Document Length=497 为错误页字节数；Total body sent=3380 字节即 20 次请求体（16 字节 × 20 = 320）加 HTTP 头开销。解读要点：Failed requests=0 不表示成功——ab 把「HTTP 层面已返回、但非 2xx」计入 Non-2xx responses，压测时务必要看 Non-2xx responses 是否为 0。

4.8 发送 PUT 数据 —— `-u` 与 `-T`

用途：-u putfile 指定 PUT 数据文件（帮助原文：File containing data to PUT. Remember also to set -T），用法与 -p 同理。

cat /opt/data/ab/put.txt

PUTDATA_AB_TEST

ab -n 20 -c 2 -u /opt/data/ab/put.txt -T "text/plain" http://172.28.0.5:8080/

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient).....done


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /
Document Length:        496 bytes

Concurrency Level:      2
Time taken for tests:   0.009 seconds
Complete requests:      20
Failed requests:        0
Non-2xx responses:      20
Total transferred:      13840 bytes
Total body sent:        2880
HTML transferred:       9920 bytes
Requests per second:    2322.88 [#/sec] (mean)
Time per request:       0.861 [ms] (mean)
Time per request:       0.430 [ms] (mean, across all concurrent requests)
Transfer rate:          1569.76 [Kbytes/sec] received
                        326.66 kb/s sent
                        1896.41 kb/s total

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       1
Processing:     0    1   0.2      1       1
Waiting:        0    1   0.2      1       1
Total:          0    1   0.3      1       1

Percentage of the requests served within a certain time (ms)
  50%      1
  66%      1
  75%      1
  80%      1
  90%      1
  95%      1
  98%      1
  99%      1
 100%      1 (longest request)

解读：与 4.7 相同，Python SimpleHTTP/0.6 不支持 PUT，返回非 2xx；Total body sent=2880 字节（15 字节 × 20 次 + 头开销）。目标若是支持 PUT 的接口（如 Tomcat/OpenAPI 服务），此输出中 Non-2xx responses 应为 0。

4.9 Cookie —— `-C "CookieName=value"`

用途：-C 模拟携带 Cookie（帮助原文：Add cookie, eg. 'Apache=1234'），可重复指定多个 Cookie 键值对；如需完整 Cookie: a=1; b=2 头也可用 -H "Cookie: a=1; b=2"。

参数说明：-C "sessionid=ab123" 即发送 Cookie: sessionid=ab123；验证发送是否生效见 4.5 的 -v 4 回显。

ab -n 20 -c 2 -C "sessionid=ab123" http://172.28.0.5:8080/index.html

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient).....done


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /index.html
Document Length:        19 bytes

Concurrency Level:      2
Time taken for tests:   0.008 seconds
Complete requests:      20
Failed requests:        0
Total transferred:      4060 bytes
HTML transferred:       380 bytes
Requests per second:    2511.62 [#/sec] (mean)
Time per request:       0.796 [ms] (mean)
Time per request:       0.398 [ms] (mean, across all concurrent requests)
Transfer rate:          497.91 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       0
Processing:     0    1   0.1      1       1
Waiting:        0    1   0.1      1       1
Total:          1    1   0.2      1       1

Percentage of the requests served within a certain time (ms)
  50%      1
  66%      1
  75%      1
  80%      1
  90%      1
  95%      1
  98%      1
  99%      1
 100%      1 (longest request)

解读：-C 对小页面基准性能无影响，汇总字段与普通 GET 一致；其效果体现在实际请求头里的 Cookie: 行（见 4.5 回显）。

4.10 出错继续（socket 接收错误不退出） —— `-r`（对非监听端口）

用途：-r 帮助原文：Don't exit on socket receive errors。当目标不可达/中途断开时，默认 ab 收到 apr_socket_recv 错误即退出；加 -r 则继续跑完剩余请求。

先看默认行为（对非监听端口 9999，不加 -r）：

ab -n 5 -c 2 http://172.28.0.5:9999/

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient)...apr_socket_recv: Connection refused (111)

进程退出码为 111：

ab -n 5 -c 2 http://172.28.0.5:9999/ >/dev/null 2>&1; echo "RC=$?"

RC=111

加 -r 后继续完成：

ab -r -n 10 -c 2 http://172.28.0.5:9999/

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient).....done


Server Software:
Server Hostname:        172.28.0.5
Server Port:            9999

Document Path:          /
Document Length:        0 bytes

Concurrency Level:      2
Time taken for tests:   0.000 seconds
Complete requests:      10
Failed requests:        15
   (Connect: 0, Receive: 10, Length: 0, Exceptions: 5)
Total transferred:      0 bytes
HTML transferred:       0 bytes
Requests per second:    29239.77 [#/sec] (mean)
Time per request:       0.068 [ms] (mean)
Time per request:       0.034 [ms] (mean, across all concurrent requests)
Transfer rate:          0.00 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.0      0       0
Processing:     0    0   0.0      0       0
Waiting:        0    0   0.0      0       0
Total:          0    0   0.0      0       0

Percentage of the requests served within a certain time (ms)
  50%      0
  66%      0
  75%      0
  80%      0
  90%      0
  95%      0
  98%      0
  99%      0
 100%      0 (longest request)

解读：加 -r 后 ab 不再因连接被拒而中途退出，Complete requests=10 跑完，但 Failed requests=15（含 Receive 10、Exceptions 5），Total transferred=0。Failed requests 大于 Complete requests 说明有请求在建立连接后接收失败被计错——这是 -r 场景下的典型正常表现，压测里若端口可达但出现大量 failed 需排查服务与网络。

4.11 超时控制 —— `-s 1`（单请求等待超时）

用途：-s timeout 设置单次请求的最大等待时间（秒），默认 30 秒（见 ab -h，Default is 30 seconds）。对响应慢的目标调低可缩短整体压测时长；目标响应正常时 -s 1 不影响结果。

ab -s 1 -n 500 -c 10 http://172.28.0.5:8080/index.html

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient)
Finished 500 requests


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /index.html
Document Length:        19 bytes

Concurrency Level:      10
Time taken for tests:   0.177 seconds
Complete requests:      500
Failed requests:        0
Total transferred:      101500 bytes
HTML transferred:       9500 bytes
Requests per second:    2816.98 [#/sec] (mean)
Time per request:       3.550 [ms] (mean)
Time per request:       0.355 [ms] (mean, across all concurrent requests)
Transfer rate:          558.44 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       2
Processing:     0    2   0.8      2       6
Waiting:        0    2   0.8      2       6
Total:          0    2   0.8      2       6

Percentage of the requests served within a certain time (ms)
  50%      2
  66%      2
  75%      2
  80%      3
  90%      3
  95%      3
  98%      4
  99%      5
 100%      6 (longest request)

解读：目标响应约 0~6ms，远低于 1s 超时，故 Failed requests=0、进程正常跑完。若目标无响应超过 -s 指定的秒数，ab 会把这些请求计为超时(failed)，并可能整体提前结束。

4.12 使用 HEAD 请求 —— `-i`

用途：-i 帮助原文：Use HEAD instead of GET，只取响应头、不取响应体，常用于 HEAD 接口联通性压测。

ab -i -n 50 -c 5 http://172.28.0.5:8080/index.html

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient).....done


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /index.html
Document Length:        0 bytes

Concurrency Level:      5
Time taken for tests:   0.013 seconds
Complete requests:      50
Failed requests:        0
Total transferred:      9200 bytes
HTML transferred:       0 bytes
Requests per second:    3841.13 [#/sec] (mean)
Time per request:       1.302 [ms] (mean)
Time per request:       0.260 [ms] (mean, across all concurrent requests)
Transfer rate:          690.20 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       0
Processing:     0    1   0.4      1       2
Waiting:        0    1   0.4      1       2
Total:          0    1   0.3      1       2

Percentage of the requests served within a certain time (ms)
  50%      1
  66%      1
  75%      1
  80%      1
  90%      2
  95%      2
  98%      2
  99%      2
 100%      2 (longest request)

解读：Document Path 仍是 /index.html，但 Document Length=0、HTML transferred=0 bytes，只传了响应头；Total transferred=9200 字节为 50 次响应头累计。

4.13 大文件压测（传输速率） —— `ab -n 200 -c 20 http://172.28.0.5:8080/file2m.bin`

用途：以 2 MiB 文件为目标，观察吞吐与 Transfer rate（有效传输速率），用于带宽/传输评估。

ab -n 200 -c 20 http://172.28.0.5:8080/file2m.bin

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

Benchmarking 172.28.0.5 (be patient)
Finished 200 requests


Server Software:        SimpleHTTP/0.6
Server Hostname:        172.28.0.5
Server Port:            8080

Document Path:          /file2m.bin
Document Length:        2097152 bytes

Concurrency Level:      20
Time taken for tests:   0.844 seconds
Complete requests:      200
Failed requests:        0
Total transferred:      419471200 bytes
HTML transferred:       419430400 bytes
Requests per second:    236.94 [#/sec] (mean)
Time per request:       84.411 [ms] (mean)
Time per request:       4.221 [ms] (mean, across all concurrent requests)
Transfer rate:          485294.32 [Kbytes/sec] received

Connection Times (ms)
              min  mean[+/-sd] median   max
Connect:        0    0   0.1      0       1
Processing:     9   25   6.6     23      52
Waiting:        0   21   6.1     20      45
Total:          9   25   6.6     23      52

Percentage of the requests served within a certain time (ms)
  50%     23
  66%     25
  75%     26
  80%     27
  90%     32
  95%     45
  98%     47
  99%     52
 100%     52 (longest request)

解读：大文件下 Document Length=2097152（2MiB）、Transfer rate=485294.32 Kbytes/s（约 473MB/s）反映内网传输能力强；单请求 Time per request（mean）=84.411ms 主要花在传体上，故小页面吞吐高、大文件吞吐低但传输速率高。压测大文件主要看 Transfer rate 与 Document Length，小页面主要看 Requests per second。

4.14 输出到 CSV 文件 —— `-e filename`（百分比-耗时表）

用途：-e filename 帮助原文：Output CSV file with percentages served，把百分位-响应时间关系写为 CSV，便于绘图/归档。

ab -n 100 -c 5 -e /tmp/ab-percent.csv http://172.28.0.5:8080/index.html
cat /tmp/ab-percent.csv

Percentage served,Time in ms
0,0.705
1,0.764
2,0.923
3,1.103
4,1.133
5,1.134
10,1.208
20,1.288
30,1.336
40,1.379
50,1.417
60,1.479
70,1.539
80,1.601
90,1.694
95,1.825
98,1.895
99,1.999
100,1.999

解读：CSV 首行为表头 Percentage served,Time in ms，其后每行「百分位,毫秒」，如 50% 请求在 1.417ms 内完成、99% 在 1.999ms 内完成。可配合 -g（输出 gnuplot 格式）或用 -w（HTML 表格输出，见 4.15）。

4.15 HTML 表格输出 —— `-w`

用途：-w 帮助原文：Print out results in HTML tables，把汇总表格输出为 HTML <table>，适合贴到报告里。

ab -w -n 20 -c 2 http://172.28.0.5:8080/index.html > /tmp/ab-report.html
wc -l /tmp/ab-report.html

29 /tmp/ab-report.html

head -22 /tmp/ab-report.html

<p>
 This is ApacheBench, Version 2.3 <i>&lt;$Revision: 1843412 $&gt;</i><br>
 Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/<br>
 Licensed to The Apache Software Foundation, http://www.apache.org/<br>
</p>
<p>
..done


<table >
<tr ><th colspan=2 bgcolor=white>Server Software:</th><td colspan=2 bgcolor=white>SimpleHTTP/0.6</td></tr>
<tr ><th colspan=2 bgcolor=white>Server Hostname:</th><td colspan=2 bgcolor=white>172.28.0.5</td></tr>
<tr ><th colspan=2 bgcolor=white>Server Port:</th><td colspan=2 bgcolor=white>8080</td></tr>
<tr ><th colspan=2 bgcolor=white>Document Path:</th><td colspan=2 bgcolor=white>/index.html</td></tr>
<tr ><th colspan=2 bgcolor=white>Document Length:</th><td colspan=2 bgcolor=white>19 bytes</td></tr>
<tr ><th colspan=2 bgcolor=white>Concurrency Level:</th><td colspan=2 bgcolor=white>2</td></tr>
<tr ><th colspan=2 bgcolor=white>Time taken for tests:</th><td colspan=2 bgcolor=white>0.007 seconds</td></tr>
<tr ><th colspan=2 bgcolor=white>Complete requests:</th><td colspan=2 bgcolor=white>20</td></tr>
<tr ><th colspan=2 bgcolor=white>Failed requests:</th><td colspan=2 bgcolor=white>0</td></tr>
<tr ><th colspan=2 bgcolor=white>Total transferred:</th><td colspan=2 bgcolor=white>4060 bytes</td></tr>
</html>

解读：输出主体是一张 HTML 表格（<table >），首部把版权信息与进度输出为 <p> 段落，随后以 <tr ><th colspan=2 bgcolor=white>字段名:</th> 逐行列出服务端信息与汇总，末行 </html> 收尾；-x/-y/-z 可分别给 <table>/<tr>/<td> 注入属性，-w -i 可组合生成 HEAD 请求的 HTML 报告。

五、帮助输出

5.1 `ab -h`（帮助全文，CentOS 8 / httpd-tools 2.4.37）

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
    -l              Accept variable document length (use this for dynamic pages)
    -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.
    -m method       Method name
    -h              Display usage information (this message)
    -I              Disable TLS Server Name Indication (SNI) extension
    -Z ciphersuite  Specify SSL/TLS cipher suite (See openssl ciphers)
    -f protocol     Specify SSL/TLS protocol
                    (SSL2, TLS1, TLS1.1, TLS1.2 or ALL)
    -E certfile     Specify optional client certificate chain and private key

5.2 `ab -V`（版本行）

This is ApacheBench, Version 2.3 <$Revision: 1843412 $>
Copyright 1996 Adam Twiss, Zeus Technology Ltd, http://www.zeustech.net/
Licensed to The Apache Software Foundation, http://www.apache.org/

💡 版本标识为 Version 2.3 <$Revision: 1843412 $>；$Revision 随发行版不同而异（CentOS 8 为 1843412，Ubuntu 22.04 为 1879490），此行的存在标志 HTTP server benchmarking tool 即 ab 本体。

六、常见问题

6.1 为什么 `Failed requests` 为 0 但实际都是错误响应？

Q：压测时看到 Failed requests: 0，但服务端其实一直返回错误页面？ A：ab 把「HTTP 请求已发出并收到响应」都算作成功，Failed requests 只统计连接失败/接收异常的请求；HTTP 层面返回非 2xx（如 404、501、405）会计入 Non-2xx responses。判断成功必须同时检查 Failed requests（应为 0）与 Non-2xx responses（应为 0）。本环境 Python SimpleHTTP 不支持 POST/PUT，用 -p/-u 压测时即出现 Non-2xx responses=20 而 Failed requests=0。

6.2 目标不可达时报 `apr_socket_recv: Connection refused (111)`

Q：ab 直接以 apr_socket_recv: Connection refused (111) 退出、RC=111 是怎么回事？ A：目标端口未监听/网络不可达。默认 ab 遇到 socket 接收错误即中止（退出码 111）；需要「遇错继续」时加 -r（见 4.10），此时跑完 Complete requests、失败计入 Failed requests（Receive/Exceptions 分类）。

6.3 为什么 `Requests per second` 很小、`Time per request` 差异大？

Q：同样命令多次跑，Requests per second 波动大，且 Time per request 有差别？ A：目标为单线程 Python http.server，高并发下请求在服务端排队，吞吐会明显下降。压测时要在目标服务大致稳定的环境下取多次均值，并在同样并发档位下比较；分析需同时看 Requests per second、Connection Times（尤其 Processing/Wait）与百分位表。

6.4 输出里出现 `ERROR: The median and mean ... are more than twice the standard deviation apart. These results are NOT reliable`？

Q：汇总里多了一行 ERROR: ...NOT reliable 是失败了吗？ A：不是执行失败，而是 ab 的统计提示：当某耗时维度（如 Waiting/Processing/Total）的均值与中位数偏差超过两倍标准差时（常见于 -n/-c 较小或长尾明显），ab 认为该统计不可靠并打印提示。可增大 -n/-c、或关注百分位表而非单看均值来平滑波动。

6.5 为什么 `-t` 明明设了时长却没跑满？

Q：-t 10 但 Time taken for tests 只有几秒？ A：-t 是最长时长（max. to spend），默认 -n 50000 兜底；若请求提前全部完成（如大文件很快发完 50000 次）则提前结束。需要严格跑满时长请用较大的 -n 或不设 -n 让兜底值生效，并观察 Finished X requests。

6.6 离线安装时 `rpm -ivh` 报缺 `libapr-1.so.0` 依赖

Q：离线机器上 rpm -ivh httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64.rpm 报 libapr-1.so.0()(64bit) is needed？ A：httpd-tools 依赖 apr/apr-util 运行库，rpm -ivh 不解析依赖。改用 dnf install /opt/data/ab/offline/httpd-tools-2.4.37-39.module_el8.4.0+950+0577e6ac.1.x86_64.rpm（本地路径 + ./），让 dnf 自动解析并安装 apr、apr-util（见 3.2）；完全断网环境需把 apr、apr-util、apr-util-bdb、apr-util-openssl 等 rpm 一并离线下载后同目录安装。

七、参考链接

ApacheBench / ab 官方文档（Apache HTTP Server 工具）：https://httpd.apache.org/docs/2.4/programs/ab.html
Red Hat / CentOS 软件包 httpd-tools 信息：https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/deploying_different_types_of_servers/
Apache Benchmark（ab）开源源码：https://github.com/apache/httpd
本文素材来源：CentOS 8（ab 2.3）实测采集

CentOS 8 ab 安装与命令参数详解

CentOS 8 ab 安装与命令参数详解

一、环境信息

二、工具概述

三、安装

3.1 在线安装（dnf/yum）

3.2 离线安装（rpm 包）

四、命令实测

4.1 URL 目标与基本压测 —— ab -n 1000 -c 50 http://172.28.0.5:8080/index.html

4.2 按时长压测 —— ab -t 5 -c 10 http://172.28.0.5:8080/index.html

4.3 开启 Keep-Alive 复用连接 —— ab -k -n 2000 -c 20 http://172.28.0.5:8080/index.html

4.4 静默模式（大于 150 请求不再打进度） —— ab -q -n 3000 -c 30 http://172.28.0.5:8080/index.html

4.5 详细级别——打印请求头与响应头 —— ab -v 4 -n 2 -c 1 -H "X-Auth: token123" -C "session=pmm" http://172.28.0.5:8080/index.html

4.6 自定义请求头 —— 单一用途演示 ab -n 20 -c 2 -H "X-Test-Header: ab-demo" http://172.28.0.5:8080/index.html

4.7 发送 POST 数据 —— -p 与 -T（对不支持 POST 的目标会返回非 2xx）

4.8 发送 PUT 数据 —— -u 与 -T

4.9 Cookie —— -C "CookieName=value"

4.10 出错继续（socket 接收错误不退出） —— -r（对非监听端口）

4.11 超时控制 —— -s 1（单请求等待超时）

4.12 使用 HEAD 请求 —— -i

4.13 大文件压测（传输速率） —— ab -n 200 -c 20 http://172.28.0.5:8080/file2m.bin

4.14 输出到 CSV 文件 —— -e filename（百分比-耗时表）

4.15 HTML 表格输出 —— -w

五、帮助输出

5.1 ab -h（帮助全文，CentOS 8 / httpd-tools 2.4.37）

5.2 ab -V（版本行）

六、常见问题

6.1 为什么 Failed requests 为 0 但实际都是错误响应？

6.2 目标不可达时报 apr_socket_recv: Connection refused (111)

6.3 为什么 Requests per second 很小、Time per request 差异大？

6.4 输出里出现 ERROR: The median and mean ... are more than twice the standard deviation apart. These results are NOT reliable？

6.5 为什么 -t 明明设了时长却没跑满？

6.6 离线安装时 rpm -ivh 报缺 libapr-1.so.0 依赖

七、参考链接

4.1 URL 目标与基本压测 —— `ab -n 1000 -c 50 http://172.28.0.5:8080/index.html`

4.2 按时长压测 —— `ab -t 5 -c 10 http://172.28.0.5:8080/index.html`

4.3 开启 Keep-Alive 复用连接 —— `ab -k -n 2000 -c 20 http://172.28.0.5:8080/index.html`

4.4 静默模式（大于 150 请求不再打进度） —— `ab -q -n 3000 -c 30 http://172.28.0.5:8080/index.html`

4.5 详细级别——打印请求头与响应头 —— `ab -v 4 -n 2 -c 1 -H "X-Auth: token123" -C "session=pmm" http://172.28.0.5:8080/index.html`

4.6 自定义请求头 —— 单一用途演示 `ab -n 20 -c 2 -H "X-Test-Header: ab-demo" http://172.28.0.5:8080/index.html`

4.7 发送 POST 数据 —— `-p` 与 `-T`（对不支持 POST 的目标会返回非 2xx）

4.8 发送 PUT 数据 —— `-u` 与 `-T`

4.9 Cookie —— `-C "CookieName=value"`

4.10 出错继续（socket 接收错误不退出） —— `-r`（对非监听端口）

4.11 超时控制 —— `-s 1`（单请求等待超时）

4.12 使用 HEAD 请求 —— `-i`

4.13 大文件压测（传输速率） —— `ab -n 200 -c 20 http://172.28.0.5:8080/file2m.bin`

4.14 输出到 CSV 文件 —— `-e filename`（百分比-耗时表）

4.15 HTML 表格输出 —— `-w`

5.1 `ab -h`（帮助全文，CentOS 8 / httpd-tools 2.4.37）

5.2 `ab -V`（版本行）

6.1 为什么 `Failed requests` 为 0 但实际都是错误响应？

6.2 目标不可达时报 `apr_socket_recv: Connection refused (111)`

6.3 为什么 `Requests per second` 很小、`Time per request` 差异大？

6.4 输出里出现 `ERROR: The median and mean ... are more than twice the standard deviation apart. These results are NOT reliable`？

6.5 为什么 `-t` 明明设了时长却没跑满？

6.6 离线安装时 `rpm -ivh` 报缺 `libapr-1.so.0` 依赖