Apache服务器自定义扩展模块编写流程

灵感：
应业务的要求，我需要在Apache上扩展出自定义的功能模块，以便处理特殊请求，study了半天，终于摸透了编写Apache扩展模块编写流程。为了方便以后记忆及查询，特记录此篇

资料：
Apache API查询：https://ci.apache.org/projects/httpd/trunk/doxygen/index.html
Apache 模块说明：https://httpd.apache.org/docs/2.4/developer/modguide.html
例子1：https://www.cnblogs.com/274914765qq/p/4453315.html
例子2：http://blog.youkuaiyun.com/hqin6/article/details/6166750
例子3：https://www.cnblogs.com/baochuan/archive/2012/03/27/2418789.html

环境：
操作系统：Ubuntu 17.10 server 64bit
Apache版：Apache2
Apache API：Apache2.0 Handler
PHP版本：7.1
Apache modules目录：/usr/lib/apache2/modules
Apache 运行目录：/etc/apache2
Apache 网页目录：/var/www/html
Apache 配置文件位置：/etc/apache2/apache2.conf

Apache启停操作
Apachectl stop
apachectl start
apachectl restart
/etc/init.d/apache2 stop
/etc/init.d/apache2 start
/etc/init.d/apache2 restart

工具
apxs
没有则安装：sudo apt install apache2-dev

默认示例
在任意目录（你想放源文件的目录，通常是home/usr）使用命令：apxs -g -n hello 将会生成一个hello文件夹，并把所有文件放到里面。
hello文件夹初始内容：
Makefile
modules.mk
mod_hello.c
.deps

其中
Makefile文件：

##
##  Makefile -- Build procedure for sample hello Apache module
##  Autogenerated via ``apxs -n hello -g''.
##

builddir=.
top_srcdir=/usr/share/apache2
top_builddir=/usr/share/apache2
include /usr/share/apache2/build/special.mk

#   the used tools
APACHECTL=apachectl

#   additional defines, includes and libraries
#DEFS=-Dmy_define=my_value
#INCLUDES=-Imy/include/dir
#LIBS=-Lmy/lib/dir -lmylib

#   the default target
all: local-shared-build

#   install the shared object file into Apache 
install: install-modules-yes

#   cleanup
clean:
    -rm -f mod_hello.o mod_hello.lo mod_hello.slo mod_hello.la 

#   simple test
test: reload
    lynx -mime_header http://localhost/hello

#   install and activate shared object by reloading Apache to
#   force a reload of the shared object file
reload: install restart

#   the general Apache start/restart/stop
#   procedures
start:
    $(APACHECTL) start
restart:
    $(APACHECTL) restart
stop:
    $(APACHECTL) stop

mod_hello.c文件：

/* 
**  mod_hello.c -- Apache sample hello module
**  [Autogenerated via ``apxs -n hello -g'']
**
**  To play with this sample module first compile it into a
**  DSO file and install it into Apache's modules directory 
**  by running:
**
**    $ apxs -c -i mod_hello.c
**
**  Then activate it in Apache's apache2.conf file for instance
**  for the URL /hello in as follows:
**
**    #   apache2.conf
**    LoadModule hello_module modules/mod_hello.so
**    <Location /hello>
**    SetHandler hello
**    </Location>
**
**  Then after restarting Apache via
**
**    $ apachectl restart
**
**  you immediately can request the URL /hello and watch for the
**  output of this module. This can be achieved for instance via:
**
**    $ lynx -mime_header http://localhost/hello 
**
**  The output should be similar to the following one:
**
**    HTTP/1.1 200 OK
**    Date: Tue, 31 Mar 1998 14:42:22 GMT
**    Server: Apache/1.3.4 (Unix)
**    Connection: close
**    Content-Type: text/html
**  
**    The sample page from mod_hello.c
*/ 

#include "httpd.h"
#include "http_config.h"
#include "http_protocol.h"
#include "ap_config.h"

/* The sample content handler */
static int hello_handler(request_rec *r)
{
    if (strcmp(r->handler, "hello")) {
        return DECLINED;
    }
    r->content_type = "text/html";      

    if (!r->header_only)
        ap_rputs("The sample page from mod_hello.c\n", r);
    return OK;
}

static void hello_register_hooks(apr_pool_t *p)
{
    ap_hook_handler(hello_handler, NULL, NULL, APR_HOOK_MIDDLE);
}

/* Dispatch list for API hooks */
module AP_MODULE_DECLARE_DATA hello_module = {
    STANDARD20_MODULE_STUFF, 
    NULL,                  /* create per-dir    config structures */
    NULL,                  /* merge  per-dir    config structures */
    NULL,                  /* create per-server config structures */
    NULL,                  /* merge  per-server config structures */
    NULL,                  /* table of config file commands       */
    hello_register_hooks  /* register hooks                      */
};

modules.mk文件：

mod_hello.la: mod_hello.slo
    $(SH_LINK) -rpath $(libexecdir) -module -avoid-version  mod_hello.lo
DISTCLEAN_TARGETS = modules.mk
shared =  mod_hello.la

编译及引用流程
到hello目录里编译安装：apxs -c -i mod_hello.c
编译后会自动生成mod_hello.so文件，当前目录下会生成一个.libs目录，请查阅
同时会复制到Apache module目录下，自动更改权限为644

在/etc/apache2/mods-enabled目录下新建文件：（被“apache2.conf”自动引用）
hello.conf文件：

<IfModule mod_hello.c>
    <Location /hello>
        SetHandler hello
    </Location>

    <IfModule mod_hello.c>
    </IfModule>

</IfModule>

# vim: syntax=apache ts=4 sw=4 sts=4 sr noet

hello.load文件：

LoadModule hello_module /usr/lib/apache2/modules/mod_hello.so

重启Apache服务器即可。

实验现象
在浏览器中输入：http://网址/hello

说明
我的Apache服务器似乎没有httpd。
最后一张图内容不必较真