apache httpd module 笔记

下面以log_config作例子

1 在modules.c 声明了这个变量.

#include "httpd.h"
#include "http_config.h"
extern module core_module;
......
extern module log_config_module;
......
extern module netware_module;

module *ap_prelinked_modules[] = {
  &core_module, /* core must come first */
......
  &log_config_module,
......
  &netware_module,
  NULL
};

ap_module_symbol_t ap_prelinked_module_symbols[] = {
  {"core_module", &core_module},
  ......
  {"log_config_module", &log_config_module},
......
  {"netware_module", &netware_module},
  {NULL, NULL}
};

module *ap_preloaded_modules[] = {
  &core_module,
  ......
  &log_config_module,
  ......
  &netware_module,
  NULL
};

2 在 mod_log_config.c 定义了这个变量:

module AP_MODULE_DECLARE_DATA log_config_module;

变量定义/初始化:

AP_DECLARE_MODULE(log_config) =
{
    STANDARD20_MODULE_STUFF,    /* 这个展开其实就是一些值 */
    NULL,                       /* create per-dir config */
    NULL,                       /* merge per-dir config */
    make_config_log_state,      /* server config */
    merge_config_log_state,     /* merge server config */
    config_log_cmds,            /* command apr_table_t */
    register_hooks              /* register hooks */
};

其实就是定义了一个 struct module_struct的结构体变量 log_config_module, 然后对其进行初始化.

typedef struct module_struct module;
struct module_struct {
    /** API version, *not* module version; check that module is
     * compatible with this version of the server.
     */
    int version;
    /** API minor version. Provides API feature milestones. Not checked
     *  during module init */
    int minor_version;
    /** Index to this modules structures in config vectors.  */
    int module_index;

    /** The name of the module's C file */
    const char *name;
    /** The handle for the DSO.  Internal use only */
    void *dynamic_load_handle;

    /** A pointer to the next module in the list
     *  @var module_struct *next
     */
    struct module_struct *next;

    /** Magic Cookie to identify a module structure;  It's mainly
     *  important for the DSO facility (see also mod_so).  */
    unsigned long magic;

    /** Function to allow MPMs to re-write command line arguments.  This
     *  hook is only available to MPMs.
     *  @param The process that the server is running in.
     */
    void (*rewrite_args) (process_rec *process);
    /** Function to allow all modules to create per directory configuration
     *  structures.
     *  @param p The pool to use for all allocations.
     *  @param dir The directory currently being processed.
     *  @return The per-directory structure created
     */
    void *(*create_dir_config) (apr_pool_t *p, char *dir);
    /** Function to allow all modules to merge the per directory configuration
     *  structures for two directories.
     *  @param p The pool to use for all allocations.
     *  @param base_conf The directory structure created for the parent directory.
     *  @param new_conf The directory structure currently being processed.
     *  @return The new per-directory structure created
     */
    void *(*merge_dir_config) (apr_pool_t *p, void *base_conf, void *new_conf);
    /** Function to allow all modules to create per server configuration
     *  structures.
     *  @param p The pool to use for all allocations.
     *  @param s The server currently being processed.
     *  @return The per-server structure created
     */
    void *(*create_server_config) (apr_pool_t *p, server_rec *s);
    /** Function to allow all modules to merge the per server configuration
     *  structures for two servers.
     *  @param p The pool to use for all allocations.
     *  @param base_conf The directory structure created for the parent directory.
     *  @param new_conf The directory structure currently being processed.
     *  @return The new per-directory structure created
     */
    void *(*merge_server_config) (apr_pool_t *p, void *base_conf,
                                  void *new_conf);

    /** A command_rec table that describes all of the directives this module
     * defines. */
    const command_rec *cmds;

    /** A hook to allow modules to hook other points in the request processing.
     *  In this function, modules should call the ap_hook_*() functions to
     *  register an interest in a specific step in processing the current
     *  request.
     *  @param p the pool to use for all allocations
     */
    void (*register_hooks) (apr_pool_t *p);
};

3 模块使用

3.1 模块初始化基本流程

int main(int argc, const char * const argv[])
=> process = init_process(&argc, &argv);
=> error = ap_setup_prelinked_modules(process);
    => loop ap_prelinked_modules 
        =>ap_add_module(*m, process->pconf, NULL); 
            => ap_add_module_commands(m, p);  //  设置 m->cmds 保存的命令函数
            => ap_register_hooks(m, p);  // 调用该模块的注册函数 m->register_hooks(p); 注册钩子
        => apr_hook_sort_all(); //上面注册完钩子，这里执行排序所有钩子
=> ap_run_rewrite_args(process); 
    =>  loop all module    // 循环调用所以module的 rewrite_args 函数
       => (*m->rewrite_args)(process); 
=> 判断参数，并调用相应处理函数
=> ap_server_conf = ap_read_config(process, ptemp, confname, &ap_conftree);  // 读取配置
    => server_rec *s = init_server_config(process, p); // 创建服务配置变量 s，并初始化默认值。  server_rec: 保存配置的链表节点
        => init_config_globals(p);
    => process_command_config(s, ap_server_pre_read_config, conftree, p, ptemp);
    => confname = ap_server_root_relative(p, filename);
    => error = ap_process_resource_config(s, confname, conftree, p, ptemp);
=> error = ap_check_mpm();
=> error = process_command_config(s, ap_server_post_read_config, conftree, p, ptemp);
=> 

钩子排序和具体说明，参考  http://blog.youkuaiyun.com/conezxy/article/details/1897989   http://blog.youkuaiyun.com/conezxy/article/details/1898000