nginx-学习笔记6

handler模块的挂载

handler模块必须提供一个真正的处理函数，这个函数负责对来自客户端请求的真正处理。这个函数的处理，既可以选择自己直接生成内容，也可以选择拒绝处理，由后续的handler去进行处理，或者是选择丢给后续的filter进行处理。来看一下这个函数的原型申明。

typedef ngx_int_t (*ngx_http_handler_pt)(ngx_http_request_t *r);

r是http请求。该函数处理成功返回NGX_OK，处理发生错误返回NGX_ERROR，拒绝处理（留给后续的handler进行处理）返回NGX_DECLINE。 返回NGX_OK也就代表给客户端的响应已经生成好了，否则返回NGX_ERROR就发生错误了。

一种方式就是按处理阶段挂载;另外一种挂载方式就是按需挂载。

按处理阶段挂载

为了更精细地控制对于客户端请求的处理过程，nginx把这个处理过程划分成了11个阶段。他们从前到后，依次列举如下：

NGX_HTTP_POST_READ_PHASE:
	读取请求内容阶段
NGX_HTTP_SERVER_REWRITE_PHASE:
	Server请求地址重写阶段
NGX_HTTP_FIND_CONFIG_PHASE:
	配置查找阶段:
NGX_HTTP_REWRITE_PHASE:
	Location请求地址重写阶段
NGX_HTTP_POST_REWRITE_PHASE:
	请求地址重写提交阶段
NGX_HTTP_PREACCESS_PHASE:
	访问权限检查准备阶段
NGX_HTTP_ACCESS_PHASE:
	访问权限检查阶段
NGX_HTTP_POST_ACCESS_PHASE:
	访问权限检查提交阶段
NGX_HTTP_TRY_FILES_PHASE:
	配置项try_files处理阶段
NGX_HTTP_CONTENT_PHASE:
	内容产生阶段
NGX_HTTP_LOG_PHASE:
	日志模块处理阶段

一般情况下，我们自定义的模块，大多数是挂载在NGX_HTTP_CONTENT_PHASE阶段的。挂载的动作一般是在模块上下文调用的postconfiguration函数中。

注意：有几个阶段是特例，它不调用挂载地任何的handler，也就是你就不用挂载到这几个阶段了：

• NGX_HTTP_FIND_CONFIG_PHASE
• NGX_HTTP_POST_ACCESS_PHASE
• NGX_HTTP_POST_REWRITE_PHASE
• NGX_HTTP_TRY_FILES_PHASE

例如一个挂载如下：

static ngx_int_t
ngx_http_hello_init(ngx_conf_t *cf)
{
        ngx_http_handler_pt        *h;
        ngx_http_core_main_conf_t  *cmcf;

        cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);

        h = ngx_array_push(&cmcf->phases[NGX_HTTP_CONTENT_PHASE].handlers);
        if (h == NULL) {
                return NGX_ERROR;
        }

        *h = ngx_http_hello_handler;

        return NGX_OK;
}

使用这种方式挂载的handler也被称为 content phase handlers。

按需挂载

以这种方式挂载的handler也被称为 content handler。

当一个请求进来以后，nginx从NGX_HTTP_POST_READ_PHASE阶段开始依次执行每个阶段中所有handler。执行到 NGX_HTTP_CONTENT_PHASE阶段的时候，如果这个location有一个对应的content handler模块，那么就去执行这个content handler模块真正的处理函数。否则继续依次执行NGX_HTTP_CONTENT_PHASE阶段中所有content phase handlers，直到某个函数处理返回NGX_OK或者NGX_ERROR。

换句话说，当某个location处理到NGX_HTTP_CONTENT_PHASE阶段时，如果有content handler模块，那么NGX_HTTP_CONTENT_PHASE挂载的所有content phase handlers都不会被执行了。

举个例子来说：

static char *
ngx_http_circle_gif(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{
        ngx_http_core_loc_conf_t  *clcf;

        clcf = ngx_http_conf_get_module_loc_conf(cf, ngx_http_core_module);
        clcf->handler = ngx_http_circle_gif_handler;

        return NGX_CONF_OK;
}

下面是本书作者的模块代码：

#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


typedef struct
{
        ngx_str_t hello_string;
        ngx_int_t hello_counter;
}ngx_http_hello_loc_conf_t;

static ngx_int_t ngx_http_hello_init(ngx_conf_t *cf);

static void *ngx_http_hello_create_loc_conf(ngx_conf_t *cf);

static char *ngx_http_hello_string(ngx_conf_t *cf, ngx_command_t *cmd,
        void *conf);
static char *ngx_http_hello_counter(ngx_conf_t *cf, ngx_command_t *cmd,
        void *conf);

static ngx_command_t ngx_http_hello_commands[] = {
   {
                ngx_string("hello_string"),
                NGX_HTTP_LOC_CONF|NGX_CONF_NOARGS|NGX_CONF_TAKE1,
                ngx_http_hello_string,
                NGX_HTTP_LOC_CONF_OFFSET,
                offsetof(ngx_http_hello_loc_conf_t, hello_string),
                NULL },

        {
                ngx_string("hello_counter"),
                NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
                ngx_http_hello_counter,
                NGX_HTTP_LOC_CONF_OFFSET,
                offsetof(ngx_http_hello_loc_conf_t, hello_counter),
                NULL },

        ngx_null_command
};


/*
static u_char ngx_hello_default_string[] = "Default String: Hello, world!";
*/
static int ngx_hello_visited_times = 0;

static ngx_http_module_t ngx_http_hello_module_ctx = {
        NULL,                          /* preconfiguration */
        ngx_http_hello_init,           /* postconfiguration */

        NULL,                          /* create main configuration */
        NULL,                          /* init main configuration */

        NULL,                          /* create server configuration */
        NULL,                          /* merge server configuration */

        ngx_http_hello_create_loc_conf, /* create location configuration */
        NULL                            /* merge location configuration */
};


ngx_module_t ngx_http_hello_module = {
        NGX_MODULE_V1,
        &ngx_http_hello_module_ctx,    /* module context */
        ngx_http_hello_commands,       /* module directives */
        NGX_HTTP_MODULE,               /* module type */
        NULL,                          /* init master */
        NULL,                          /* init module */
        NULL,                          /* init process */
        NULL,                          /* init thread */
        NULL,                          /* exit thread */
        NULL,                          /* exit process */
        NULL,                          /* exit master */
        NGX_MODULE_V1_PADDING
};


static ngx_int_t
ngx_http_hello_handler(ngx_http_request_t *r)
{
        ngx_int_t    rc;
        ngx_buf_t   *b;
        ngx_chain_t  out;
        ngx_http_hello_loc_conf_t* my_conf;
        u_char ngx_hello_string[1024] = {0};
        ngx_uint_t content_length = 0;

        ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "ngx_http_hello_handler is called!");

        my_conf = ngx_http_get_module_loc_conf(r, ngx_http_hello_module);
        if (my_conf->hello_string.len == 0 )
        {
                ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "hello_string is empty!");
                return NGX_DECLINED;
        }


        if (my_conf->hello_counter == NGX_CONF_UNSET
                || my_conf->hello_counter == 0)
        {
                ngx_sprintf(ngx_hello_string, "%s", my_conf->hello_string.data);
        }
        else
        {
                ngx_sprintf(ngx_hello_string, "%s Visited Times:%d", my_conf->hello_string.data,
                        ++ngx_hello_visited_times);
        }
        ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "hello_string:%s", ngx_hello_string);
        content_length = ngx_strlen(ngx_hello_string);

        /* we response to 'GET' and 'HEAD' requests only */
        if (!(r->method & (NGX_HTTP_GET|NGX_HTTP_HEAD))) {
                return NGX_HTTP_NOT_ALLOWED;
        }

        /* discard request body, since we don't need it here */
        rc = ngx_http_discard_request_body(r);

        if (rc != NGX_OK) {
                return rc;
        }

        /* set the 'Content-type' header */
        /*
         *r->headers_out.content_type.len = sizeof("text/html") - 1;
         *r->headers_out.content_type.data = (u_char *)"text/html";
         */
        ngx_str_set(&r->headers_out.content_type, "text/html");


        /* send the header only, if the request type is http 'HEAD' */
        if (r->method == NGX_HTTP_HEAD) {
                r->headers_out.status = NGX_HTTP_OK;
                r->headers_out.content_length_n = content_length;

                return ngx_http_send_header(r);
        }

        /* allocate a buffer for your response body */
        b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));
        if (b == NULL) {
                return NGX_HTTP_INTERNAL_SERVER_ERROR;
        }

        /* attach this buffer to the buffer chain */
        out.buf = b;
        out.next = NULL;

        /* adjust the pointers of the buffer */
        b->pos = ngx_hello_string;
        b->last = ngx_hello_string + content_length;
        b->memory = 1;    /* this buffer is in memory */
        b->last_buf = 1;  /* this is the last buffer in the buffer chain */

        /* set the status line */
        r->headers_out.status = NGX_HTTP_OK;
        r->headers_out.content_length_n = content_length;

        /* send the headers of your response */
        rc = ngx_http_send_header(r);

        if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {
                return rc;
        }

        /* send the buffer chain of your response */
        return ngx_http_output_filter(r, &out);
}

static void *ngx_http_hello_create_loc_conf(ngx_conf_t *cf)
{
        ngx_http_hello_loc_conf_t* local_conf = NULL;
        local_conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_hello_loc_conf_t));
        if (local_conf == NULL)
        {
                return NULL;
        }

        ngx_str_null(&local_conf->hello_string);
        local_conf->hello_counter = NGX_CONF_UNSET;

        return local_conf;
}

/*
static char *ngx_http_hello_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child)
{
        ngx_http_hello_loc_conf_t* prev = parent;
        ngx_http_hello_loc_conf_t* conf = child;

        ngx_conf_merge_str_value(conf->hello_string, prev->hello_string, ngx_hello_default_string);
        ngx_conf_merge_value(conf->hello_counter, prev->hello_counter, 0);

        return NGX_CONF_OK;
}*/

static char *
ngx_http_hello_string(ngx_conf_t *cf, ngx_command_t *cmd, void *conf)
{

        ngx_http_hello_loc_conf_t* local_conf;


        local_conf = conf;
        char* rv = ngx_conf_set_str_slot(cf, cmd, conf);

        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "hello_string:%s", local_conf->hello_string.data);

        return rv;
}


static char *ngx_http_hello_counter(ngx_conf_t *cf, ngx_command_t *cmd,
        void *conf)
{
        ngx_http_hello_loc_conf_t* local_conf;

        local_conf = conf;

        char* rv = NULL;

        rv = ngx_conf_set_flag_slot(cf, cmd, conf);


        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "hello_counter:%d", local_conf->hello_counter);
        return rv;
}

static ngx_int_t
ngx_http_hello_init(ngx_conf_t *cf)
{
        ngx_http_handler_pt        *h;
        ngx_http_core_main_conf_t  *cmcf;

        cmcf = ngx_http_conf_get_module_main_conf(cf, ngx_http_core_module);

        h = ngx_array_push(&cmcf->phases[NGX_HTTP_CONTENT_PHASE].handlers);
        if (h == NULL) {
                return NGX_ERROR;
        }

        *h = ngx_http_hello_handler;

        return NGX_OK;
}