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nginx 学习五 filter模块简介和实现一个简单的filter模块
1 nginx过滤模块简介
过滤(filter)模块是过滤响应头和内容的模块,可以对回复的头和内容进行处理。它的处理时间在获取回复内容之后,
向用户发送响应之前。它的处理过程分为两个阶段,过滤HTTP回复的头部和主体,在这两个阶段可以分别对头部和主体
进行修改。
2 过滤模块执行顺序
2.1 ngx_http_output_(head, body)_filter_pt
先看一下nginx常用的过滤模块,在ngx_moudles.c中有一下代码:
ngx_module_t *ngx_modules[] = { ...... &ngx_http_write_filter_module, &ngx_http_header_filter_module, &ngx_http_chunked_filter_module, &ngx_http_range_header_filter_module, &ngx_http_gzip_filter_module, &ngx_http_postpone_filter_module, &ngx_http_ssi_filter_module, &ngx_http_charset_filter_module, &ngx_http_userid_filter_module, &ngx_http_myfilter_module, &ngx_http_headers_filter_module, &ngx_http_copy_filter_module, &ngx_http_range_body_filter_module, &ngx_http_not_modified_filter_module, NULL };
nginx过滤模块的执行顺序是从ngx_http_not_modified_filter_module 到 ngx_http_write_filter_module。下面我们来看一下这个执行
顺序是怎么用链表构成的。
既然是用链表构成的,肯定是要有链表指针,而且有两个,一个链接处理头部的函数,一个链接处理包体的函数,下面来看看这两
个链表指针的定义:
typedef ngx_int_t (ngx_http_output_header_filter_pt)(ngx_http_request_t *r); typedef ngx_int_t (ngx_http_output_body_filter_pt)(ngx_http_request_t *r, ngx_chain_t *in);
ngx_http_output_header_filter_pt 指向处理头部的函数指针,每一个过滤模块中如果要处理头部,就必要定义一个局部的这种类型的指针和函数。
ngx_http_output_body_filter_pt 指向处理包体的函数指针,每一个过滤模块中如果要处理包体,就必要定义一个局部的这种类型的指针和函数。
2.2 过滤模块链表的入口
过滤模块链表的入口是两个静态的函数指针:
extern ngx_http_output_header_filter_pt ngx_http_top_header_filter; extern ngx_http_output_body_filter_pt ngx_http_body_body_filter;
当执行ngx_http_send_header发送http头部时,就开始从ngx_http_tou_header_filter指针遍历所有的http头部过滤模块。
ngx_http_send_header:
ngx_int_t ngx_http_send_header(ngx_http_request_t *r) { if (r->err_status) { r->headers_out.status = r->err_status; r->headers_out.status_line.len = 0; } return ngx_http_top_header_filter(r);//链表头,指向第一个过滤头部的模块函数 }
当执行ngx_http_output_filter发送包体时,就从ngx_http_top_body_filter指针遍历所有的http包体过滤模块。
ngx_http_output_filter:
ngx_int_t ngx_http_output_filter(ngx_http_request_t *r, ngx_chain_t *in) { ngx_int_t rc; ngx_connection_t *c; c = r->connection; rc = ngx_http_top_body_filter(r, in); if (rc == NGX_ERROR) { c->error = 1; } return rc;//链表头,指向第一个过滤包体的模块函数 }
那么nginx是怎样用ngx_http_top_header_filter 和 ngx_http_top_body_filter把所有过滤头部的模块和所有过滤包体的模块链接起来的呢?
2.3 过滤模块的链接
原来每个过滤模块都定义了两个(这里假设每个过滤模块都处理头部和包体)static的函数指针:
static ngx_http_output_header_filter_pt ngx_http_next_header_filter; static ngx_http_output_body_filter_pt ngx_http_next_body_filter;
ngx_http_next_header_filter来保存ngx_http_top_header_filter指向的处理模块函数,而ngx_http_top_header_filter则指向本模块处理头部的过滤函数。
ngx_http_next_body_filter来保存ngx_http_top_body_filter指向的处理模块函数,而ngx_http_top_body_filter则指向本模块处理包体的过滤函数。
代码表示如下:
ngx_http_next_header_filter = ngx_http_top_header_filter; ngx_http_top_header_filter = ngx_http_current_myfilter_header_filter;//处理头部的过滤函数 ngx_http_next_body_filter = ngx_http_top_body_filter; ngx_http_top_body_filter = ngx_http_current_myfilter_body_filter;//处理包体的过滤函数
这样所有过滤模块就被链接起来了。
比如现在有两个过滤模块filter_a, filter_b,filter_a模块先定义,filter_b模块后定义。
在filter_a 里面有如下代码:
ngx_http_next_header_filter_a = ngx_http_top_header_filter; ngx_http_top_header_filter = ngx_http_filtera_header_filter; ngx_http_next_body_filter_a = ngx_http_top_body_filter; ngx_http_top_body_filter = ngx_http_filtera_body_filter;
注意这时ngx_http_header_filter指向filter_a的头部处理函数,ngx_http_top_body_filter指向filter_a的包体处理函数。
在filter_b里面有如下代码:
ngx_http_next_header_filter_b = ngx_http_top_header_filter; ngx_http_top_header_filter = ngx_http_filterb_header_filter; ngx_http_next_body_filter_b = ngx_http_top_body_filter; ngx_http_top_body_filter = ngx_http_filterb_body_filter;
这样以后,ngx_http_next_header_filter_b保存的则是ngx_http_filtera_header_filter,即指向filtera中处理头部的过滤函数,filtera和filterb的头部过滤链表就建立起来了。
同样,ngx_http_next_body_filter_b保存的是ngx_http_filterb_body_filter,即指向filtera中处理包体的过滤函数,filtera和filterb的包体过滤链表就建立起来了。
而此时ngx_http_top_header_filter保存的是filterb的头部过滤函数,ngx_http_top_body_filter保存的是filterb的包体过滤函数。
我们实现filterb的头部过滤函数时的代码往往如下:
ngx_int_t ngx_http_next_header_filter_b(ngx_http_request_r *r) { //处理头部的代码 ...... return ngx_http_next_header_filter_b(r, in);//调用filtera处理头部的函数 }
实现filterb的包体过滤函数时的代码往往如下:
ngx_int_t ngx_http_next_body_filter_b(ngx_http_request_t *r, ngx_chain_t *in) { //处理包体的代码 ...... return ngx_http_header_filter_b(r, in); //调用filtera处理包体的函数 }
呵呵,这样模块filtera和模块filterb就串联起来了,并且filterb的执行在filtera执行之前,这就解释了2.1中模块的执行为什么是倒序。
假如有模块filterc、filterd......都是按照filtera和filterb链接的方式链接在两个链表中的。
3实现一个简单的过滤模块
实现一个简单的过滤模块在头部加入字符串"[my filter prefix] "。
3.1config的编写:
ngx_addon_name=ngx_http_myfilter_module HTTP_FILTER_MODULES="$HTTP_FILTER_MODULES ngx_http_myfilter_module" NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ngx_addon_dir/ngx_http_myfilter_module.c"
注意与handler模块的区别:HTTP_FILTER_MODULES="$HTTP_FILTER_MODULES ngx_http_myfilter_module"
刚开始我就在这里跳进坑了,找了好久,原来不是handler模块中写的HTTP_MODULES。
3.2代码编写
其实实现挺简单的分为几个步骤:
1)三个模块结构体的实现:ngx_command_t 、ngx_http_moudle_t、ngx_moudle_t可以参考这篇文章
2)把当前处理头部和包体的过滤函数链接如链表
3)分别实现过滤头部的函数和过滤包体的函数
第一步 代码:
typedef struct { ngx_flag_t arg_flag; }ngx_http_myfilter_loc_conf_t; typedef struct { ngx_int_t flag_count; }ngx_http_myfilter_ctx_t; static ngx_str_t filter_prefix = ngx_string("[my filter prefix]"); //static限定这两个变量只在当前文件中有效 static ngx_http_output_header_filter_pt ngx_http_next_header_filter; static ngx_http_output_body_filter_pt ngx_http_next_body_filter; static char* ngx_http_myfilter_set(ngx_conf_t *cf, ngx_command_t *cmd, void *conf); static void* ngx_http_myfilter_create_loc_conf(ngx_conf_t *cf); static char* ngx_http_myfilter_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child); static ngx_int_t ngx_http_myfilter_post_config(ngx_conf_t *cf); static ngx_int_t ngx_http_myfilter_header_filter(ngx_http_request_t *r); static ngx_int_t ngx_http_myfilter_body_filter(ngx_http_request_t *r, ngx_chain_t *in); static ngx_command_t ngx_http_myfilter_commands[] = { { ngx_string("add_prefix"), NGX_HTTP_LOC_CONF|NGX_CONF_FLAG, ngx_http_myfilter_set, NGX_HTTP_LOC_CONF_OFFSET, offsetof(ngx_http_myfilter_loc_conf_t, arg_flag), NULL }, ngx_null_command }; static ngx_http_module_t ngx_http_myfilter_module_ctx = { NULL, ngx_http_myfilter_post_config, NULL, NULL, NULL, NULL, ngx_http_myfilter_create_loc_conf, ngx_http_myfilter_merge_loc_conf }; ngx_module_t ngx_http_myfilter_module = { NGX_MODULE_V1, &ngx_http_myfilter_module_ctx, ngx_http_myfilter_commands, NGX_HTTP_MODULE, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NGX_MODULE_V1_PADDING };
第二步代码:
static ngx_int_t ngx_http_myfilter_post_config(ngx_conf_t *cf) { ngx_http_next_header_filter = ngx_http_top_header_filter; ngx_http_top_header_filter = ngx_http_myfilter_header_filter; ngx_http_next_body_filter = ngx_http_top_body_filter; ngx_http_top_body_filter = ngx_http_myfilter_body_filter; ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "post config is called!"); return NGX_OK; }
第三步代码:
static ngx_int_t ngx_http_myfilter_header_filter(ngx_http_request_t *r) { if (r->headers_out.status != NGX_HTTP_OK) { ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "headers_out.status = %d", r->headers_out.status); return ngx_http_next_header_filter(r); } ngx_http_myfilter_loc_conf_t *mlcf; mlcf = ngx_http_get_module_loc_conf(r, ngx_http_myfilter_module); if (mlcf->arg_flag == 0) //flag = 0,表示不加前缀 { ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "arg_flag = 0"); return ngx_http_next_header_filter(r); } ngx_http_myfilter_ctx_t *mctx; mctx = ngx_http_get_module_ctx(r, ngx_http_myfilter_module); if (mctx != NULL) //mctx不为空,表示这个头部已经处理过,不许要再处理了 { return ngx_http_next_header_filter(r); } mctx = ngx_pcalloc(r->pool, sizeof(ngx_http_myfilter_ctx_t)); if (mctx == NULL) { return NGX_ERROR; } ngx_http_set_ctx(r, mctx, ngx_http_myfilter_module); mctx->flag_count = 0; //0:初始化为不加前缀 ngx_str_t type = ngx_string("text/plain"); if (r->headers_out.content_type.len >= type.len && ngx_strncasecmp(r->headers_out.content_type.data, type.data, type.len) == 0) { mctx->flag_count = 1; //1:头部类型为“text/plain”的要加前缀 if (r->headers_out.content_length_n > 0) { r->headers_out.content_length_n += filter_prefix.len; } } return ngx_http_next_header_filter(r); } static ngx_int_t ngx_http_myfilter_body_filter(ngx_http_request_t *r, ngx_chain_t *in) { ngx_http_myfilter_ctx_t *mctx; mctx = ngx_http_get_module_ctx(r, ngx_http_myfilter_module); if (mctx == NULL || mctx->flag_count != 1) { return ngx_http_next_body_filter(r, in); } mctx->flag_count = 2; ngx_buf_t* buf = ngx_create_temp_buf(r->pool, filter_prefix.len); buf->start = filter_prefix.data; buf->pos = filter_prefix.data; buf->last = filter_prefix.data + filter_prefix.len; ngx_chain_t* out = ngx_alloc_chain_link(r->pool); out->buf = buf; out->next = in; return ngx_http_next_body_filter(r, out); }
http://blog.csdn.net/xiaoliangsky/article/details/39522357
完整代码以后参考:
#include <ngx_config.h> #include <ngx_core.h> #include <ngx_http.h> typedef struct { ngx_flag_t arg_flag; }ngx_http_myfilter_loc_conf_t; typedef struct { ngx_int_t flag_count; }ngx_http_myfilter_ctx_t; static ngx_str_t filter_prefix = ngx_string("[my filter prefix]"); //static限定这两个变量只在当前文件中有效 static ngx_http_output_header_filter_pt ngx_http_next_header_filter; static ngx_http_output_body_filter_pt ngx_http_next_body_filter; static char* ngx_http_myfilter_set(ngx_conf_t *cf, ngx_command_t *cmd, void *conf); static void* ngx_http_myfilter_create_loc_conf(ngx_conf_t *cf); static char* ngx_http_myfilter_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child); static ngx_int_t ngx_http_myfilter_post_config(ngx_conf_t *cf); static ngx_int_t ngx_http_myfilter_header_filter(ngx_http_request_t *r); static ngx_int_t ngx_http_myfilter_body_filter(ngx_http_request_t *r, ngx_chain_t *in); static ngx_command_t ngx_http_myfilter_commands[] = { { ngx_string("add_prefix"), NGX_HTTP_LOC_CONF|NGX_CONF_FLAG, ngx_http_myfilter_set, NGX_HTTP_LOC_CONF_OFFSET, offsetof(ngx_http_myfilter_loc_conf_t, arg_flag), NULL }, ngx_null_command }; static ngx_http_module_t ngx_http_myfilter_module_ctx = { NULL, ngx_http_myfilter_post_config, NULL, NULL, NULL, NULL, ngx_http_myfilter_create_loc_conf, ngx_http_myfilter_merge_loc_conf }; ngx_module_t ngx_http_myfilter_module = { NGX_MODULE_V1, &ngx_http_myfilter_module_ctx, ngx_http_myfilter_commands, NGX_HTTP_MODULE, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NGX_MODULE_V1_PADDING }; static ngx_int_t ngx_http_myfilter_post_config(ngx_conf_t *cf) { ngx_http_next_header_filter = ngx_http_top_header_filter; ngx_http_top_header_filter = ngx_http_myfilter_header_filter; ngx_http_next_body_filter = ngx_http_top_body_filter; ngx_http_top_body_filter = ngx_http_myfilter_body_filter; ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "post config is called!"); return NGX_OK; } static char* ngx_http_myfilter_set(ngx_conf_t *cf, ngx_command_t *cmd, void *conf) { ngx_http_myfilter_loc_conf_t *mlcf = conf; char* rc = ngx_conf_set_flag_slot(cf, cmd, conf); ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "arg_flag = %d", mlcf->arg_flag); return rc; } static void* ngx_http_myfilter_create_loc_conf(ngx_conf_t *cf) { ngx_http_myfilter_loc_conf_t *mlcf; mlcf = ngx_pcalloc(cf->pool, sizeof(ngx_http_myfilter_loc_conf_t)); if (mlcf == NULL) { return NULL; } mlcf->arg_flag = NGX_CONF_UNSET; return mlcf; } static char* ngx_http_myfilter_merge_loc_conf(ngx_conf_t *cf, void *parent, void *child) { ngx_http_myfilter_loc_conf_t* prev = parent; ngx_http_myfilter_loc_conf_t* conf = child; ngx_conf_merge_value(conf->arg_flag, prev->arg_flag, 0); return NGX_CONF_OK; } static ngx_int_t ngx_http_myfilter_header_filter(ngx_http_request_t *r) { if (r->headers_out.status != NGX_HTTP_OK) { ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "headers_out.status = %d", r->headers_out.status); return ngx_http_next_header_filter(r); } ngx_http_myfilter_loc_conf_t *mlcf; mlcf = ngx_http_get_module_loc_conf(r, ngx_http_myfilter_module); if (mlcf->arg_flag == 0) //flag = 0,表示不加前缀 { ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0, "arg_flag = 0"); return ngx_http_next_header_filter(r); } ngx_http_myfilter_ctx_t *mctx; mctx = ngx_http_get_module_ctx(r, ngx_http_myfilter_module); if (mctx != NULL) //mctx不为空,表示这个头部已经处理过,不许要再处理了 { return ngx_http_next_header_filter(r); } mctx = ngx_pcalloc(r->pool, sizeof(ngx_http_myfilter_ctx_t)); if (mctx == NULL) { return NGX_ERROR; } ngx_http_set_ctx(r, mctx, ngx_http_myfilter_module); mctx->flag_count = 0; //0:初始化为不加前缀 ngx_str_t type = ngx_string("text/plain"); if (r->headers_out.content_type.len >= type.len && ngx_strncasecmp(r->headers_out.content_type.data, type.data, type.len) == 0) { mctx->flag_count = 1; //1:头部类型为“text/plain”的要加前缀 if (r->headers_out.content_length_n > 0) { r->headers_out.content_length_n += filter_prefix.len; } } return ngx_http_next_header_filter(r); } static ngx_int_t ngx_http_myfilter_body_filter(ngx_http_request_t *r, ngx_chain_t *in) { ngx_http_myfilter_ctx_t *mctx; mctx = ngx_http_get_module_ctx(r, ngx_http_myfilter_module); if (mctx == NULL || mctx->flag_count != 1) { return ngx_http_next_body_filter(r, in); } mctx->flag_count = 2; ngx_buf_t* buf = ngx_create_temp_buf(r->pool, filter_prefix.len); buf->start = filter_prefix.data; buf->pos = filter_prefix.data; buf->last = filter_prefix.data + filter_prefix.len; ngx_chain_t* out = ngx_alloc_chain_link(r->pool); out->buf = buf; out->next = in; return ngx_http_next_body_filter(r, out); }
注意:因为处理头部的type类型为"text/plain",所以应该访问txt类型的文本才有效。
在nginx/html文件里面创建一个test.txt,内容为:hhhhh。
然后在浏览器中输入:localhost/test.txt
nginx 学习五 filter模块简介和实现一个简单的filter模块