十五、Nginx 示例: hello handler 模块

示例: hello handler 模块

在前面已经看到了这个 hello handler module 的部分重要的结构。该模块提供了 2 个配置指令,仅可以出现在 location 指令的作用域中。这两个指令是 hello_string, 该指令接受一个参数来设置显示的字符串。如果没有跟参数,那么就使用默认的字符串作为响应字符串。

另一个指令是 hello_counter,如果设置为 on,则会在响应的字符串后面追加 Visited Times:的字样,以统计请求的次数。

这里有两点注意一下:

1、 对于flag类型的配置指令,当值为off的时候,使用ngx_conf_set_flag_slot函数,会转化为0,为on,则转化为非0;
2、 另外一个是,我提供了merge_loc_conf函数,但是却没有设置到模块的上下文定义中这样有一个缺点,就是如果一个指令没有出现在配置文件中的时候,配置信息中的值,将永远会保持在create_loc_conf中的初始化的值那如果,在类似create_loc_conf这样的函数中,对创建出来的配置信息的值,没有设置为合理的值的话,后面用户又没有配置,就会出现问题;

下面来完整的给出 ngx_http_hello_module 模块的完整代码。

#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;

通过上面一些介绍,我相信大家都能对整个示例模块有一个比较好的理解。唯一可能感觉有些理解困难的地方在于ngx_http_hello_handler 函数里面产生和设置输出。但其实大家在本书的前面的相关章节都可以看到对 ngx_buf_t 和 request 等相关数据结构的说明。如果仔细看了这些地方的说明的话,应该对这里代码的实现就比较容易理解了。因此,这里不再赘述解释。