Openresty学习（一）：通过子请求和drizzle模块访问mysql数据库来响应客户端请求

Subrequest是由HTTP框架提供的一种分解复杂请求的设计模式，它可以把原始请求分解为许多子请求，由多个子请求协同完成一个用户请求。原理：子请求使用upstream机制访问上游服务器，由父请求根据上游响应重新构响应造返回下游客户端。主要流程如下：

1. 在nginx.conf配置文件中配置子请求处理方式

2.构造子请求并启动

3. 子请求执行结束处理

4. 父请求被激活时处理

在学习过程中发现，网上关于sub request的介绍都是基于“访问上证股市行情”的例子，不得不说，该程序对于入门学习非常好。可是对于进一步学习并应用该技术，则没有过多的例子可以参考。本文通过“运用子请求和drizzles模块访问mysql”例子再次诠释sub request的使用。

本例程涉及应用：

1. 后端访问配置方式（drizzle 访问mysql配置）

2.子请求基于upstream机制的处理配置

3. Cjson解析消息体（编译上述模块时，请安装Cjson）

本例子程序的处理逻辑：

1. 命令行通过curl（POST方式）发送请求数据（JSON格式）到服务器

2.nginx收到消息体后，解析并打印，构造子请求（ URL：/mysql_query）访问Mysql数据库后端

3.nginx处理子请求：通过upstream机制访问数据库，URL（/mysql）

4.nginx通过drizzle模块访问数据库，读取数据，并通过upstream模块返回数据

5.子请求回调函数解析、保存查询到数据

6.主请求回调函数构造应答数据，返回给客户端

处理流程：nginx 主请求 -->nginx 子请求-->/mysql_query-->/mysql-->drizzle->mysql数据库

配置：

       upstream backend {drizzle_server localhost:3306 dbname=test password=xxxx user=root protocol=mysql;}location /mysql_test{client_body_in_single_buffer on;sub_request_mysql test;//test为参数，此例程未使用}location /mysql {set $my_sql 'select * from student limit 3';drizzle_query $my_sql;drizzle_pass backend;drizzle_connect_timeout    500ms; # default 60sdrizzle_send_query_timeout 2s;    # default 60sdrizzle_recv_cols_timeout  1s;    # default 60sdrizzle_recv_rows_timeout  1s;    # default 60srds_json on;}//子请求查询数据库，此处使用upstream机制location /mysql_query {proxy_pass http://localhost/mysql;#return 200;#return 200 '{"status":"success","result":"nginx json"}';}

root@iZ2ze3uk97m2bfv681kyx4Z:~# curl -i -X POST -H "'Content-type':'application/json'" -d '{"name":"test"}'  http://localhost:80/nestle
HTTP/1.1 200 OK
Server: openresty/1.13.6.1
Date: Tue, 01 May 2018 06:10:24 GMT
Content-Type: text/plain; charset=GBK
Content-Length: 104
Connection: keep-alive[{"id":1,"name":"zhang1","age":0},{"id":3,"name":"zhang-02","age":0},{"id":5,"name":"zhang-03","age":0}]

源码：

ngx_http_sub_request_mysql_module.c:#include 
#include 
#include #include "cJSON.h"typedef struct {ngx_str_t output_words;ngx_uint_t flag;
} ngx_http_sub_request_mysql_loc_conf_t;static char* ngx_http_sub_request_mysql(ngx_conf_t* cf, ngx_command_t* cmd, void* conf);static void* ngx_http_sub_request_mysql_create_loc_conf(ngx_conf_t* cf);static char* ngx_http_sub_request_mysql_merge_loc_conf(ngx_conf_t* cf, void* parent, void* child);static ngx_command_t ngx_http_sub_request_mysql_commands[] = {{ngx_string("sub_request_mysql"), // The command nameNGX_HTTP_LOC_CONF | NGX_CONF_TAKE1,ngx_http_sub_request_mysql, // The command handlerNGX_HTTP_LOC_CONF_OFFSET,offsetof(ngx_http_sub_request_mysql_loc_conf_t, output_words),NULL},ngx_null_command
};// Structure for the HelloWorld context
static ngx_http_module_t ngx_http_sub_request_mysql_module_ctx = {NULL,NULL,NULL,NULL,NULL,NULL,ngx_http_sub_request_mysql_create_loc_conf,ngx_http_sub_request_mysql_merge_loc_conf
};// Structure for the HelloWorld module, the most important thing
ngx_module_t ngx_http_sub_request_mysql_module = {NGX_MODULE_V1,&ngx_http_sub_request_mysql_module_ctx,ngx_http_sub_request_mysql_commands,NGX_HTTP_MODULE,NULL,NULL,NULL,NULL,NULL,NULL,NULL,NGX_MODULE_V1_PADDING
};typedef struct {ngx_str_t name;ngx_str_t db_request_data;
} ngx_http_extern_request_mysql_ctx_t;static void extern_db_request_post_handler(ngx_http_request_t *r)
{ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"%s: status[%d]",__FUNCTION__, r->headers_out.status); if (r->headers_out.status != NGX_HTTP_OK){ngx_http_finalize_request(r, r->headers_out.status);return;}ngx_http_extern_request_mysql_ctx_t *my_ctx = ngx_http_get_module_ctx(r,ngx_http_sub_request_mysql_module);int bodylen = my_ctx->db_request_data.len;r->headers_out.content_length_n = bodylen;ngx_buf_t *b = ngx_create_temp_buf(r->pool,bodylen);ngx_snprintf(b->pos, bodylen, (char *)my_ctx->db_request_data.data);b->last = b->pos + bodylen;b->last_buf = 1;ngx_chain_t out;out.buf = b;out.next = NULL;static ngx_str_t type = ngx_string("text/plain; charset=GBK");r->headers_out.content_type= type;r->headers_out.status =NGX_HTTP_OK; r->connection->buffered |= NGX_HTTP_WRITE_BUFFERED;ngx_int_t ret = ngx_http_send_header(r);ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"%s: send header ret[%d]", __FUNCTION__, ret);ret = ngx_http_output_filter(r,&out);ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"%s: send body ret[%d]", __FUNCTION__, ret); ngx_http_finalize_request(r,ret);
}static ngx_int_t extern_db_sub_req_post_handler(ngx_http_request_t *r,void *data, ngx_int_t rc)
{ngx_str_t response_data;ngx_http_request_t *pr = r->parent;ngx_http_extern_request_mysql_ctx_t *my_ctx = ngx_http_get_module_ctx(pr,ngx_http_sub_request_mysql_module);pr->headers_out.status = r->headers_out.status;ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"%s: %d",__FUNCTION__, r->headers_out.status); if (r->headers_out.status == NGX_HTTP_OK){int flag = 0;ngx_buf_t *sub_recv_buf = &r->upstream->buffer;response_data.data = sub_recv_buf->pos;response_data.len = ngx_buf_size(sub_recv_buf);ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"data: %d, %V", response_data.len,&response_data);my_ctx->db_request_data.len = response_data.len;my_ctx->db_request_data.data = response_data.data;}pr->write_event_handler = extern_db_request_post_handler;return NGX_OK;
}static void ngx_http_sub_request_mysql_client_body_handler_pt(ngx_http_request_t *r)
{ngx_int_t rc = NGX_OK;char log_buf[32] = {0};u_char body_buf[256] = {0};ngx_buf_t *p_body_buf = NULL;cJSON *root = NULL;cJSON *name = NULL;ngx_http_sub_request_mysql_loc_conf_t* hlcf = NULL;hlcf = ngx_http_get_module_loc_conf(r, ngx_http_sub_request_mysql_module);if (NULL == hlcf){}ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"%s", log_buf);p_body_buf = r->request_body->bufs->buf;ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"length:%d", ngx_buf_size(p_body_buf));ngx_snprintf(body_buf, sizeof(body_buf), "%*s",ngx_buf_size(p_body_buf), p_body_buf->pos);ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"main: receive body:%s", body_buf);root = cJSON_Parse((char *)body_buf);if (NULL == root){return;}name = cJSON_GetObjectItemCaseSensitive(root, "name");if (NULL == name){return;}ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"name: %s", name->valuestring);ngx_http_extern_request_mysql_ctx_t *my_ctx = ngx_http_get_module_ctx(r,ngx_http_sub_request_mysql_module);if (NULL == my_ctx){my_ctx = ngx_palloc(r->pool, sizeof(ngx_http_extern_request_mysql_ctx_t));if (NULL == my_ctx){return;}ngx_http_set_ctx(r, my_ctx, ngx_http_sub_request_mysql_module);}ngx_http_post_subrequest_t *my_sub_req = ngx_palloc(r->pool,sizeof(ngx_http_post_subrequest_t));if (NULL == my_sub_req){return;}my_sub_req->handler = extern_db_sub_req_post_handler;my_sub_req->data = my_ctx;ngx_str_t sub_prefix = ngx_string("/mysql_query?name=hello");ngx_str_t sub_location;sub_location.len =sub_prefix.len;sub_location.data = ngx_palloc(r->pool,sub_location.len);ngx_snprintf(sub_location.data, sub_location.len, "%V",&sub_prefix);ngx_http_request_t *sr = NULL;rc = ngx_http_subrequest(r, &sub_location, NULL,&sr, my_sub_req, NGX_HTTP_SUBREQUEST_IN_MEMORY);if (rc != NGX_OK){return;}return;
}static int ngx_response_info(ngx_http_request_t* r)
{ngx_int_t rc = NGX_OK;ngx_buf_t* b = NULL;ngx_chain_t out[2];cJSON *root = NULL;char json_buf[256] = {0};root = cJSON_CreateObject();cJSON_AddItemToObject(root, "res-info",cJSON_CreateString("no account info in body"));r->headers_out.content_type.len = sizeof("application/json; charset=utf-8") - 1;r->headers_out.content_type.data = (u_char*)"application/json; charset=utf-8";b = ngx_pcalloc(r->pool, sizeof(ngx_buf_t));out[0].buf = b;out[0].next = NULL;snprintf(json_buf, sizeof(json_buf), "%s", cJSON_Print(root));ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"%s,length:%d", json_buf, strlen(json_buf));b->pos = (u_char*)cJSON_Print(root);b->last = b->pos + strlen(json_buf);b->memory = 1;b->last_buf = 1;r->headers_out.status = NGX_HTTP_OK;r->headers_out.content_length_n = strlen(json_buf);rc = ngx_http_send_header(r);if (rc == NGX_ERROR || rc > NGX_OK || r->header_only) {return rc;}rc = ngx_http_output_filter(r, &out[0]);ngx_http_finalize_request(r,rc);cJSON_Delete(root);return rc;
}static ngx_int_t ngx_http_sub_request_mysql_handler(ngx_http_request_t* r) {ngx_int_t rc = NGX_OK;int no_content_flag = 0;if (r->headers_in.content_length){ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"%s: content length is %d", __FUNCTION__,ngx_atoi(r->headers_in.content_length->value.data, r->headers_in.content_length->value.len));}else{no_content_flag = 1;ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"no content");}if (0 == no_content_flag && ngx_atoi(r->headers_in.content_length->value.data, r->headers_in.content_length->value.len) <= 0){ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"in: content length is %d",ngx_atoi(r->headers_in.content_length->value.data, r->headers_in.content_length->value.len));no_content_flag = 1;ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"no content");}ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"no content flag:%d", no_content_flag);if (no_content_flag){return ngx_response_info(r);}rc = ngx_http_read_client_request_body(r,ngx_http_sub_request_mysql_client_body_handler_pt);if (rc >= NGX_HTTP_SPECIAL_RESPONSE){ngx_log_error(NGX_LOG_EMERG, r->connection->log, 0,"%s", "unknown respone");return rc;}return NGX_DONE;
}static void* ngx_http_sub_request_mysql_create_loc_conf(ngx_conf_t* cf) {ngx_http_sub_request_mysql_loc_conf_t* conf;conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_sub_request_mysql_loc_conf_t));if (conf == NULL) {return NGX_CONF_ERROR;}conf->output_words.len = 0;conf->output_words.data = NULL;conf->flag = NGX_CONF_UNSET;return conf;
}static char* ngx_http_sub_request_mysql_merge_loc_conf(ngx_conf_t* cf, void* parent, void* child) {ngx_http_sub_request_mysql_loc_conf_t* prev = parent;ngx_http_sub_request_mysql_loc_conf_t* conf = child;ngx_conf_merge_str_value(conf->output_words, prev->output_words, "Nginx");ngx_conf_merge_uint_value(conf->flag, prev->flag,1);return NGX_CONF_OK;
}static char* ngx_http_sub_request_mysql(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_sub_request_mysql_handler;ngx_conf_set_str_slot(cf, cmd, conf);return NGX_CONF_OK;
}

config:ngx_addon_name=ngx_http_sub_request_mysql_module
HTTP_MODULES="$HTTP_MODULES ngx_http_sub_request_mysql_module"
NGX_ADDON_SRCS="$NGX_ADDON_SRCS $ngx_addon_dir/ngx_http_sub_request_mysql_module.c"

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