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使用nginx, memcached, libevent, mysql实现url排重

已有 2072 次阅读2013-3-4 22:48 | mysql

0. 思路
用nginx在前端做反向代理, 把请求转到c写的程序url_query, 这个程序去memcached里取url, 没有则关掉connection.
此时nginx会fallback到另一个C写的程序url_set, 该程序去查mysql数据, 如果有则存memcached, 同时返回HTTP 200, 否则返回HTTP 404.

这样写的好处就是url_query挂掉不影响服务, memcached挂掉也不影响服务.
而且可以在不同的服务器上开多个url_query, url_set, memcached.

1. 数据表

CREATE TABLE `url` (
    `url` VARCHAR(1024),
    `date` DATE,
    KEY `url` (`url`)
);

2. config.h

#define MAXLEN 2048 
 
#define QUERY_HOST "127.0.0.1"
#define QUERY_PORT 8111
 
#define SET_HOST "127.0.0.1"
#define SET_PORT 8222
 
#define MEMCACHE_HOST "127.0.0.1"
#define MEMCACHE_PORT 11211
 
#define MYSQL_HOST "127.0.0.1"
#define MYSQL_PORT 0
#define MYSQL_USER "user"
#define MYSQL_PASS "password"
#define MYSQL_DATABASE "isdup"
#define MYSQL_SOCK NULL
#define MYSQL_FLAGS 0

3. url_query.c

#include "config.h"
#include <event.h>
#include <evhttp.h>
#include <unistd.h>
#include <libmemcached/memcached.h>
 
static memcached_st *mc = NULL;
 
void init_memcache() {
    mc = memcached_create(NULL);
    memcached_server_add(mc, MEMCACHE_HOST, MEMCACHE_PORT);
}
 
void query_handler(struct evhttp_request *req, void *arg) {
   char *uri = req->uri;
 
   if (strnlen(uri, MAXLEN) == MAXLEN || *uri == '\0') {
       evhttp_connection_free(req->evcon);
       return;
   }
 
   size_t len;
   char *result;
   uint32_t flags;
   memcached_return ret;
 
   result = memcached_get(mc, uri+1, strnlen(uri+1, MAXLEN), &len, &flags, &ret);
 
   if (result) {
       evhttp_send_reply(req, HTTP_OK, "OK", NULL);
       free(result);
   }
   else {
       evhttp_send_reply(req, HTTP_NOTFOUND, "NOT FOUND", NULL);
   }
}
 
 
int main(int argc, char **argv) {
    mc = memcached_create(NULL);
    init_memcache();
 
    event_init();
    struct evhttp *httpd = evhttp_start(QUERY_HOST, QUERY_PORT);
    evhttp_set_gencb(httpd, query_handler, NULL);
    event_dispatch();
    evhttp_free(httpd);
    return 0;
}

4. url_set.c

#include "config.h"
#include <stdio.h>
#include <event.h>
#include <evhttp.h>
#include <unistd.h>
#include <libmemcached/memcached.h>
#include <mysql/mysql.h>
 
static memcached_st *mc = NULL;
static MYSQL *mysql = NULL;
static MYSQL_RES *res = NULL;
static MYSQL_ROW row;
static char buf[MAXLEN];
 
void init_memcache() {
    mc = memcached_create(NULL);
    memcached_server_add(mc, MEMCACHE_HOST, MEMCACHE_PORT);
}
 
void init_mysql() {
    if ((mysql = mysql_init(NULL)) == NULL) {
        fprintf(stderr, "mysql_init\n");
        exit(-1);
    }
    if (mysql_real_connect(
                mysql, 
                MYSQL_HOST, 
                MYSQL_USER, 
                MYSQL_PASS, 
                MYSQL_DATABASE, 
                MYSQL_PORT, 
                MYSQL_SOCK, 
                MYSQL_FLAGS
    ) == NULL) {
        fprintf(stderr, "mysql_connect[%d]: %s\n", mysql_errno(mysql), mysql_error(mysql));
        exit(-1);
    }
}
 
void set_handler(struct evhttp_request *req, void *arg) {
   char *uri = req->uri;
 
   if (strnlen(uri, MAXLEN) == MAXLEN || *uri == '\0') {
       evhttp_connection_free(req->evcon);
       return;
   }
 
   uri++;
   sprintf(buf, "SELECT url FROM url WHERE url = '%s' limit 1", uri);
   mysql_query(mysql, buf);
   res = mysql_store_result(mysql);
   if (mysql_num_rows(res)) {
       fprintf(stderr, "num_rows: %d\n", mysql_num_rows(res));
       memcached_set(mc, uri, strlen(uri), "1", 1, 0, 0); evhttp_send_reply(req, HTTP_OK, "OK", NULL); }
   else {
       evhttp_send_reply(req, HTTP_NOTFOUND, "NOT FOUND", NULL);
   }
}
 
 
int main(int argc, char **argv) {
    init_memcache();
    init_mysql();
 
    event_init();
    struct evhttp *httpd = evhttp_start(SET_HOST, SET_PORT);
    evhttp_set_gencb(httpd, set_handler, NULL);
    event_dispatch();
    evhttp_free(httpd);
    return 0;
}

5. nginx 配置

 
#user  nobody;
worker_processes  1;
 
#error_log  logs/error.log;
#error_log  logs/error.log  notice;
#error_log  logs/error.log  info;
 
#pid        logs/nginx.pid;
 
 
events {
    worker_connections  1024;
}
 
 
http {
    include       mime.types;
    default_type  application/octet-stream;
 
    upstream url_query {
        server 127.0.0.1:8111;
    }
    upstream url_set {
        server 127.0.0.1:8222;
    }
    server {
        listen       80;
        server_name  localhost;
 
        location / {
            proxy_pass http://url_query;
            proxy_set_header Host $host;
            proxy_set_header X-Real-IP $remote_addr;
            proxy_set_header X-Forwarded-For "$remote_addr";
            error_page 404 502 503 504 = @fallback;
        }
 
        location @fallback {
            proxy_pass http://url_set;
        }
    }
}

6. 测试
数据表里有一条url为aaa的记录.

[lyxint@null isdup]$ curl -I http://127.0.0.1/http://lyxint.com/
HTTP/1.1 404 NOT FOUND
Server: nginx/0.9.3
Date: Sun, 31 Jul 2011 03:54:56 GMT
Connection: keep-alive
 
[lyxint@null isdup]$ curl -I http://127.0.0.1/aaa
HTTP/1.1 200 OK
Server: nginx/0.9.3
Date: Sun, 31 Jul 2011 03:55:15 GMT
Connection: keep-alive

没有做压力测试, 用ab测来效果倒是不错, 不过不是随机的url, 不具备说服力.

7. 注意
这两个C程序写得很简单, 错误处理什么的很少, 还需要改进. 当然, 这只是一个demo
由于url存在memcached的key里, 而memcached的key最大长度为写死为250. 以防url长度超过250, 编译memcached的时候需要把memcached.h中的#define KEY_MAX_LENGTH 250改大一点

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