nginx如何限制搜索引擎爬虫频率与屏蔽网络爬虫？

#全局配置
limit_req_zone $anti_spider zone=anti_spider:10m rate=15r/m;
#某个server中
 limit_req zone=anti_spider burst=30 nodelay;
 if ($http_user_agent ~* "xxspider|xxbot") {
 set $anti_spider $http_user_agent;
}
 

server { 
        listen       80; 
        server_name  www.xxx.com; 
 
        #charset koi8-r; 
 
        #access_log  logs/host.access.log  main; 
 
        #location / { 
        #    root   html; 
        #    index  index.html index.htm; 
        #} 
    if ($http_user_agent ~* "qihoobot|Baiduspider|Googlebot|Googlebot-Mobile|Googlebot-Image|Mediapartners-Google|Adsbot-Google|Feedfetcher-Google|Yahoo! Slurp|Yahoo! Slurp China|YoudaoBot|Sosospider|Sogou spider|Sogou web spider|MSNBot|ia_archiver|Tomato Bot") { 
                return 403; 
        } 
 
    location ~ ^/(.*)$ { 
                proxy_pass http://localhost:8080; 
        proxy_redirect          off; 
        proxy_set_header        Host $host; 
        proxy_set_header        X-Real-IP $remote_addr; 
        proxy_set_header       X-Forwarded-For   $proxy_add_x_forwarded_for; 
        client_max_body_size    10m; 
        client_body_buffer_size 128k; 
        proxy_connect_timeout   90; 
        proxy_send_timeout      90; 
        proxy_read_timeout      90; 
        proxy_buffer_size       4k; 
        proxy_buffers           4 32k; 
        proxy_busy_buffers_size 64k; 
        proxy_temp_file_write_size 64k; 
    } 
     
        #error_page  404              /404.html; 
 
        # redirect server error pages to the static page /50x.html 
        # 
        error_page   500 502 503 504  /50x.html; 
        location = /50x.html { 
            root   html; 
        } 
 
        # proxy the PHP scripts to apache listening on 127.0.0.1:80 
        # 
        #location ~ .php$ { 
        #    proxy_pass   http://127.0.0.1; 
        #} 
 
        # pass the PHP scripts to fastcgi server listening on 127.0.0.1:9000 
        # 
        #location ~ .php$ { 
        #    root           html; 
        #    fastcgi_pass   127.0.0.1:9000; 
        #    fastcgi_index  index.php; 
        #    fastcgi_param  SCRIPT_FILENAME  /scripts$fastcgi_script_name; 
        #    include        fastcgi_params; 
        #} 
 
        # deny access to .htaccess files, if Apache's document root  
        # concurs with nginx's one 
        # 
        #location ~ /.ht { 
        #    deny  all; 
        #} 
    }