本文主要解析一下ngx_http_core_module、ngx_http_limit_conn_module以及ngx_http_limit_req_module中的limit相关配置参数。

limit_rate

名称 默认配置 作用域 官方说明 中文解读 模块 limit_rate limit_rate 0; http, server, location, if in location Limits the rate of response transmission to a client. The rate is specified in bytes per second. The zero value disables rate limiting. The limit is set per a request, and so if a client simultaneously opens two connections, the overall rate will be twice as much as the specified limit. 指定每秒该连接能下载的bytes,主要用来限制个别请求的带宽 ngx_http_core_module limit_rate_after limit_rate_after 0; http, server, location, if in location Sets the initial amount after which the further transmission of a response to a client will be rate limited. 设置多少bytes过后将启动limit计数,如果小于此值则不限速 ngx_http_core_module limit_except 没有默认值 location Limits allowed HTTP methods inside a location. The method parameter can be one of the following: GET, HEAD, POST, PUT, DELETE, MKCOL, COPY, MOVE, OPTIONS, PROPFIND, PROPPATCH, LOCK, UNLOCK, or PATCH. Allowing the GET method makes the HEAD method also allowed 设置除了指定的http methods外其他method将被限制，允许GET就自动允许HEAD方法 ngx_http_core_module

实例

 location /downloads {
      limit_rate_after 1m;
      limit_rate 500k;
    }

    location / {
      proxy_pass http://localhost:3000;
      limit_except GET {
        deny all;
      }
    }

limit_conn

名称 默认配置 作用域 官方说明 中文解读 模块 limit_conn 没有默认值,语法 limit_conn zone number; http, server, location Sets the shared memory zone and the maximum allowed number of connections for a given key value. When this limit is exceeded, the server will return the error in reply to a request. 指定一个zone的每个key最大连接数 ngx_http_limit_conn_module limit_conn_zone 没有默认值,语法 limit_conn_zone key zone=name:size; http Sets parameters for a shared memory zone that will keep states for various keys. In particular, the state includes the current number of connections. The key can contain text, variables, and their combination. Requests with an empty key value are not accounted. 第一个参数是key,第二个参数是指定zone及其存放元数据(key,current num of conns per key,zone size)的共享内存大小 ngx_http_limit_conn_module limit_conn_log_level limit_conn_log_level error; http, server, location Sets the desired logging level for cases when the server limits the number of connections. This directive appeared in version 0.8.18. 指定当触发limit的时候日志打印级别 ngx_http_limit_conn_module

实例

http {
  limit_conn_zone $binary_remote_addr zone=ips:10m;
  limit_conn_zone $server_name zone=servers:10m;
  limit_conn_log_level notice;
  server {
    # these limits apply to the whole virtual server
    limit_conn ips 10;

    # only 1000 simultaneous connections to the same server_name
    limit_conn servers 1000;
  }
}

limit_req

名称 默认配置 作用域 官方说明 中文解读 模块 limit_req 没有默认值,语法 limit_req zone=name [burst=number] [nodelay]; http, server, location Sets the shared memory zone and the maximum burst size of requests. If the requests rate exceeds the rate configured for a zone, their processing is delayed such that requests are processed at a defined rate. Excessive requests are delayed until their number exceeds the maximum burst size in which case the request is terminated with an error. 指定zone的burst大小 ngx_http_limit_req_module limit_req_zone 没有默认值,语法 limit_req_zone key zone=name:size rate=rate; http Sets parameters for a shared memory zone that will keep states for various keys. In particular, the state stores the current number of excessive requests. The key can contain text, variables, and their combination. Requests with an empty key value are not accounted. 第一个参数指定key,第二个参数指定zone名称和元数据的内存大小,第三个参数rate指定单位时间的请求数阈值 ngx_http_limit_req_module limit_req_log_level limit_req_log_level error; http, server, location Sets the desired logging level for cases when the server refuses to process requests due to rate exceeding, or delays request processing. Logging level for delays is one point less than for refusals. 指定触发req limit时打印的日志级别 ngx_http_limit_req_module

实例

http {
 limit_req_zone $binary_remote_addr zone=myreqzone:10m
 limit_req_log_level warn;
 server {
  ## 每个ip限定10个连接数
  ## 正常一个浏览器给每个host开两到三个连接
  ## 触发的话会返回503
  ## nodelay表示一上来就直接计算,不经过一些预热后再计算
  limit_req zone=myreqzone burst=10 nodelay;
 }
}

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