Node.js初步-API-Http.md

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• Node.js初步 - API - Http
  • Http 初步
  • Http Class
    • http.Agent

Node.js初步 - API - Http

Http 初步

var http = require('http')

HTTP message headers are represented by an object like this. Keys are lowercased. Values are not modified.

http 头部信息通畅是如下所示的对象。Key全部小写，值是不能修改的

{ 
  'content-length': '123',
  'content-type': 'text/plain',
  'connection': 'keep-alive',
  'host': 'mysite.com',
  'accept': '*/*' 
}

In order to support the full spectrum of possible HTTP applications, Node.js's HTTP API is very low-level. It deals with stream handling and message parsing only.

为了能全面地支持可能的HTTP应用程序，Node提供的HTTP API都很底层。它处理的只有流处理和消息解析。

It parses a message into headers and body but it does not parse the actual headers or the body.

它把一份消息解析成报文头和报文体，但是它不解析实际的报文头和报文体。

接收到的原始头信息以数组形式 [key, value, key2, value2, ...] 保存在 rawHeaders 属性中. 例如, 前面提到的消息对象会有 rawHeaders 列表如下

[ 'ConTent-Length', '123456',
  'content-LENGTH', '123',
  'content-type', 'text/plain',
  'CONNECTION', 'keep-alive',
  'Host', 'mysite.com',
  'accepT', '*/*' ]

Http Class

http.Agent

HTTP Agent 是用于把套接字做成资源池，用于HTTP客户端请求

HTTP Agent 也把客户端的请求默认为使用 Connection:keep-alive

Sockets are removed from the agent's pool when the socket emits either a 'close' event or a special 'agentRemove' event. This means that if you intend to keep one HTTP request open for a long time and don't want it to stay in the pool you can do something along the lines of:

http.get(options, (res) => {
  // Do stuff
}).on('socket', (socket) => {
  socket.emit('agentRemove');
});

Alternatively, you could just opt out of pooling entirely using agent:false :

http.get({
  hostname: 'localhost',
  port: 80,
  path: '/',
  agent: false  // create a new agent just for this one request
}, (res) => {
  // Do stuff with response
})

new Agent([options]):

• options
  • keepAlive Boolean Keep sockets around in a pool to be used by other requests in the future. Default = false
  • keepAliveMsecs Integer When using HTTP KeepAlive, how often to send TCP KeepAlive packets over sockets being kept alive. Default = 1000. Only relevant if keepAlive is set to true.
  • maxSockets Number Maximum number of sockets to allow per host. Default = Infinity
  • maxFreeSockets Number Maximum number of sockets to leave open in a free state. Only relevant if keepAlive is set to true. Default = 256

To configure any of them, you must create your own http.Agent object.

const http = require('http');
var keepAliveAgent = new http.Agent({ keepAlive: true });
options.agent = keepAliveAgent;
http.request(options, onResponseCallback);