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Creating an Agent in Node.js
You can use new Agent() method to create an instance of an agent in Node. The http.request() method uses the globalAgent from the 'http' module to create a custom http.Agent instance.
Syntax
new Agent({options})Parameters
The above function can accept the following Parameters −
options – These options will contain the configurable options that could be set on an Agent while creation. Below are the fields/options the Agent can have −
keepAlive – This method keeps the sockets around whether there are any outstanding requests or not, but keeps them for any future requests without actually re-establishing the TCP connection. One can use 'close' connection' to close this connection. Default value: false.
keepAliveMsecs – On using the keepAlive option as true, this option defines the initial delay for TCP keep-Alive packets. Default value is 1000.
maxSockets – This options defines the maximum number of sockets that are allowed per host. By Default this value is infinity.
maxTotalSockets – Total number of sockets that are allowed for all the hosts. Each requests uses a new socket until the limit is reached. Default value is Infinity.
maxFreeSockets - This is the maximum number of free sockets that can be left open in a free state. Default value is: 256.
scheduling – This is the scheduling strategy that can be applied while picking the next free socket to use. The scheduling can either be 'fifo' or 'lifo'.
timeout – Represents socket timeout in milliseconds.
Example
Create a file with name – agent.js and copy the below code snippet. After creating file, use the following command to run this code as shown in the example below −
node agent.js
agent.js
// Node.js program to demonstrate the creation of new Agent
// Importing the http module
const http = require('http');
// Creating a new agent
var agent = new http.Agent({});
// Defining options for agent
const aliveAgent = new http.Agent({
keepAlive: true, maxSockets: 5,
});
// Creating connection with alive agent
var aliveConnection = aliveAgent.createConnection;
// Creating new connection
var connection = agent.createConnection;
// Printing the connection
console.log('Succesfully created connection with agent: ',
connection.toString);
console.log('Succesfully created connection with alive agent: ',
aliveConnection.toString);Output
C:\home
ode>> node agent.js Succesfully created connection with agent: function toString() { [native code] } Succesfully created connection with alive agent: function toString() { [native code] }
Example
The 'agentkeepalive' module provides better flexibility while trying to create a socket or agent. We will use this module in the below example for better understanding.
Installation
npm install agentkeepalive --save
Program Code
// Node.js program to demonstrate the creation of new Agent
// Importing the http module
const http = require('http');
// Importing the agentkeepalive module
const Agent = require('agentkeepalive');
// Creating a new agent
const keepAliveAgent = new Agent({});
// Implementing some options
const options = {
host: 'tutorialspoint.com',
port: 80,
path: '/',
method: 'GET',
agent: keepAliveAgent,
};
// Requesting details via http server module
const req = http.request(options, (res) => {
// Printing statuscode, headers and other details
// received from the request
console.log("StatusCode: ", res.statusCode);
console.log("Headers: ", res.headers);
});
// Printing the agent options
console.log("Agent Options: ", req.agent.options);
req.end();Output
C:\home
ode>> node agent.js Agent Options: { socketActiveTTL: 0, timeout: 30000, freeSocketTimeout: 15000, keepAlive: true, path: null } StatusCode: 403 Headers: { date: 'Sun, 25 Apr 2021 08:21:14 GMT', server: 'Apache', 'x-frame-options': 'SAMEORIGIN', 'last-modified': 'Thu, 16 Oct 2014 13:20:58 GMT', etag: '"1321-5058a1e728280"', 'accept-ranges': 'bytes', 'content-length': '4897', 'x-xss-protection': '1; mode=block', vary: 'User-Agent', 'keep-alive': 'timeout=5, max=100', connection: 'Keep-Alive', 'content-type': 'text/html; charset=UTF-8' }
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