new Agent() Method in Node.js

Introduction to http.Agent in Node.js

In Node.js, the http.Agent class plays a pivotal role in managing connection persistence and reuse for HTTP clients. By creating a new instance using new Agent(), developers can fine-tune how HTTP requests are handled, optimizing performance and resource utilization.

Why Use a Custom Agent?

While Node.js provides a default global agent, there are scenarios where customizing an agent becomes beneficial:

• Controlling the number of concurrent sockets.
• Enabling persistent connections with keepAlive.
• Managing socket timeouts and scheduling strategies.

Creating a New Agent

To instantiate a new HTTP agent:

const http = require('http');

const agent = new http.Agent({
  keepAlive: true,
  maxSockets: 5,
  timeout: 60000
});

In this example:

• keepAlive: true ensures sockets are reused for multiple requests.
• maxSockets: 5 limits the number of concurrent sockets per host.
• timeout: 60000 sets the socket timeout to 60 seconds.

Key Configuration Options

When creating a new agent, several options can be configured:

• keepAlive (boolean): Determines whether to keep sockets around for future requests. Default is false.
• keepAliveMsecs (number): Sets the initial delay for TCP Keep-Alive packets. Default is 1000.
• maxSockets (number): Maximum number of sockets per host. Default is Infinity.
• maxTotalSockets (number): Maximum number of sockets across all hosts. Default is Infinity.
• maxFreeSockets (number): Maximum number of sockets to leave open in a free state. Default is 256.
• scheduling (string): Strategy for selecting the next socket to use. Options are 'fifo' (default) or 'lifo'.
• timeout (number): Socket timeout in milliseconds. Default is undefined.

Using the Agent with HTTP Requests

Once an agent is created, it can be used with HTTP requests to manage connections:

const options = {
  hostname: 'example.com',
  port: 80,
  path: '/',
  method: 'GET',
  agent: agent
};

const req = http.request(options, (res) => {
  // Handle response
});

req.end();

By specifying the custom agent in the request options, the HTTP client will utilize the configured settings for connection management.

Best Practices

When working with custom agents:

• Always destroy the agent when it's no longer needed to free up resources.
• Monitor socket usage to prevent resource exhaustion.
• Adjust configuration options based on the specific needs of your application.

Conclusion

The new Agent() method in Node.js provides developers with the tools to manage HTTP connections effectively. By customizing agent settings, applications can achieve better performance, resource management, and scalability.