How to set the maximum number of connections in nodejs

Node.js is an event-driven server-side JavaScript runtime environment suitable for developing high-performance, scalable network applications. In practical applications, we often need to implement concurrent network connection management of the server by writing Node.js applications. However, in the process of connection management, we may encounter the problem of bottlenecks caused by too many connections, so we need to set the maximum number of connections for Node.js.

Node.js is a single-threaded event-driven program and uses asynchronous I/O to handle network requests. This means that Node.js can handle many concurrent connections at the same time. Under the default settings of Node.js, there is no limit on the maximum number of connections, which is no problem for most applications. However, in some cases, we need to limit the maximum number of connections to avoid excessive occupation of server resources.

There are many ways to set the maximum number of connections in Node.js. Let’s introduce them one by one below.

Method 1: Use the ulimit command

The ulimit command is a tool under Linux/Unix systems that is used to limit the resource usage of user programs. By modifying the value of the ulimit command, you can limit the maximum number of Node.js connections. In the command line terminal, you can use the following command to set the maximum number of connections for Node.js:

ulimit -n 1000

The maximum number of connections is set to 1000. Of course, you can also adjust it according to your needs.

Method 2: Modify the Node.js source code

Another way to set the maximum number of Node.js connections is to modify the Node.js source code. The prerequisite for doing this is that we need to master the source code structure of Node.js and how to compile the modified version. The specific modification steps are as follows:

1. Open the lib/internal/socket_list.js file in the Node.js source directory.
2. In the 18th line of code, find the following code:

const MAX_SOCKETS = Infinity;

3. Change the Infinity in the above code to the maximum number of connections you want to set, for example:

const MAX_SOCKETS = 1000;

The maximum number of connections is set to 1000. Likewise, you can adjust it to suit your needs.

4. Recompile the Node.js source code and replace the original Node.js executable file in the system.

Method 3: Using Node.js module

Another way to set the maximum number of connections in Node.js is to use a third-party module. The more popular modules currently are ulimit and limitation. Both modules are used to limit the resource usage of the process, including the maximum number of file descriptors, maximum memory usage, etc. Using these two modules, you can easily set the maximum number of connections in your Node.js application.

Usage example of ulimit module:

const ulimit = require('ulimit');

ulimit.set({nofile: 1000}, (err, res) => {
    if (err) {
        console.error(`Failed to set ulimit: ${err}`);
        return;
    }
    console.log(`Set ulimit: ${res}`);
});

The maximum number of connections is set to 1000, which is the same as the previous two methods.

Usage example of the limitation module:

const limitation = require('limitation');

limitation.set('nofile', 1000)
    .then(() => console.log('Set maximum number of file descriptors to 1000'))
    .catch((err) => console.error(err));

The maximum number of connections is also set to 1000 here.

The above are three methods for setting the maximum number of connections in Node.js. Either method allows us to more flexibly manage the number of network connections for Node.js applications, thereby avoiding excessive occupation of server resources and improving application performance and stability.

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