flash-oss/lil-http-terminator

Zero dependencies, gracefully terminates HTTP(S) server.

lil-http-terminator 🦾

Gracefully terminates HTTP(S) server.

This module was forked from the amazing http-terminator. The important changes:

• Zero dependencies, 11 KB on your disk. The original http-terminator brings in more than 20 sub-dependencies, >450 files, 2 MB total.
• Removed TypeScript and a dozen of supporting files, configurations, etc. No more code transpilation.
• Simpler API. Now you do require("lil-http-terminator")({ server }); to get a terminator object.
• The termination never throws. You don't want to handle unexpected exceptions during your server shutdown.
• Termination won't hang forever if server never closes the port because some browsers disrespect connection:close header.

Behaviour

When you call server.close(), it stops the server from accepting new connections, but it keeps the existing connections open indefinitely. This can result in your server hanging indefinitely due to keep-alive connections or because of the ongoing requests that do not produce a response. Therefore, in order to close the server, you must track creation of all connections and terminate them yourself.

lil-http-terminator implements the logic for tracking all connections and their termination upon a timeout. lil-http-terminator also ensures graceful communication of the server intention to shutdown to any clients that are currently receiving response from this server.

API

const HttpTerminator = require("lil-http-terminator");

const terminator = HttpTerminator({
    server, // required. The node.js http server object instance
    
    // optional
    gracefulTerminationTimeout: 1000, // optional, how much time we give "keep-alive" connections to close before destryong them
    maxWaitTimeout: 30000, // optional, termination will return {success:false,code:"TIMED_OUT"} if it takes longer than that
    logger: console, // optional, default is `global.console`. If termination goes wild the module might log about it using `logger.warn()`.
});

// Do not call server.close(); Instead call this:
const { success, code, message, error } = await terminator.terminate();
if (!success) {
    if (code === "TIMED_OUT") console.log(message); 
    if (code === "SERVER_ERROR") console.error(message, error); 
    if (code === "INTERNAL_ERROR") console.error(message, error); 
}

Usage

Use the terminator when node.js process is shutting down.

const http = require("http");

const server = http.createServer();

const httpTerminator = require("lil-http-terminator")({ server });

async function shutdown(signal) {
    console.log(`Received ${signal}. Shutting down.`)
    const { success, code, message, error } = await httpTerminator.terminate();
    console.log(`HTTP server closure result: ${success} ${code} ${message} ${error || ""}`);
    process.exit(0);
}

process.on("SIGTERM", shutdown); // used by K8s, AWS ECS, etc.
process.on("SIGINT", shutdown); // Atom, VSCode, WebStorm or Terminal Ctrl+C

Alternative libraries

There are several alternative libraries that implement comparable functionality, e.g.

• https://github.com/gajus/http-terminator (origin of this module)
• https://github.com/hunterloftis/stoppable
• https://github.com/thedillonb/http-shutdown
• https://github.com/tellnes/http-close
• https://github.com/sebhildebrandt/http-graceful-shutdown

The main benefit of lil-http-terminator is that:

• it does not have any dependencies
• it never throws any errors but resolves an object: {success:Boolean, code:String, message:String, error?:Error}.
• it never hangs if server can't be closed because of bad browser behaviour. Returns {success:false,code:"TIMED_OUT"}.
• it does not monkey-patch Node.js API
• it immediately destroys all sockets without an attached HTTP request
• it allows graceful timeout to sockets with ongoing HTTP requests
• it properly handles HTTPS connections
• it informs connections using keep-alive that server is shutting down by setting a connection: close header
• it does not terminate the Node.js process

FAQ

What is the use case for lil-http-terminator?

To gracefully terminate a HTTP server.

We say that a service is gracefully terminated when service stops accepting new clients, but allows time to complete the existing requests.

There are several reasons to terminate services gracefully:

• Terminating a service gracefully ensures that the client experience is not affected (assuming the service is load-balanced).
• If your application is stateful, then when services are not terminated gracefully, you are risking data corruption.
• Forcing termination of the service with a timeout ensures timely termination of the service (otherwise the service can remain hanging indefinitely).