index.js

"use strict";
var fs = require("fs");

var status = 500;
var toobusy = false;
var stopping = false;

function setStatus(code) {
	if (!Number.isInteger(code) || code < 1 || code > 999) {
		var e = new Error("status should be an integer between 1 and 999");
		e.status = code;
		throw e;
	}
	status = code;
}

function getStatus() {
	return status;
}

/**
 * returns 503 if server is toobusy, status (as defined by setStatus) otherwise.
 */
function route(req, res) {
	if (toobusy && toobusy()) {
		res.sendStatus(503).end();
	} else {
		res.sendStatus(status).end();
	}
}

/**
 * adds a `Connection: close` to all responses if app.get('stopping') is true.
 */
function gracefulShutdownKeepaliveConnections(req, res, next) {
	if (stopping === true) {
		res.set("Connection", "close");
	}
	next();
}

function enableTooBusy(lag) {
	if (typeof lag === "undefined") {
		lag = 70;
	}
	if (!Number.isInteger(lag) || lag < 10) {
		var e = new Error("lag should be an integer greater than 10");
		e.lag = lag;
		throw e;
	}
	toobusy = require("toobusy-js");
	toobusy.maxLag(lag);
}

/**
 * - logs shutdown to graylog (if log4js logger provided).
 * - sets `stopping` to true.
 * - dumps error in terminationFile if provided.
 */
function shutdown(signal, error, cb, terminationFile, logger) {
	status = 503;
	var reason;
	if (error) {
		if (logger && logger.fatal) {
			let uError = {};
			const errorKeys = Object.keys(error);
			for (let index = 0; index < errorKeys.length; index++) {
				const key = errorKeys[index];
				uError[`_${key}`] = error[key];
			}
			logger.fatal(
				{ GELF: true, _signal: signal, _stack: error.stack, ...uError },
				error.message
			);
		}
		reason = `${signal}\n${error.message}\n${error.stack}`;
	} else {
		if (logger && logger.info) {
			logger.info({ GELF: true, _signal: signal }, "shutdown");
		}
		reason = "shutdown";
	}
	if (stopping === true) {
		return;
	}
	stopping = true;

	function callback() {
		if (cb) {
			return cb(signal ? 1 : 0);
		}
	}

	if (terminationFile) {
		fs.writeFile(terminationFile, reason, function (err) {
			if (err) {
				console.error(err);
			}
			callback();
		});
	} else {
		callback();
	}
}

module.exports = {
	setStatus: setStatus,
	getStatus: getStatus,
	route: route,
	shutdown: shutdown,
	enableTooBusy: enableTooBusy,
	gracefulShutdownKeepaliveConnections: gracefulShutdownKeepaliveConnections,
};