node-shutdown-manager

The node shutdown manager manages a chain of functions to be executed when the application is shutting down. This manager allows both synchronous and asynchronous functions to be added, and only complete the shutdown process once the functions have finished executing.

This can be extremely helpful if you need to perform a few actions to cleanup your application before exiting.

Install

npm install node-shutdown-manager

API

You can create an instance of the shutdown manager by calling the createShutdownManager method.

var shutdownManager = require('node-shutdown-manager').createShutdownManager();

Once created, you can add a method to the shutdown action chain by simply calling the addShutdownAction method. This method will accept a function. The function must not require any arguments.

manager.addShutdownAction(sampleFunction);

Additionally you can use the addFinalShutdownAction method. This method is identical to addShutdownAction BUT it these methods are executed only after all the addShutdownAction promises are fulfilled. This allows you to delay shutdown of some components (such as loggers) so that they are available until all the components shutdown.

Asynchronous Functions

You can add asynchronous functions to the action chain as long as they return a promise (that conforms to CommonJS Promises/A). I would recommend using Q if you are looking for a library that supports the promise spec.

var async1Function = function() {
	var deferred = q.defer();
	setTimeout(function() {
		console.log("Async Action 1 Completed");
		deferred.resolve();
	}, 1000);
	return deferred.promise;
};
manager.addShutdownAction(async1Function);

Customizing Logging

One aspect of customization with the manager is how it handles logging. You can pass in any object as a custom logger as long as it has a log function with accepts the log message as an argument. In addition, you can pass in a custom logging prefix (there is one used by default).

var shutdownManager = require('node-shutdown-manager').createShutdownManager({
	logger: customLogger,
	loggingPrefix: "[Custom Logging Prefix]: "
});

Timeout

Set a configuration setting of 'timeout' in milliseconds to limit how long the manager waits for promises to be fulfilled.

var shutdownManager = require('node-shutdown-manager').createShutdownManager({
	timeout: 10000 // Limit async shutdown promises to 10 seconds to execute
});

Events

• Event 'preShutdown' calls a method with the arguments (reason, err). If no listener is specified, the default action is to log the received event. Reason will be SIGINT, TERM, exit, or uncaughtException.

• Event 'shutdownActionException' is emitted if an exception is thrown out of a shutdown action. Function is passed (err, method). If no listener is specified, the default action is to log the received event.

• Event 'shutdownComplete' is emitted once the shutdown actions are all executed. Function is passed (exitCode, errors). If no listener is specified, the default action is to log and call process.exit. WARNING: If you register a listener to this event, you are responsible for calling Process.exit() This allows the caller to alter exit codes or other details about the exit.

var shutdownManager = require('node-shutdown-manager').createShutdownManager({});
shutdownManager.on('preShutdown', function( reason, err) {
    log.console("Shutting down for: "+reason);
    log.console("Error: "+err.stack || err);
});
shutdownManager.on('shutdownActionException', function(err, method) {
    log.console("Error in shutdown action being ignored:");
    log.console("Error: "+err.stack || err);
});
shutdownManager.on('shutdownComplete', function(err, method) {
    log.console("Shutdown actions complete");
    log.console("Error: "+err.stack || err);
    process.exit(0); // For example, if you never want to exit with an error code
});

Shutdown Process

The manager detects the following situations:

• When your application is shutting down due to the SIGINT signal (for example when you press CTRL+C).
• When your application is shutting down due to the SIGTERM signal (when closed by the operating system or managing process).
• When your application is shutting down due to an uncaught exception.

It is important to know that other situations will cause the manager not to function. For example, if your application is force closed (by receiving the SIGKILL signal), then the shutdown manager will not be executed.

License

Copyright 2013 David Tucker All rights reserved.

The software is licensed under an MIT License:

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.