Monitor

Connect middleware to monitor an application process.

Installation

$ npm install connect-middleware-monitor

Usage

To use the module,

var createMonitor = require( 'connect-middleware-monitor' );

createMonitor( [...plugin] )

The middleware generator accepts monitor plugins which append to a common metrics object.

var // Plugin which reports system metrics:
	sPlugin = require( 'monitor-plugin-os' ),

	// Plugin which reports current process metrics:
	pPlugin = require( 'monitor-plugin-process' );

// Create the monitor middleware:
var monitor = createMonitor( sPlugin, pPlugin );

Note: plugins are executed in the same order as they are provided to the middleware generator.

Each plugin should be a single method which accepts two input arguments: [object, clbk]. The object is a shared object among all plugins; hence, when choosing plugins, ensure that they are properly namespaced when appending to the object.

The callback should be invoked once the plugin finishes appending metrics. The callback takes an optional error argument. Any errors are bubbled up through the middleware.

See monitor-plugin-os and monitor-plugin-process for plugin examples.

monitor( request, response, next )

The generated middleware follows the connect middleware pattern. Monitor metrics are appended to the request object via a locals property. Hence, downstream middleware consumers may access the metrics via

var metrics = request.locals.monitor;

See the examples below.

Examples

var express = require( 'express' ),
	request = require( 'request' ),
	sPlugin = require( 'monitor-plugin-os' ),
	pPlugin = require( 'monitor-plugin-process' ),
	createMonitor = require( 'connect-middleware-monitor' );

// Define a port:
var PORT = 7331;

// Create a new monitor:
var monitor = createMonitor( sPlugin, pPlugin );

// Create a new application:
var app = express();

// Bind a route using the monitor middleware:
app.get( '/', [ monitor, sendJSON ] );

// Spin up a new server:
var server = app.listen( PORT, onListen );


function onListen() {
	request({
		'method': 'GET',
		'uri': 'http://127.0.0.1:' + PORT
	}, onResponse );
}

function onResponse( error, response, body ) {
	if ( error ) {
		throw new Error( error );
	}
	console.log( body );
}

function sendJSON( request, response, next ) {
	response
		.status( 200 )
		.send( JSON.stringify( request.locals.monitor ) );
}

To run an example from the top-level application directory,

$ node ./examples/index.js

Plugins

List of monitor plugins:

• monitor-plugin-os: system-level metrics
• monitor-plugin-process: current process metrics

Tests

Unit

Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:

$ make test

All new feature development should have corresponding unit tests to validate correct functionality.

Test Coverage

This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:

$ make test-cov

Istanbul creates a ./reports/coverage directory. To access an HTML version of the report,

$ make view-cov

License

MIT license.

Copyright

Copyright © 2014. Athan Reines.