zmq-json-sub.js

A node.js module for subcribing to JSON messages via 0MQ (ZeroMQ)

Install 0MQ

On a Mac:

$ brew install zmq

To verify the installation

$ man zmq

See zeromq.org

Install zmq-json-sub in your project

$ npm init
$ npm install zmq-json-sub --save

Usage

The complete example can be found in the examples/demo folder.

This example shows how to create a simple app that subcribes to JSON messages from a publisher.

File: examples/demo/config.js

var config = {};
config.endpoint = "tcp://localhost:5431";
module.exports = config; 

File: examples/demo/index.js

"use strict";

var ZmqJsonSub = require('zmq-json-sub'),
	config = require('./config'),
	sub = null;

var spec = {
	endpoint: config.endpoint, 
	filter: "", 
	onMessage: function (data) {
    	let jstring = JSON.parse(data);
    	console.log( jstring );
    	if (jstring.timestamp) {
        	console.log( "TIME STAMP: [" 
            	+ new Date(jstring.timestamp) 
            	+ "]");
    	}
	}
};

sub = new ZmqJsonSub(spec, function(err, data) {
	if (err) {
    	console.log(err);
    	return;
	}
});

console.log("Subscribed to: " + config.endpoint);

/*
	Handle termination - close sub.
*/

//  terminator === the termination handler.
function terminator(sig) {
	if (typeof sig === "string") {
	  	console.log('%s: Received %s - terminating Node server ...',
    		Date(Date.now()), sig);
  		console.log("Closing subcriber before exit");
  		sub.close();
  		process.exit(1);
	}
	console.log('%s: Node server stopped.', Date(Date.now()) );
}	

//  Process on exit and signals.
process.on('exit', function() { terminator(); });

['SIGHUP', 'SIGINT', 'SIGQUIT', 'SIGILL', 'SIGTRAP', 'SIGABRT', 'SIGBUS',
 'SIGFPE', 'SIGUSR1', 'SIGSEGV', 'SIGUSR2', 'SIGPIPE', 'SIGTERM'
].forEach(function(element, index, array) {
	process.on(element, function() { terminator(element); });
});

To run:

$ node index.js

To stop press Ctrl-C.

To test with some messages see the example/demo project in the companion project https://www.npmjs.com/package/zmq-json-pub. Run the subscriber demo in one terminal window and the publisher demo in another. The subscriber should log to the console messages generated by the publisher.

Tests

Tests assume that mocha has been installed globally. If not execute the following:

$ npm install -g mocha

Run the tests from the projects root folder in one of the following ways:

$ mocha --recursive --timeout 20000

Or

$ npm test

Or if you feel like kickin' it old skool:

make test

Testing by Version

To run the tests for each version (currently there is only one version (v0001)):

$ mocha --timeout 5000 --recursive test/v0001/*test.js

The tests generate log files in a logs/ folder under the projects root folder.

Repo(s)

• bitbucket.org/mitchallen/zmq-json-sub.git

Contributing

In lieu of a formal style guide, take care to maintain the existing coding style. Add unit tests for any new or changed functionality. Lint and test your code.

Version History

Version 0.1.1 release notes

• Updated demo to use live module

Version 0.1.0 release notes

• Initial release