websocket-nats

An in-browser websocket client for NATS, a lightweight, high-performance cloud native messaging system.

Installation

NPM

npm install websocket-nats

CDN

Normal, development, and minified versions of the bundle can obtained via RawGit.

<script type="text/javascript" src="https://cdn.rawgit.com/isobit/websocket-nats/master/dist/websocket-nats.js"></script>

Development (includes eval sourcemaps):

<script type="text/javascript" src="https://cdn.rawgit.com/isobit/websocket-nats/master/dist/websocket-nats.dev.js"></script>

Minified (for production use):

<script type="text/javascript" src="https://cdn.rawgit.com/isobit/websocket-nats/master/dist/websocket-nats.min.js"></script>

Prerequisites

You will need a Websocket-to-TCP proxy to connect to your gnatsd instance over websockets. You may provide your own or use ws-tcp-relay.

Basic Usage

Usage is the same as node-nats, but a url to your websocket/TCP proxy should be provided instead of one pointing directly at your gnatsd instance.

var nats = require('websocket-nats').connect('ws://localhost:4223');

// Simple Publisher
nats.publish('foo', 'Hello World!');

// Simple Subscriber
nats.subscribe('foo', function(msg) {
  console.log('Received a message: ' + msg);
});

// Unsubscribing
var sid = nats.subscribe('foo', function(msg) {});
nats.unsubscribe(sid);

// Request Streams
var sid = nats.request('request', function(response) {
  console.log('Got a response in msg stream: ' + response);
});

// Request with Auto-Unsubscribe. Will unsubscribe after
// the first response is received via {'max':1}
nats.request('help', null, {'max':1}, function(response) {
  console.log('Got a response for help: ' + response);
});

// Replies
nats.subscribe('help', function(request, replyTo) {
  nats.publish(replyTo, 'I can help!');
});

// Close connection
nats.close();

Wildcard Subscriptions

// "*" matches any token, at any level of the subject.
nats.subscribe('foo.*.baz', function(msg, reply, subject) {
  console.log('Msg received on [' + subject + '] : ' + msg);
});

nats.subscribe('foo.bar.*', function(msg, reply, subject) {
  console.log('Msg received on [' + subject + '] : ' + msg);
});

// ">" matches any length of the tail of a subject, and can only be
// the last token E.g. 'foo.>' will match 'foo.bar', 'foo.bar.baz',
// 'foo.foo.bar.bax.22'
nats.subscribe('foo.>', function(msg, reply, subject) {
  console.log('Msg received on [' + subject + '] : ' + msg);
});

Queue Groups

// All subscriptions with the same queue name will form a queue group.
// Each message will be delivered to only one subscriber per queue group,
// queuing semantics. You can have as many queue groups as you wish.
// Normal subscribers will continue to work as expected.
nats.subscribe('foo', {'queue':'job.workers'}, function() {
  received += 1;
});

Clustered Usage

var nats = require('websocket-nats');

var servers = ['ws://nats.io:4222', 'ws://nats.io:5222', 'ws://nats.io:6222'];

// Randomly connect to a server in the cluster group.
var nc = nats.connect({'servers': servers});

// currentServer is the URL of the connected server.
console.log("Connected to " + nc.currentServer.host);

// Preserve order when connecting to servers.
nc = nats.connect({'dontRandomize': true, 'servers':servers});

TLS

TLS is currently not supported. You'll have to configure your websocket/TCP proxy to use TLS properly.

Secure Websockets

Connections can be made to secure websockets by using the wss protocol in the url passed to NATS.connect:

NATS.connect('wss://user:pass@localhost:4223');

Advanced Usage

// Publish with closure, callback fires when server has processed the message
nats.publish('foo', 'You done?', function() {
  console.log('msg processed!');
});

// Flush connection to server, callback fires when all messages have
// been processed.
nats.flush(function() {
  console.log('All clear!');
});

// If you want to make sure NATS yields during the processing
// of messages, you can use an option to specify a yieldTime in ms.
// During the processing of the inbound stream, we will yield if we
// spend more then yieldTime milliseconds processing.
var nc = nats.connect({port: PORT, yieldTime: 10});

// Timeouts for subscriptions
var sid = nats.subscribe('foo', function() {
  received += 1;
});

// Timeout unless a certain number of messages have been received
nats.timeout(sid, timeout_ms, expected, function() {
  timeout = true;
});

// Auto-unsubscribe after MAX_WANTED messages received
nats.subscribe('foo', {'max':MAX_WANTED});
nats.unsubscribe(sid, MAX_WANTED);

// Multiple connections
var nats = require('websocket-nats');
var nc1 = nats.connect();
var nc2 = nats.connect();

nc1.subscribe('foo');
nc2.publish('foo');

// Encodings

// By default messages received will be decoded using UTF8. To change that,
// set the encoding option on the connection.

nc = nats.connect({'servers':servers, 'encoding': 'ascii'});

See examples and benchmarks for more information..

License

(The 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.

isobit / websocket-nats