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# mqlobber [](https://travis-ci.org/davedoesdev/mqlobber) [](https://ci.appveyor.com/project/davedoesdev/mqlobber) [](https://coveralls.io/r/davedoesdev/mqlobber?branch=master) [](http://badge.fury.io/js/mqlobber)
Streaming message queue with pub-sub, work queues, wildcards and back-pressure.
Just Node and a filesystem required.
`mqlobber` basically remotes
[`qlobber-fsq`](https://github.com/davedoesdev/qlobber-fsq) over one or more
connections.
<p align="center"><img src="http://rawgit.davedoesdev.com/davedoesdev/mqlobber/master/diagrams/overview.svg" width="80%"/></p>
Say you have a server and a number of clients, with the clients
connected to the server using some mechanism which provides a stream for each
connection. Create a `QlobberFSQ` instance on the server and for each stream,
pass the instance and the stream to `MQlobberServer`.
On each client, pass the other end of the stream to `MQlobberClient`. Clients
can then publish and subscribe to topics (including wildcard subscriptions).
Work queues are also supported - when publishing a message, a client can specify
that only one subscriber should receive it.
All data is transferred on streams multiplexed over each connection using
[`bpmux`](https://github.com/davedoesdev/bpmux), with full back-pressure support
on each stream. Clients get a `Writable` when publishing a message and a
`Readable` when receiving one.
You can scale out horizontally by creating a number of `QlobberFSQ` instances
(e.g. one per CPU core), all sharing the same message directory.
<p align="center"><img src="http://rawgit.davedoesdev.com/davedoesdev/mqlobber/master/diagrams/multi_instance.svg" width="80%"/></p>
No other backend services are required - just Node and a filesystem.
The API is described [here](#api).
## Example
First, let's create a server program which listens on a TCP port specified on
the command line:
```javascript
// server.js
var net = require('net'),
QlobberFSQ = require('qlobber-fsq').QlobberFSQ,
MQlobberServer = require('mqlobber').MQlobberServer,
fsq = new QlobberFSQ();
fsq.on('start', function ()
{
var server = net.createServer().listen(parseInt(process.argv[2]));
server.on('connection', function (c)
{
new MQlobberServer(fsq, c);
});
});
```
Next, a program which connects to the server and subscribes to messages
published to a topic:
```javascript
// client_subscribe.js
var assert = require('assert'),
MQlobberClient = require('mqlobber').MQlobberClient,
c = require('net').createConnection(parseInt(process.argv[2])),
mq = new MQlobberClient(c),
topic = process.argv[3];
mq.subscribe(topic, function (s, info)
{
var msg = '';
s.on('readable', function ()
{
var data;
while ((data = this.read()) !== null)
{
msg += data.toString();
}
});
s.on('end', function ()
{
console.log('received', info.topic, msg);
assert.equal(msg, 'hello');
c.end();
});
});
```
Finally, a program which connects to the server and publishes a message to a
topic:
```javascript
// client_publish.js
var MQlobberClient = require('mqlobber').MQlobberClient,
c = require('net').createConnection(parseInt(process.argv[2])),
mq = new MQlobberClient(c);
mq.publish(process.argv[3], function ()
{
c.end();
}).end('hello');
```
Run two servers listening on ports 8600 and 8601:
```shell
node server.js 8600 &
node server.js 8601 &
```
Subscribe to two topics, `foo.bar` and wildcard topic `foo.*`, one against each
server:
```shell
node client_subscribe.js 8600 foo.bar &
node client_subscribe.js 8601 'foo.*' &
```
Then publish a message to the topic `foo.bar`:
```shell
node client_publish.js 8600 foo.bar
```
You should see the following output, one line from each subscriber:
```
received foo.bar hello
received foo.bar hello
```
Only the servers should still be running and you can now terminate them:
```shell
$ jobs
[1]- Running node server.js 8600 &
[2]+ Running node server.js 8601 &
$ kill %1 %2
[1]- Terminated node server.js 8600
[2]+ Terminated node server.js 8601
```
## Installation
```shell
npm install mqlobber
```
## Licence
[MIT](LICENCE)
## Test
```shell
grunt test
```
## Lint
```shell
grunt lint
```
## Code Coverage
```shell
grunt coverage
```
[Istanbul](http://gotwarlost.github.io/istanbul/) results are available [here](http://rawgit.davedoesdev.com/davedoesdev/mqlobber/master/coverage/lcov-report/index.html).
Coveralls page is [here](https://coveralls.io/r/davedoesdev/mqlobber).
# API
*/
"use strict";
var EventEmitter = require('events').EventEmitter,
BPMux = require('bpmux').BPMux,
util = require('util'),
QlobberDedup = require('qlobber').QlobberDedup,
TYPE_SUBSCRIBE = 0,
TYPE_UNSUBSCRIBE = 1,
TYPE_UNSUBSCRIBE_ALL = 2,
TYPE_PUBLISH = 3,
thirty_two_bits = Math.pow(2, 32);
/**
Create a new `MQlobberClient` object for publishing and subscribing to
messages via a server.
@constructor
@param {Duplex} stream Connection to a server. The server should use [`MQlobberServer`](#mqlobberserverfsq-stream-options) on its side of the connection. How the connection is made is up to the caller - it just has to supply a [`Duplex`](https://nodejs.org/dist/latest-v4.x/docs/api/stream.html#stream_class_stream_duplex). For example, [`net.Socket`](https://nodejs.org/dist/latest-v4.x/docs/api/net.html#net_class_net_socket) or [`PrimusDuplex`](https://github.com/davedoesdev/primus-backpressure#primusduplexmsg_stream-options).
@param {Object} [options] Configuration options. This is passed down to [`QlobberDedup`](https://github.com/davedoesdev/qlobber#qlobberdedupoptions) (which matches messages received from the server to handlers) and [`BPMux`](https://github.com/davedoesdev/bpmux#bpmuxcarrier-options) (which multiplexes message streams over the connection to the server). It also supports the following additional property:
- `{Buffer} [handshake_data]` Application-specific handshake data to send to the server. The server-side [`MQlobberServer`](#mqlobberserverfsq-stream-options) object will emit this as a [`handshake`](#mqlobberservereventshandshakehandshake_data-delay_handshake) event to its application.
@throws {Error} If an error occurs before initiating the multiplex with the server.
*/
function MQlobberClient(stream, options)
{
EventEmitter.call(this);
options = options || {};
this._options = options;
this.subs = new Map();
this._matcher = new QlobberDedup(options);
this.mux = new BPMux(stream, options);
this._done = false;
var ths = this;
function error(err)
{
/*jshint validthis: true */
ths.emit('error', err, this);
}
function warning(err)
{
/*jshint validthis: true */
if (!ths.emit('warning', err, this))
{
console.error(err);
}
}
this._warning = warning;
this._unexpected_data = function ()
{
while (true)
{
if (this.read() === null)
{
break;
}
warning.call(this, new Error('unexpected data'));
}
};
this.mux.on('error', error);
function handshake_sent(duplex, complete)
{
if (!complete)
{
ths.emit('backoff');
}
}
this.mux.on('handshake_sent', handshake_sent);
this.mux.on('pre_handshake_sent', handshake_sent);
this.mux.on('drain', function ()
{
ths.emit('drain');
});
this.mux.on('full', function ()
{
ths.emit('full');
});
this.mux.on('removed', function (duplex)
{
ths.emit('removed', duplex);
});
this.mux.on('finish', function ()
{
ths._done = true;
});
this.mux.on('end', function ()
{
ths.subs.clear();
});
var duplex = this.mux.multiplex(options);
function end()
{
/*jshint validthis: true */
error.call(this, new Error('ended before handshaken'));
}
duplex.on('end', end);
duplex.on('error', error);
duplex.on('readable', this._unexpected_data);
this.mux.on('peer_multiplex', function (duplex)
{
duplex.on('error', error);
});
this.mux.on('handshake', function (dplex, hdata, delay)
{
if (dplex === duplex)
{
duplex.removeListener('end', end);
ths.emit('handshake', hdata);
return duplex.end(); // currently no data on initial duplex
}
if (!delay)
{
// duplex was initiated by us (outgoing message)
return;
}
function dend()
{
/*jshint validthis: true */
this.end();
}
// only read from incoming duplex but don't end until all data is read
// in order to allow application to apply back-pressure
dplex.on('end', dend);
dplex.on('error', dend);
if (hdata.length < 1)
{
return warning.call(dplex, new Error('buffer too small'));
}
var info = {},
flags = hdata.readUInt8(0, true),
pos = 1,
topic;
info.single = !!(flags & 1);
info.existing = !!(flags & 4);
if (flags & 2)
{
pos += 8;
if (hdata.length < pos)
{
return warning.call(dplex, new Error('buffer too small'));
}
info.expires = hdata.readUInt32BE(pos - 8, true) * thirty_two_bits +
hdata.readUInt32BE(pos - 4, true);
}
if (flags & 8)
{
pos += 8;
if (hdata.length < pos)
{
return warning.call(dplex, new Error('buffer too small'));
}
info.size = hdata.readUInt32BE(pos - 8, true) * thirty_two_bits +
hdata.readUInt32BE(pos - 4, true);
}
info.topic = hdata.toString('utf8', pos);
var called = false, handshake;
if (info.single)
{
handshake = delay();
}
function done(err)
{
if (called)
{
return;
}
called = true;
if (err)
{
warning.call(dplex, err);
}
if (handshake)
{
var hdata = Buffer.alloc(1);
hdata.writeUInt8(err ? 1 : 0);
handshake(hdata);
}
dplex.end();
}
var handlers = ths._matcher.match(info.topic);
if (handlers.size === 0)
{
return done(new Error('no handlers'));
}
for (var handler of handlers)
{
handler.call(ths, dplex, info, done);
if (info.single)
{
break;
}
}
});
}
util.inherits(MQlobberClient, EventEmitter);
/**
Subscribe to messages published to the server.
@param {String} topic Which messages you're interested in receiving. Message topics are split into words using `.` as the separator. You can use `*` to match exactly one word in a topic or `#` to match zero or more words. For example, `foo.*` would match `foo.bar` whereas `foo.#` would match `foo`, `foo.bar` and `foo.bar.wup`. Note these are the default separator and wildcard characters. They can be changed on the server when [constructing the `QlobberFSQ` object] (https://github.com/davedoesdev/qlobber-fsq#qlobberfsqoptions) passed to [`MQlobberServer`](#mqlobberserverfsq-stream-options).
@param {Function} handler Function to call when a new message is received from the server due to its topic matching against `topic`. `handler` will be passed the following arguments:
- `{Readable} stream` The message content as a [Readable](http://nodejs.org/api/stream.html#stream_class_stream_readable). Note that _all_ subscribers will receive the same stream for each message.
- `{Object} info` Metadata for the message, with the following properties:
- `{String} topic` Topic to which the message was published.
- `{Boolean} single` Whether this message is being given to _at most_ one handler (across all clients connected to all servers).
- `{Integer} expires` When the message expires (number of seconds after 1 January 1970 00:00:00 UTC). This is only present if the server's [`MQlobberServer`](#mqlobberserverfsq-stream-options) instance is configured with `send_expires` set to `true`.
- `{Integer} size` Size of the message in bytes. This is only present if the server's [`MQlobberServer`](#mqlobberserverfsq-stream-options) instance is configured with `send_size` set to `true`.
- `{Function} done` Function to call once you've handled the message. Note that calling this function is only mandatory if `info.single === true`, in order to clean up the message on the server. `done` takes one argument:
- `{Object} err` If an error occurred then pass details of the error, otherwise pass `null` or `undefined`.
@param {Function} [cb] Optional function to call once the subscription has been registered with the server. This will be passed the following argument:
- `{Object} err` If an error occurred then details of the error, otherwise `null`.
@throws {Error} If an error occurs before sending the subscribe request to the server.
*/
MQlobberClient.prototype.subscribe = function (topic, handler, cb)
{
var ths = this, duplex;
function done(err, data)
{
if (!err)
{
var handlers = ths.subs.get(topic);
if (!handlers)
{
handlers = new Set();
ths.subs.set(topic, handlers);
}
handlers.add(handler);
ths._matcher.add(topic, handler);
}
if (cb)
{
var cb2 = cb;
cb = null;
cb2(err, data, duplex);
}
else if (err)
{
ths._warning.call(duplex, err);
}
}
if (this._done)
{
throw new Error('finished');
}
if (this.subs.has(topic))
{
return done();
}
duplex = this.mux.multiplex(Object.assign({}, this._options,
{
handshake_data: Buffer.concat([Buffer.from([TYPE_SUBSCRIBE]),
Buffer.from(topic, 'utf8')])
}));
function end()
{
done(new Error('ended before handshaken'));
}
duplex.on('end', end);
duplex.on('error', done);
duplex.on('readable', this._unexpected_data);
duplex.end();
duplex.on('handshake', function (hdata)
{
this.removeListener('end', end);
if (hdata.length < 1)
{
return done(new Error('buffer too small'));
}
if (hdata.readUInt8(0, true) !== 0)
{
return done(new Error('server error'));
}
done(null, hdata.length > 1 ? hdata.slice(1) : undefined);
});
};
/**
Unsubscribe to messages published to the server.
@param {String} [topic] Which messages you're no longer interested in receiving via the `handler` function. If `topic` is `undefined` then all handlers for all topics are unsubscribed.
@param {Function} [handler] The function you no longer want to be called with messages published to the topic `topic`. This should be a function you've previously passed to [`subscribe`](#mqlobberclientprototypesubscribetopic-handler-cb). If you subscribed `handler` to a different topic then it will still be called for messages which match that topic. If `handler` is `undefined`, all handlers for the topic `topic` are unsubscribed.
@param {Function} [cb] Optional function to call once `handler` has been unsubscribed from `topic` on the server. This will be passed the following argument:
- `{Object} err` If an error occurred then details of the error, otherwise `null`.
@throws {Error} If an error occurs before sending the unsubscribe request to the server.
*/
MQlobberClient.prototype.unsubscribe = function (topic, handler, cb)
{
if (typeof topic === 'function')
{
cb = topic;
topic = undefined;
handler = undefined;
}
var ths = this, done, duplex, hdata;
function done2(err, data)
{
if (cb)
{
var cb2 = cb;
cb = null;
cb2(err, data, duplex);
}
else if (err)
{
ths._warning.call(duplex, err);
}
}
if (this._done)
{
throw new Error('finished');
}
if (topic === undefined)
{
done = function (err, data)
{
if (!err)
{
ths.subs.clear();
ths._matcher.clear();
}
done2(err, data);
};
if (this.subs.size === 0)
{
return done();
}
hdata = Buffer.from([TYPE_UNSUBSCRIBE_ALL]);
}
else
{
done = function (err, data)
{
if (!err)
{
var handlers = ths.subs.get(topic);
if (handlers)
{
if (handler === undefined)
{
handlers.clear();
}
else
{
handlers.delete(handler);
}
if (handlers.size === 0)
{
ths.subs.delete(topic);
}
}
ths._matcher.remove(topic, handler);
}
done2(err, data);
};
var handlers = this.subs.get(topic);
if (!handlers ||
((handler !== undefined) &&
((handlers.size > 1) || !handlers.has(handler))))
{
return done();
}
hdata = Buffer.concat([Buffer.from([TYPE_UNSUBSCRIBE]),
Buffer.from(topic, 'utf8')]);
}
duplex = this.mux.multiplex(Object.assign({}, this._options,
{
handshake_data: hdata
}));
function end()
{
done(new Error('ended before handshaken'));
}
duplex.on('end', end);
duplex.on('error', done);
duplex.on('readable', this._unexpected_data);
duplex.end();
duplex.on('handshake', function (hdata)
{
this.removeListener('end', end);
if (hdata.length < 1)
{
return done(new Error('buffer too small'));
}
if (hdata.readUInt8(0, true) !== 0)
{
return done(new Error('server error'));
}
done(null, hdata.length > 1 ? hdata.slice(1) : undefined);
});
};
/**
Publish a message to the server for interested clients to receive.
@param {String} topic Message topic. The topic should be a series of words separated by `.` (or whatever you configured [`QlobberFSQ`](https://github.com/davedoesdev/qlobber-fsq#qlobberfsqoptions) with on the server).
@param {Object} [options] Optional settings for this publication:
- `{Boolean} single` If `true` then the message will be given to _at most_ one handler (across all clients connected to all servers). If you don't specify this then all interested handlers (across all clients) will receive it.
- `{Integer} ttl` Time-to-live (in seconds) for this message. If you don't specify this then the default is taken from the [`QlobberFSQ`](https://github.com/davedoesdev/qlobber-fsq#qlobberfsqoptions) instance on the server. In any case, `QlobberFSQ`'s configured time-to-live is used to constrain `ttl`'s maximum value.
@param {Function} [cb] Optional function to call once the server has published the message. This will be passed the following argument:
- `{Object} err` If an error occurred then details of the error, otherwise `null`.
@return {Writable} Stream to which to [write](https://nodejs.org/dist/latest-v4.x/docs/api/stream.html#stream_writable_write_chunk_encoding_callback) the message's data. Make sure you [`end`](https://nodejs.org/dist/latest-v4.x/docs/api/stream.html#stream_writable_end_chunk_encoding_callback) it when you're done.
@throws {Error} If an error occurs before sending the publish request to the server.
*/
MQlobberClient.prototype.publish = function (topic, options, cb)
{
if (typeof options === 'function')
{
cb = options;
options = undefined;
}
options = options || {};
var ths = this, duplex, hdata;
function done(err, data)
{
if (cb)
{
var cb2 = cb;
cb = null;
cb2(err, data, duplex);
}
else if (err)
{
ths._warning.call(duplex, err);
}
}
if (this._done)
{
throw new Error('finished');
}
hdata = [Buffer.alloc(2)];
hdata[0].writeUInt8(TYPE_PUBLISH, 0);
hdata[0].writeUInt8((options.single ? 1 : 0) |
((options.ttl ? 1 : 0) << 1),
1);
if (options.ttl)
{
hdata.push(Buffer.alloc(4));
hdata[1].writeUInt32BE(options.ttl, 0, true);
}
hdata.push(Buffer.from(topic, 'utf8'));
duplex = this.mux.multiplex(Object.assign({}, this._options,
{
handshake_data: Buffer.concat(hdata)
}));
function end()
{
done(new Error('ended before handshaken'));
}
duplex.on('end', end);
duplex.on('error', done);
duplex.on('readable', this._unexpected_data);
duplex.on('handshake', function (hdata)
{
this.removeListener('end', end);
if (hdata.length < 1)
{
return done(new Error('buffer too small'));
}
if (hdata.readUInt8(0, true) !== 0)
{
return done(new Error('server error'));
}
done(null, hdata.length > 1 ? hdata.slice(1) : undefined);
});
return duplex;
};
exports.MQlobberClient = MQlobberClient;
|