RediBox core PUBSUB is more than just the standard redis clients single 'message' event handler. It's setup to allow subscribing just like you would with a node event emitter.
Internally though, RediBox has a on 'message' handler that routes pubsub messages to an event emitter which you're listening to when you subscribe, this gives you better control over channel flow.
Subscribe once to single or multiple redis channels, i.e the same as node's EventEmitter.once(). On receiving the first event per channel the client will automatically unsub (if no other subscribers) and remove the listener from the emitter. Optionally you can also specify a timeout, e.g. I want one event from this channel within 5000 ms, else let me know it timed out.
This accepts a single channel as a string or multiple channels as an Array.
Parameters:
- channels:
String || Array, A string or array of strings of channels to subscribe to. - listener:
Function, Your event listener. - timeout:
Number, Optional timeout ms - timeout after specified length of time, listener is called with a timeout event (event.timeout). - RETURNS:
Promise
Example:
RediBox.subscribeOnce([
'requestID-123456:request:dataPart1',
'requestID-123456:request:dataPart2',
'requestID-123456:request:dataPart3'
], function (message) { // on message received listener
if (message.timeout) {
return console.error(new Error(`Sub once to channel ${message.channel} timed out! =( `));
}
console.log('I received a message \\o/:');
console.dir(message.channel); // channel name
console.dir(message.timestamp); // when the message was received
console.dir(message.data); // JSON parsed data
} , 3000).then(() => {
console.log('Subscribed once to multiple channels!');
// test publish to just one channel, the rest will timeout
// this is normally sent from somewhere else
RediBox.publish('requestID-123456:request:dataPart1', {
someArray: [1, 2, 3, 4, 5],
somethingElse: 'foobar'
});
});
/**
CONSOLE OUTPUT:
Subscribed once to multiple channels!
I received a message \o/:
'requestID-123456:request:dataPart1'
1453677089
{ someArray: [ 1, 2, 3, 4, 5 ], somethingElse: 'foobar' }
[Error: Sub once to channel requestID-123456:request:dataPart2 timed out! =( ]
[Error: Sub once to channel requestID-123456:request:dataPart3 timed out! =( ]
*/Subscribe to all of the channels provided but as soon as the first message is received from any channel then unsubscribe from all the provided channels.
This accepts a single channel as a string or multiple channels as an Array.
Parameters:
- channels:
String || Array, A string or array of strings of channels to subscribe to. - listener:
Function, Your event listener. - timeout:
Number, Optional timeout ms - timeout after specified length of time, listener is called with a timeout event (event.timeout). - RETURNS:
Promise
Example:
RediBox.subscribeOnceOf([
'requestID-123456:request:success',
'requestID-123456:request:error', // not sure why you'd do this, but you get the idea
], function (message) { // on message received listener
if (message.timeout) {
return console.error(new Error(`Sub once of channel ${message.channel} timed out! =( `));
}
console.log('I received a message \\o/:');
// insert success kid meme
console.dir(message.channel); // channel name
console.dir(message.timestamp); // when the message was received
console.dir(message.data); // JSON parsed data
}, 3000).then(() => {
// test publish to just one channel, the rest will unsub after receiving this
RediBox.publish('requestID-123456:request:success', {
someArray: [1, 2, 3, 4, 5],
somethingElse: 'foobar'
});
}); // I want an event back within 3 seconds for any channel before they all timeout
/**
CONSOLE OUTPUT:
Subscribed once of multiple channels!
I received a message \o/:
'requestID-123456:request:success'
1453677089
{ someArray: [ 1, 2, 3, 4, 5 ], somethingElse: 'foobar' }
*/Equivalent to node's EventEmitter.on() with an optional subscribedCallback to let you know when subscribed. This accepts a single channel as a string or multiple channels as an Array.
Parameters:
- channels:
String || Array, A string or array of strings of channels to subscribe to. - listener:
Function, Your event listener. - RETURNS:
Promise
Example:
RediBox.subscribe('getMeSomeDataMrWorkerServer', function (message) { // your listener
console.log('I received a message \\o/:');
console.dir(message.channel); // channel name
console.dir(message.timestamp); // when the message wa received
console.dir(message.data); // JSON parsed data
}).then(() => {
// test publish to this channel
// this is normally sent from somewhere else
RediBox.publish('getMeSomeDataMrWorkerServer', {
someData: [1, 2, 3, 4, 5],
worker: 'serverXYZ'
});
});
/**
CONSOLE OUTPUT:
I received a message \o/:
'getMeSomeDataMrWorkerServer'
1453678851
{ someData: [ 1, 2, 3, 4, 5 ], worker: 'serverXYZ' }
*/Unsubscribe from single or multiple channels. Note that even though listener is optional, you should pass the original listener function that you provided when you subscribed to those channels - if available (see example below).
Parameters:
- channels:
String || Array, A string or array of strings of channels to unsubscribe from. - listener:
Function, Optional event listener. - RETURNS:
Promise- But can just be used without the promise - fire and forget
Example:
// your on message received listener
const myListener = function (message) {
console.log(message.data); // HELLO but not GOODBYE gets logged
};
RediBox.subscribe('getMeSomeDataMrWorkerServer', myListener).then(() => {
RediBox.publish('getMeSomeDataMrWorkerServer', 'HELLO');
// some time later on:
setTimeout(function () {
RediBox.unsubscribe('getMeSomeDataMrWorkerServer', myListener);
RediBox.publish('getMeSomeDataMrWorkerServer', 'GOODBYE');
}, 2000);
});
/**
CONSOLE OUTPUT:
HELLO
*/Publishes a message to single or multiple channels. Non string values automatically get JSON stringified.
Parameters:
- channels:
String || Array, A string or array of strings of channels to publish to. - message:
String || Object, Optional event listener. - RETURNS:
Promise- But can just be used without the promise - fire and forget
Example:
RediBox.publish('someChannel', 'HELLO');
// or with objects:
RediBox.publish(['someChannel', 'someOtherChannel'], {
foo: 'bar'
});