Publisher and subscriber not working in negative scenarios - node.js

Question

Hi I am using zeroMQ for my node application where i use the publisher and subscriber for message queuing.Below is my code
Publisher.js
var zmq = require('zmq')
var publisher = zmq.socket('pub')
publisher.bind('tcp://127.0.0.1:7000', function(err) {
if(err)
console.log(err)
else
console.log("Listening on 7000...")
})
setTimeout(function() {
console.log('sent');
publisher.send("hi")
}, 1000)
process.on('SIGINT', function() {
publisher.close()
console.log('\nClosed')
})
Subscriber.js
var zmq = require('zmq')
var subscriber = zmq.socket('sub')
subscriber.on("message", function(reply) {
console.log('Received message: ', reply.toString());
})
subscriber.connect("tcp://localhost:7000")
subscriber.subscribe("")
process.on('SIGINT', function() {
subscriber.close()
console.log('\nClosed')
})
The above code is working fine if both the publisher and subscriber are running.If i stop my subscriber i'm not able to receive the publisher's data when the subscriber is offline.I want to persist the data even if my subscriber is down.I'm stuck here.Any help will be much appreciated.

Answer 1

See the 'Last value caching' pattern on zmq docs site. You can extend the example with the client first subscribing to a pattern with the latest item it had received, and the lvc proxy to resend the missing values(it has to cache them first). But this might work for a small number of cached items where disconnects happen rarely, otherwise PUSH might be the better option. PUB-SUB is not intended to support buffering.