Is it possible to use a Subject in ZeroMQ? - zeromq

Question

I have a little project that implements NATS Queueing
This is the code:
import * as NATS from '../node_modules/nats' // for typescript
var nats = require('nats');
var config = require('./config');
var opt: NATS.ClientOpts = {'noRandomize': false, 'reconnect': true,
'maxReconnectAttempts': -1, 'servers':config.nat.servers, 'user':
config.nat.user , 'pass': config.nat.pass };
var nc: NATS.Client = nats.connect(opt);
nc.on('error', function(e) {
console.error('Error nats: ' + e);
});
nc.on('close', function() {
console.error('CLOSED nats');
});
nc.subscribe('serviceA', { 'queue': 'A' }, function (request, replyTo) {
console.debug('I exec serviceA via nats:');
j = JSON.parse(request);
console.debug(j);
let ok = {"res": "i am response for service A"}
nc.publish(replyTo, JSON.stringify(ok));
}
let cmd = '{"a": 5, "b": "i am sample"}';
nc.requestOne('serviceA', cmd, {}, 15000, function (response) {
if (response.code && response.code === nats.REQ_TIMEOUT) {
console.error('server timeout');
console.error(response.code);
} else {
console.log('A see this response: ' + response);
}
});
nc.subscribe('serviceB', { 'queue': 'B' }, function (request, replyTo) {
console.debug('I exec serviceB via nats:');
j = JSON.parse(request);
console.debug(j);
let ok = {"res": "i am response for service B"}
nc.publish(replyTo, JSON.stringify(ok));
}
let cmd = '{"c": 5, "d": "i am sample"}';
nc.requestOne('serviceB', cmd, {}, 15000, function (response) {
if (response.code && response.code === nats.REQ_TIMEOUT) {
console.error('server timeout');
console.error(response.code);
} else {
console.log('B see this response: ' + response);
}
});
As you can see, there are 2 services - serviceA on queue A and serviceB on queue B and 2 clients: the first calls service A and the second calls service B
NATS implements Subject ( 'serviceA' and 'serviceB' )
Now, I want try to convert the example using ØMQ I found a similar sample using ZeroMQ
But I can find nothing sample on Subject.
Perhaps ØMQ uses ROUTER so as to implements a subject
Can you help me to implement subject into a ZeroMQ example?

Answer 1

Q: Is it possible to use a Subject in ZeroMQ?A: Yes, it is:
The long story short - one does not need any zmq.ROUTER for doing this, just use a PUB / SUB formal pattern.
Beware: ZeroMQ Socket()-instance is not a tcp-socket-as-you-know-it.
Best
read about the main conceptual differences in [ ZeroMQ hierarchy in less than a five seconds ] Section.
The Publisher side:
import zmq
aCtx = zmq.Context()
aPub = aCtx.Socket( zmq.PUB )
aPub.bind( "tcp://123.456.789.012:3456" )
aPub.setsockopt( zmq.LINGER, 0 )
aPub.setsockopt( zmq.<whatever needed to fine-tune the instance>, <val> )
i = 0
while true:
try:
aPub.send( "ServiceA::[#{0:_>12d}] a Hello World Message.".format( i ) )
aPub.send( "ServiceABCDEFGHIJKLMNOPQRSTUVWXYZ........" )
aPub.send( "ServiceB::[#{0:_>12d}] another message...".format( i / 2 ) ) if ( i == ( 2 * ( i / 2 ) ) ) else pass
sleep( 1 ); i += 1
except KeyboardInterrupt:
print( "---< will exit >---" )
break
print( "---< will terminate ZeroMQ resources >---" )
aPub.close()
aCtx.term()
The Subscriber side:
import zmq
aCtx = zmq.Context()
aSub = aCtx.Socket( zmq.SUB )
aSub.connect( "tcp://123.456.789.012:3456" )
aSub.setsockopt( zmq.LINGER, 0 )
aSub.setsockopt( zmq.SUBSCRIBE, "ServiceA" ) # Subject ( 'serviceA' and 'serviceB' )
aSub.setsockopt( zmq.SUBSCRIBE, "ServiceB" ) # Kindly see the comments below
# # Kindly see API on subscription management details
#
# # Yet another "dimension"
# # to join ingress
# # from multiple sources
#Sub.connect( "<transport-class>://<addr>:<port>" )
# <transport-class :: { inproc | ipc | tcp | pgm | epgm | vmci }
# .connect()-s the same local SUB-AccessPoint to another PUB-side-AccessPoint
# to allow the PUB/SUB Scalable Formal Communication Archetype Pattern
# join a message flow from different source PUB-sides
#Sub.setsockopt( zmq.SUBSCRIBE, "ServiceZ" )
while true:
try:
print( "<<< (((_{0:s}_)))".format( aSub.recv() ) )
except KeyboardInterrupt:
print( "---< will exit >---" )
break
print( "---< will terminate ZeroMQ resources >---" )
aSub.close()
aCtx.term()