1 request exchange, 1 reply exchange, N number responses - rabbitmq

Question

I want to push out 1 response and wait X milliseconds for N responses based on a correlation ID in the headers.
Current code is pretty simple: Send a call then start polling indiscriminately. That works ... for one call.
I know there is talk of a JMS solution ("JMSReader?") that spawns N number of listeners looking for correlation ID allowing these futures to time out, but I am not finding anything remotely related.

Answer 1

Here is a demo app that shows one way to do it...
#SpringBootApplication
public class So57377491Application {
public static void main(String[] args) {
SpringApplication.run(So57377491Application.class, args);
}
private final ConcurrentMap<String, List<String>> pending = new ConcurrentHashMap<>();
private final ConcurrentMap<String, SettableListenableFuture<List<String>>> futures = new ConcurrentHashMap<>();
#Bean
public ApplicationRunner runner(RabbitTemplate template) {
return args -> {
this.pending.put("bar", new ArrayList<>());
this.futures.put("bar", new SettableListenableFuture<>());
template.convertAndSend("so57377491", "", "Foo", msg -> {
msg.getMessageProperties().setCorrelationId("bar");
msg.getMessageProperties().setReplyTo("replyExchange/so57377491-replies");
return msg;
});
try {
List<String> list = this.futures.get("bar").get(5, TimeUnit.SECONDS);
System.out.println(list);
}
catch (TimeoutException toe) {
System.out.println("Partial result after timeout " + this.pending.remove("bar"));
}
finally {
this.futures.remove("bar");
}
};
}
#RabbitListener(bindings = #QueueBinding(
value = #Queue(value = "so57377491-1"),
exchange = #Exchange(value = "so57377491", type = "fanout")))
public String listen1(String in) {
System.out.println(in);
return in.toUpperCase();
}
#RabbitListener(bindings = #QueueBinding(
value = #Queue(value = "so57377491-2"),
exchange = #Exchange(value = "so57377491", type = "fanout")))
public String listen2(String in) {
System.out.println(in);
return in.toLowerCase();
}
#RabbitListener(bindings = #QueueBinding(
value = #Queue(value = "so57377491-3"),
exchange = #Exchange(value = "so57377491", type = "fanout")))
public String listen3(String in) {
System.out.println(in);
return in + in;
}
#RabbitListener(bindings = #QueueBinding(
value = #Queue(value = "so57377491-replies"),
exchange = #Exchange(value = "replyExchange", type = "fanout")))
public void replies(String in, #Header(AmqpHeaders.CORRELATION_ID) String correlationId) {
System.out.println(in);
List<String> list = this.pending.get(correlationId);
if (list == null) {
System.out.println("Late reply for " + correlationId);
}
else {
list.add(in);
if (list.size() == 3) {
this.futures.get(correlationId).set(list);
this.pending.remove(correlationId);
}
}
}
}
Result
Foo
Foo
Foo
foo
FOO
FooFoo
[foo, FOO, FooFoo]