How do I start rabbitmq-native consumers configured in application.yml? - grails

Question

I have a Grails 3.1.12 app with the rabbitmq-native 3.3.1 plugin.
In build.gradle:
compile "org.grails.plugins:rabbitmq-native:3.3.1"
This app runs in a cluster and I want the instances to act as workers. A message written to the exchange should go to one instance, the next message to another instance, and so on.
I can bind consumers to queues using a static block in each consumer:
static rabbitConfig = [
"queue": "my.queue.that.is.bound.to.some.exchange"
]
Or I can bind them in application.yml:
rabbitmq:
exchanges:
- name: some.exchange
type: fanout
queues:
- name: my.queue.that.is.bound.to.some.exchange
exchange: some.exchange
consumers:
MyConsumer:
queue: my.queue.that.is.bound.to.some.exchange
But when I map consumers to queues in application.yml, the consumer is not consuming messages on the queue. I managed to dump the RabbitMQ status report, which shows the consumer is stopped:
[
{
"consumers":
[
{
"fullName": "MyConsumer",
"load": 0.0,
"name": "MyConsumer",
"numConfigured": 1,
"numConsuming": 1,
"numProcessing": 0,
"queue": "my.queue.that.is.bound.to.some.exchange",
"runningState": {
"enumType": "com.budjb.rabbitmq.RunningState",
"name": "STOPPED"
}
}
],
"host": "localhost",
"name": "35d07d1d-9cdc-460f-a63d-da24eb72b479",
"port": 5672,
"runningState": {
"enumType": "com.budjb.rabbitmq.RunningState",
"name": "RUNNING"
},
"virtualHost": "/"
}
]
I tried calling rabbitContext.startConsumers() or even consumerManager.start() from Bootstrap.init(), but the consumers are not populated yet (consumerManager.consumers == []), so it does nothing.
I'm trying to keep the consumer bindings in an externalized configuration, so I'd can selectively turn consumers on or off depending on context. I might turn off heavy consumers on nodes that serve web traffic, for example. It would be more awkward to do in a static initializer block in the consumer, as opposed to a configuration file.
So, how do I start my consumers when their queue binding is defined in application.yml?

Answer 1

I did some debugging on the plugin, and found out that when it starts the consumers it validates the configuration with this method:
#Override
boolean isValid() {
boolean valid = true
if (!queue && !exchange) {
log.warn("consumer is not valid because it has no queue nor exchange defined")
valid = false
}
if (queue && exchange) {
log.warn("consumer is not valid because is has both a queue and an exchange defined")
valid = false
}
if (binding instanceof Map && !(match in ["any", "all"])) {
log.warn("match must be either 'any' or 'all'")
valid = false
}
return valid
}
In my case, the validation was failing because my configuration didn't have the binding and match properties, which shouldn't be required for queue consumers.
Adding them with bogus values made the configuration validate and the consumers start properly and consume messages.
Not sure if this would help your case as well, but in mine it did :)