akka-discovery-service-locator eagerly uses DNS-SRV Lookups

akka-discovery-service-locator is a ServiceLocator implementation that produces Akka Discovery Lookup() queries which are then resolved by the underlying AkkaDiscovery instance.

The Lagom bridge from ServiceLocator takes a single String as an input and eagerly uses default portName and protocol values to produce Lookup(name, portName, protocol) queries. When Akka Discovery is setup to use akka-dns that Lookup query is turned into a DNS SRV request.

The issue is Lagom users are no longer able to generate DNS A requests since the combination of akka-discovery-service-locator and akka-dns only creates DNS SRV queries.

This is an issue when a Lagom client wants to consume a service that provides server-side load balancing and only expose DNS A registries.

---

The current workaround is to tune AkkaDiscovery to use an aggregate implementation and hardcode the response to a Lookup query for an external service:

akka {
  discovery {
    method = aggregate
    aggregate {
      discovery-methods = ["config", "akka-dns"]
    }
    config {
      services {
		## same value than below. Will shortcircuit the lookup 
		## and avoid query failure on the DNS
        external-service {
          endpoints = [
            {
              host = "api.external.io"
              port = 443
            }
          ]
        }
      }
    }
  }
}

lagom.akka.discovery {
  defaults {...}
  service-name-mappings {
    ## same value than above
    external-service { 
        ## no need to use the `lookup` setting
        scheme = https
    }
  }
}

[octonato]

@ralphlaude, next time. You can just pick an issue and leave a note saying you are working on it.

We lost your message in the see of GitHub notifications we get daily.

[octonato]

@ralphlaude, my excuses. I see you asked if you could pick this one to work. In fact, this is fixed by #2603. Once it’s merged, I don’t think there is any work left.