Deploy Lagom Framework as standalone jar/docker

Question

Is it possible to deploy a Lagom Application as a standalone running jar or Docker Container? And if yes, how?

Answer 1

Yes, it is possible to deploy a Lagom application as a standalone JAR/Docker container. In order to do this, you can follow these steps.

1. Configure Cassandra Contact Points: If you are planning to use dynamic service location for your service but need to statically locate Cassandra, which is obvious in Production, then modify the application.conf of your service. Also, disable Lagom's ConfigSessionProvider and fall back to the one provided in akka-persistence-cassandra, which uses the list of endpoints listed in contact-points. Your Cassandra configuration should look something like this-

cassandra.default {
## list the contact points here
contact-points = ["127.0.0.1"]
## override Lagom’s ServiceLocator-based ConfigSessionProvider
session-provider = akka.persistence.cassandra.ConfigSessionProvider
}
cassandra-journal {
contact-points = ${cassandra.default.contact-points}
session-provider = ${cassandra.default.session-provider}
}
cassandra-snapshot-store {
contact-points = ${cassandra.default.contact-points}
session-provider = ${cassandra.default.session-provider}
}
lagom.persistence.read-side.cassandra {
contact-points = ${cassandra.default.contact-points}
session-provider = ${cassandra.default.session-provider}
}

2. Provide Kafka Broker Settings (If you are using Kafka Message Broker): Next step is to provide Kafka broker settings if you plan to use Lagom's streaming service. For this, you need to modify the application.conf of your service, if Kafka service is to be statically located, which is the case when your service acts only like a consumer, otherwise, you do not need to give following configurations.

lagom.broker.kafka {
  service-name = ""
  brokers = "127.0.0.1:9092"
  client {
    default {
      failure-exponential-backoff {
        min = 3s
        max = 30s
        random-factor = 0.2
      }
    }
    producer = ${lagom.broker.kafka.client.default}
    producer.role = ""
    consumer {
      failure-exponential-backoff = ${lagom.broker.kafka.client.default.failure-exponential-backoff}
      offset-buffer = 100
      batching-size = 20
      batching-interval = 5 seconds
    }
  }
}

3. Create Akka Cluster: At last, we need to create an Akka cluster on our own. Since we are not using ConductR, we need to implement the joining yourself. This can be done by adding the following lines in application.conf.

akka.cluster.seed-nodes = [
  "akka.tcp://MyService@host1:2552",
  "akka.tcp://MyService@host2:2552"]

Now, we know what configurations we need to provide to our service, let's take a look at the steps of deployment. Since we are using just java -cp command, we need to package our service and run it. To simplify the process, we have created a shell script for it.

For a complete example, you can refer to our GitHub repo - Lagom Scala SBT Standalone project.

I hope it helps!