§Production

Lagom doesn’t prescribe any particular production environment. If you are interested in deploying on Kubernetes, see our guide that demonstrates how to deploy the Chirper example application.

§Deployment considerations

The deployment platform determines the type of archive you will need to use for packaging your microservices and the way you provide service location, including that for Cassandra:

• Lagom leverages the sbt-native-packager to produce archives of various types. By default, sbt produces zip archives, but you can easily produce tar.gz, MSI, debian, RPM, Docker and more.

• At runtime, services need to locate each other. This requires you to provide an implementation of a ServiceLocator. And, the deployment platform you choose might impose its own requirements on configuration.

• The Cassandra module provided by akka-persistence-cassandra uses static lookup by default. Lagom overrides that behavior by implementing a Session provider based on service location. That allows all services to continue to operate without the need to redeploy if/when the Cassandra contact-points are updated or fail. Using this approach provides higher resiliency. However, it is possible to hardcode the list of contact-points where Cassandra may be located even when the server is stared with a dynamic service locator as described in the section below.

§Deploying using static Cassandra contact-points

If you want to use dynamic service location for your services but need to statically locate Cassandra, modify the application.conf for your service. You will need to 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. The application.conf settings will be applied in all environments (development and production) unless overridden. See developer mode settings on overriding Cassandra setup in Dev Mode for more information on settings up Cassandra in dev mode.

To set up static Cassandra contact-points and disable ConfigSessionProvider, modify the following sections of the application-conf file:

cassandra.default {
  ## list the contact points  here
  contact-points = ["10.0.1.71", "23.51.143.11"]
  ## 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}
}

§Using static values for services and Cassandra to simulate a managed runtime

While we would never advise using static service locations in production, to simulate a working Lagom system in the absence of a managed runtime, you can deploy Lagom systems to static locations by using static configuration. When using static service location, you can also hardcode Cassandra locations. To achieve this, follow these steps:

1. Specify service locations in application.conf.
   The ConfigurationServiceLocator reads service locator configuration out of Lagom’s application.conf file. This example specifies static locations for two Lagom services:

   lagom.services {
     serviceA = "http://10.1.2.3:8080"
     serviceB = "http://10.1.2.4:8080"
   }
   

2. In production mode, add the ConfigurationServiceLocatorComponents trait in your application, as shown in the following example. Use the LagomDevModeComponents trait in a development environment.

   import com.lightbend.lagom.scaladsl.devmode.LagomDevModeComponents
   import com.lightbend.lagom.scaladsl.server._
   import com.lightbend.lagom.scaladsl.client.ConfigurationServiceLocatorComponents
   
   class HelloApplicationLoader extends LagomApplicationLoader {
   
     override def load(context: LagomApplicationContext) =
       new HelloApplication(context) with ConfigurationServiceLocatorComponents
   
     override def loadDevMode(context: LagomApplicationContext) =
       new HelloApplication(context) with LagomDevModeComponents
   
   }

3. Optionally, to hard code Cassandra locations, add them in application.confas values for cas_native, as illustrated below:

   lagom.services {
     cas_native = "tcp://10.1.2.3:9042"
   }