TimMoore / lagom-sbt-standalone

lagom-sbt-standalone

A basic example of building a Lagom project to run outside of the Lightbend Production Suite (aka ConductR).

This was initially created from the lagom-java template (sbt new lagom/lagom-java.g8), with the following changes:

• Added ConfigurationServiceLocator to Guice modules in each implementation project, as described in the Lagom documentation
• Added static port bindings to each service (hello-impl: 8001, hello-stream-impl: 8002)
• Added a static service location to hello-impl for cas_native (the Cassandra server)
• Added a static service location to hello-stream-impl for hello

To test this:

1. Open a terminal and clone the repository to your workstation (git clone https://github.com/TimMoore/lagom-sbt-standalone.git)
2. cd lagom-sbt-standalone
3. sbt to enter the sbt console
4. dist (from the sbt prompt) to create distribution packages
5. lagomCassandraStart (from the sbt prompt) to run a Cassandra server on port 4000
6. Leave sbt running in that terminal window and open two more terminals in the same directory
7. In one terminal:
   1. cd hello-impl/target/universal
   2. unzip hello-impl-1.0-SNAPSHOT.zip (or, if you don't have the unzip command, use any tool to unzip the file into the same directory)
   3. cd hello-impl-1.0-SNAPSHOT
   4. bash bin/hello-impl -Dlagom.cluster.join-self=on (or bin/hello-impl.bat -Dlagom.cluster.join-self=on on Windows)
8. In the other terminal:
   1. cd hello-stream-impl/target/universal
   2. unzip hello-stream-impl-1.0-SNAPSHOT.zip
   3. cd hello-stream-impl-1.0-SNAPSHOT
   4. bash bin/hello-stream-impl -Dlagom.cluster.join-self=on (or bin/hello-stream-impl.bat -Dlagom.cluster.join-self=on on Windows)

This runs each of the services on the configured port, as single-node clusters.

You can press control-C to exit the services, and run lagomCassandraStop in the initial sbt console to stop Cassandra (or simply exit sbt).

Steps for lagom-scala project

For those looking for a basic example of building a Lagom project, in Scala, to run outside of the Lightbend Production Suite (aka ConductR) follow this link - lagom-scala-sbt-standalone.

Caveats

This configuration is not suitable for production deployments, it's just intended as a starting point. Here are some of the limitations to be aware of.

• Static service locator configuration is difficult to manage in practice, as it requires configuration to be duplicated across all services, and configuring additional services requires a restart.
• The provided ConfigurationServiceLocator only supports a single endpoint per service, which reduces resilience and elasticity.
• Using -Dlagom.cluster.join-self=on restricts each service to run on a single node. Creating a multi-node cluster requires configuring seed nodes as described in the Lagom Cluster documentation
• The provided launcher scripts do not attempt to handle process supervision or health monitoring

Lightbend Production Suite (ConductR) provides easy-to-use solutions to these problems and others.