clock

A sample app for publishing temporal events

the service uses spring-cloud-stream to connect to RabbitMQ. the current configuration will create an exchange named temporalEvents and publish a message using the routing key of the same value (ie temporalEvents). the service also uses spring-integration, along with Hazelcast, to support leader election so that cluster of services can be started but only one will have responsibility publishing events. all of the nodes will create a connection to RabbitMQ but only one will publish the actual message.

running locally

the existing configuration assumes that you have an instance of RabbitMQ running locally and using the default port of 5672. if you're using Docker

docker run -d --hostname local-rmq --name local-rmq -p 5672:5672 -p 15672:15672 rabbitmq:management

running a single instance of the service is as easy as mvn spring-boot:run -Drun.profiles=local. this will start a single node cluster and connect to RabbitMQ as you would expect.

if, however, you'd like to start a multi-node cluster while still running locally, do the following:

1. mvn clean package will create a jar in the target folder
2. start the first node with java -Dspring.profiles.active=local -jar target/clock-0.1.0.jar
3. open another terminal window and start the second instance with the same command but change the service port to something other than 8080. for example: java -Dspring.profiles.active=local -Dserver.port=8081 -jar target/clock-0.1.0.jar

you should see log information from Hazelcast that indicates a named cloudCluster has been created and it contains two members. the first instance that you started should be the leader and the one that is publishing the events. If you kill that instance, leadership should transfer to the remaining node and message publishing continues.

running in the cloud - cloud foundry

I have also included a configuration profile, cloud, and a manifest file for publishing the service to cloud foundry. Both the configuration and manifest file assume that the target space contains an instance of the CloudAMQP service (ie. RabbitMQ) named 'rabbitmq'.