Summary

A Spring boot Application with Leader Election using spring-integration.

Features

• Leader Election using Zookeeper and Spring-integration

• Loads resource(s) that are decorated with build time properties such as project.version.

  See docs

• Use @Primary, when there are more than 1 candidate beans found for autowiring
• DropWizard ScheduledReporters have start and stop methods, but are not designed to be started and stopped more thanonce. Hence using a Prototype Scope with these Reporters to get a different instance on Leader election.
• System Metrics and Health using spring-actuator

• Uses an external XML configuration file in addition to application.properties

  • Uses apache commons configuration to parse the XML configuration
  • Issue: PlaceHolders in Lists are not expanded

Notes

1. Structured app as shown here
2. Spring-Integration documentation on leader election
3. Spring-cloud: _<> has been sunset in favor of Spring-Integration.
4. Interesting issue
5. Source on github
6. Roles

Testing

ZooKeeper

If you don't have Zookeeper installed, the easiest way to run Zookeeper is to start TestingServer. See com.tutorial.spring.pictogram.PictogramApplicationTests

Leader Election

Use SSH local port forwarding:

ssh -NL 9191:localhost:2181 localhost

Starting Multiple Instances of Pictogram

Change the following Program Arguments for each instance:

--zookeeper.port=9191
--management.port=9091
--server.port=9090