This application demos the use of spring integration with a jdbc datasource for leader election and lock acquisition
In com.example.leaderelection.IntegrationConfiguration everything is configured.
In com.example.leaderelection.LeaderShipInfo the leadership changes are consumed and exposed as bean.
There are two ways of scheduling jobs in all application with the same schedule, but ensuring only one node will execute.
See com.example.leaderelection.ScheduledTaskOnLeader for execution only on the leader.
See com.example.leaderelection.ScheduledTaskWithLock for execution only if a lock could be acquired.
docker compose up -d
Just run the spring boot app and override the binding port by configuring the env var SERVER_PORT to the desired port.
SERVER_PORT=8091 ./mvnw spring-boot:run
A org.springframework.integration.jdbc.lock.DefaultLockRepository is used which provides support to acquire locks, which will expire after 10 seconds if not renewed.
For selecting a leader the org.springframework.integration.support.leader.LockRegistryLeaderInitiator is used. This will try to re-acquire a lock on each node (in this example every 5 seconds).
If a node is not the leader it will try to (intially) acquire a lock every 1 second.
If a node dies unexpected and cannot return the lock, it will expire after 10 seconds and another node will acquire the lock 1 second later.
So the system is leaderless a maximum of 11 seconds, if the leader dies immediately after re-aquiring its lock.