How to create/customize Spring Boot Actuators for exposing application healthchecks and diagnostics for my Camunda Application?

Assuming that you are using the camunda spring boot starter: Two default health indicators for ProcessEngine and JobExecutor are included with the starter, have a look at:

https://github.com/camunda/camunda-bpm-spring-boot-starter/tree/master/starter/src/main/java/org/camunda/bpm/spring/boot/starter/actuator

 @Override
  protected void doHealthCheck(Builder builder) throws Exception {
    boolean active = jobExecutor.isActive();
    if (active) {
      builder = builder.up();
    } else {
      builder = builder.down();
    }
    builder.withDetail("jobExecutor", Details.from(jobExecutor));
  }

which should give you an idea how to implement springs AbstractHealthIndicator, access camunda components and use them for health checks.

I have been able to customize the existing healthcheck actuator. Sharing the code below for people who want to customize in there projects.

@Component
public class X extends AbstractHealthIndicator {
    @Autowired
    public JobExecutor jobExecutor;

    @Override
    protected void doHealthCheck(Builder builder) throws Exception {
        boolean active = jobExecutor.isActive();
        if (active) {
            builder = builder.up();
        } else {
            builder = builder.down();
        }
        builder.withDetail("jobExecutor", healthDetails(jobExecutor));
    }

    private Details healthDetails(JobExecutor jobExecutor) {
        final DetailsBuilder builder = Details.builder().name(jobExecutor.getName())
                .lockOwner(jobExecutor.getLockOwner()).lockTimeInMillis(jobExecutor.getLockTimeInMillis())
                .maxJobsPerAcquisition(jobExecutor.getMaxJobsPerAcquisition())
                .waitTimeInMillis(jobExecutor.getWaitTimeInMillis());

        for (ProcessEngineImpl processEngineImpl : jobExecutor.getProcessEngines()) {
            builder.processEngineName(processEngineImpl.getName());
        }

        return builder.build();
    }

}