How to implement custom actuator endpoint to check zookeeper health? - apache-zookeeper

Question

I would like to implement a custom endpoint class to check Zookeeper health:
http://localhost:8080/actuator/health/zookeeper
PROBLEM: Do I extend AbstractHealthIndicaitor or implement HealthIndicator class?
HealthIndicator class
public class CustomHealth implements HealthIndicator {
#Override
public Health health() {
int errorCode = check(); // perform some specific health check
if (errorCode != 0) {
return Health.down()
.withDetail("Error Code", errorCode).build();
}
return Health.up().build();
}
public int check() {
// Our logic to check zookeeper health
return 0;
}
}
AbstractHealthIndicator class
public class CustomHealth extends AbstractHealthIndicator {
#Override
protected void doHealthCheck(Health.Builder builder) throws Exception
{
// Our logic to check zookeeper health
}
}
I'm confused on which approach to use. I believe the logic to check zookeeper health is to simply declare an CuratorFramework object then do curator.getState() and return builder from there and for endpoint, attach #RestControllerEndPoint to declare the path. Please help!

Answer 1

It is up to you which one to choose, the difference is that AbstractHealthIndicator:
Provides you with the Health.Builder instance so you don't need to create one manually
Wraps doHealthCheck(builder) call with try-catch, that returns status DOWN if your healthcheck has failed with exception.
So in general the AbstractHealthIndicator is more convenient to use as you can skip error handling. Choose implementing raw HealthIndicator when you need to provide custom status details on exception.
For example of Zookeeper Health Indicator please refer to existing one provided with spring-cloud-zookeeper https://github.com/spring-cloud/spring-cloud-zookeeper/blob/master/spring-cloud-zookeeper-core/src/main/java/org/springframework/cloud/zookeeper/ZookeeperHealthIndicator.java
Regarding the endpoint /actuator/health/zookeeper, I suggest you to use new feature introduced in SpringBoot 2.2.0 called Health Indicator Groups https://spring.io/blog/2019/10/16/spring-boot-2-2-0#health-indicator-groups
In short, if you use component scan and named custom health indicator MyZookeeperHealthIndicator, then add following properties to register it under custom zookeeper group:
management.endpoint.health.group.zookeeper.include=myZookeeper
After that, custom health details will be displayed under myZookeeper component at /actuator/health/zookeeper
Check following docs for more information:
Writing Custom HealthIndicators https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-features.html#writing-custom-healthindicators
Health Groups https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-features.html#health-groups