actuator.adoc

Actuator

1. add maven dependency

   <dependency>
     <groupId>org.springframework.boot</groupId>
     <artifactId>spring-boot-starter-actuator</artifactId>
   </dependency>

2. restart your app to check the following endpoints

   • http://localhost:8080/metrics - app metrics

   • http://localhost:8080/mappings - list all url mappings

3. write your own metrics and health indicator

   @RestController
   class FlipFlopController implements HealthIndicator {
       private final AtomicLong requestCount = new AtomicLong();
       private final CounterService counterService;
   
       FlipFlopController(CounterService counterService) {
           this.counterService = counterService;
       }
   
       @Override
       public Health health() {
           long count = requestCount.get();
           return count % 2 == 1
                   ? Health.up().build()
                   : Health.down().withDetail("count", count).build();
       }
   
       @RequestMapping("/metered")
       String metered() {
           counterService.increment("metered.request.count");
           return "ok" + requestCount.incrementAndGet();
       }
   }

4. now restart your app, and go to http://localhost:8080/health (depends on the login, admin can view more details than user). Read the reference when you have time (optional)

   admin view

   {
     "status": "DOWN",
     "flipFlopController": {
       "status": "DOWN",
       "count": 0
     },
     "diskSpace": {
       "status": "UP",
       "total": 499071844352,
       "free": 243076169728,
       "threshold": 10485760
     },
     "db": {
       "status": "UP",
       "database": "H2",
       "hello": 1
     }
   }

5. hit the url http://localhost:8080/metered once and check the health endpoint again

6. hit the url http://localhost:8080/metrics to search for the key metered.request.count

7. (optional) Experiment with more endpoints