A spring boot actuator application, to demonstrate how to aggregate the reactive health of my microservices statuses under the central Edge or API Gateway Server.

I spent a fair amount of my time to understand how to migrate from old deprecated health aggregators APIs like HealthAggregator, DefaultReactiveHealthIndicatorRegistry, and CompositeReactiveHealthIndicator to new ones in the latest spring framework version 5.2.5, and the following application shows how to achieve that.

Note: in the code example, both old way (method with name oldCoreServices()) of aggregating health, and the new way (method with name coreServicesHealth()); both are working when you run the application. You should use new method :)

Make sure that you use Java SE 14.

This application uses the latest version of Spring boot version 2.3.0.M4 so there is no deprecated APIs. Beside I uses Reactive web using WebFlux.

1. Run application from your favorite IDE, or maven as the following:

   λ mvn spring-boot:run -Dspring-boot.run.jvmArguments="--enable-preview"

2. It will run and application listens to port 9090.

3. Open your browser and paste this link or click it http://localhost:9090/actuator/health and you should see something like this:

   {
      "status":"DOWN", [[1]]
      "components":{
         "Core System Microservices":{ [[2]]
            "status":"DOWN",
            "components":{
               "Product Service":{
                  "status":"UP"
               },
               "Recommendation Service":{
                  "status":"DOWN",
                  "details":{
                     "error":"java.lang.IllegalStateException: Not working"
                  }
               },
               "Review Service":{
                  "status":"UP"
               }
            }
         },
         "Old API- Core Services":{ [[3]]
            "status":"DOWN",
            "details":{
               "Review Service":{
                  "status":"UP"
               },
               "Product Service":{
                  "status":"UP"
               },
               "Recommendation Service":{
                  "status":"DOWN",
                  "details":{
                     "error":"java.lang.IllegalStateException: Not working"
                  }
               }
            }
         },
         "diskSpace":{
            "status":"UP",
            "details":{
               "total":255382777856,
               "free":86618931200,
               "threshold":10485760,
               "exists":true
            }
         },
         "ping":{
            "status":"UP"
         }
      }
   }

1. [[1]]: General status of the service is DOWN because one of sub-services are down status.
2. [[2]]: New implementation shows up in the health tree with name "Core System Microservices".
3. [[3]]: Old implementation also shows up in the tree with the name "Old API- Core Services".

Happy coding :)

Copyright (C) 2020 Mohamed Taman Licensed under the MIT License.