Springboot application with admin server and application that uses EhCache

Admin server is only used to display metrics in a nicer, more human readable way. This app is also a service registry. It loads all the necessary dependencies for it through spring-boot-admin dependency. You can read more about Codecentric's Admin Server here.

Demo application is a simple app that has only two endpoints, one that serves cached data and one that doesn't.

http://localhost:8081/api/demo - not cached

http://localhost:8081/api/demo/cached - cached data

For demo purposes I have used Fake Response API that has a possibility to set the amount of time you would like the response to be delayed which is perfect for testing caching of your API.

Example: http://www.fakeresponse.com/api/?sleep=3

Starting the apps

If you don't have maven installed, I recommend you to follow this step-by-step tutorial.

Clone the repo and go to ehcache-spring-metrics folder. If you use IntelliJ, then just start AdminApplication and DemoApplication. Configurations for IntelliJ are already included. If you want to start it from your terminal, run: mvn install Then start admin application by running mvn spring-boot:run -pl admin and open your browser on http://localhost:8080. Open a new terminal go to the root of the project and run mvn spring-boot:run -pl application and open your browser on http://localhost:8081. You suppose to get Spring's Whitelabel Error page (404), if you didn't, well you did something wrong, just try again.

Actual usage

Test the endpoint that I have mentioned above. The not-cached endpoint has sleep for 3 seconds as well as cached one when you hit it for the first time, after that endpoint with cached data will return response in a couple of milliseconds.

EhCache configuration

All of ehcache configuration can be found in ehcache.xml in resource folder. Statistics are enabled and cache alias for cached data is defined as fakeSlowData. One thing left is the annotation that will say what data to cache. Open DemoService class and look for the method getCachedData. It has @Cacheable("fakeSlowData") annotation that say that data returned from that function will be cached with alias fakeSlowData.

Metrics

1. In order to see the metrics, first you have to have cached data, so first fire a http request to http://localhost:8081/api/demo/cached.
2. Open admin app and go to the metrics tab.
3. You will see a block with title cache which contains hit and miss ratio. Hit and miss ratio will update each time you send a request to /cached endpoint.

Keep in mind that in ehcache.xml cache has expiry set for 10 seconds, that means that after 10 seconds cache with alias fakeSlowData will become empty and http request to FakeResponseAPI will be sent again in order to get new data to cache.