Merge pull request #739 from aureamunoz/custom-expiration-snippet

Add custom expiration policy for cache snippet to the doc

docs/docs/service-discovery/custom-service-discovery.md

@@ -150,4 +150,10 @@ If you want to customize the expiration strategy, you need:
 1. Implement the `cache` method where the expiration strategy should be defined.
 2. Invalidate the cache when expiration condition evaluates to true.
 
-Take a look to the [Kubernetes Service Discovery](kubernetes.md#Caching the service instances) for further details about this feature.
+Look at the example bellow:
+
+```java linenums="1"
+{{ insert('examples/CustomExpirationCachedAcmeServiceDiscovery.java') }}
+```
+
+Additionally, you can check the [Kubernetes Service Discovery](kubernetes.md#Caching the service instances) for further details about an event-based invalidation example.

docs/snippets/examples/CustomExpirationCachedAcmeServiceDiscovery.java

@@ -0,0 +1,44 @@
+package examples;
+
+import io.smallrye.mutiny.Uni;
+import io.smallrye.stork.api.ServiceInstance;
+import io.smallrye.stork.impl.CachingServiceDiscovery;
+import io.smallrye.stork.impl.DefaultServiceInstance;
+import io.smallrye.stork.utils.ServiceInstanceIds;
+
+import java.util.Collections;
+import java.util.List;
+import java.util.concurrent.atomic.AtomicBoolean;
+
+public class CustomExpirationCachedAcmeServiceDiscovery extends CachingServiceDiscovery {
+
+    private final String host;
+    private final int port;
+
+    private AtomicBoolean invalidated = new AtomicBoolean();
+
+    public CustomExpirationCachedAcmeServiceDiscovery(CachedAcmeConfiguration configuration) {
+        super(configuration.getRefreshPeriod());
+        this.host = configuration.getHost();
+        this.port = Integer.parseInt(configuration.getPort());
+    }
+
+    @Override
+    public Uni<List<ServiceInstance>> fetchNewServiceInstances(List<ServiceInstance> previousInstances) {
+        // Retrieve services...
+        DefaultServiceInstance instance =
+                new DefaultServiceInstance(ServiceInstanceIds.next(), host, port, false);
+        return Uni.createFrom().item(() -> Collections.singletonList(instance));
+    }
+
+    @Override
+    public Uni<List<ServiceInstance>> cache(Uni<List<ServiceInstance>> uni) {
+        return uni.memoize().until(() -> invalidated.get());
+    }
+
+    //command-based cache invalidation: user triggers the action to invalidate the cache.
+    public void invalidate() {
+        invalidated.set(true);
+    }
+
+}