add NotificationCallback

src/main/java/rocks/inspectit/gepard/agent/InspectitAgentExtension.java

@@ -30,6 +30,7 @@ public AgentBuilder extend(AgentBuilder agentBuilder, ConfigProperties config) {
 
     boolean successful = NotificationManager.sendStartNotification(SERVER_URL);
     if (successful) log.info("Successfully notified configuration server about start");
+    else log.info("Could not notify configuration server about start");
 
     return agentBuilder;
   }

src/main/java/rocks/inspectit/gepard/agent/notify/NotificationManager.java

@@ -8,10 +8,12 @@
 import org.apache.hc.client5.http.async.methods.SimpleHttpRequest;
 import org.apache.hc.client5.http.async.methods.SimpleHttpResponse;
 import org.apache.hc.client5.http.impl.async.CloseableHttpAsyncClient;
+import org.apache.hc.core5.concurrent.FutureCallback;
 import org.apache.hc.core5.http.HttpResponse;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import rocks.inspectit.gepard.agent.notify.http.HttpClientHolder;
+import rocks.inspectit.gepard.agent.notify.http.NotificationCallback;
 import rocks.inspectit.gepard.agent.notify.http.NotificationFactory;
 
 /** This manager should notify the configuration server about the agent itself and its status. */
@@ -56,7 +58,8 @@ private static boolean doSend(SimpleHttpRequest request)
     if (Objects.isNull(request)) return false;
 
     CloseableHttpAsyncClient client = HttpClientHolder.getClient();
-    Future<SimpleHttpResponse> future = client.execute(request, null);
+    FutureCallback<SimpleHttpResponse> callback = new NotificationCallback();
+    Future<SimpleHttpResponse> future = client.execute(request, callback);
 
     HttpResponse response = future.get();
     return Objects.nonNull(response) && 200 == response.getCode();

src/main/java/rocks/inspectit/gepard/agent/notify/http/NotificationCallback.java

@@ -0,0 +1,26 @@
+package rocks.inspectit.gepard.agent.notify.http;
+
+import org.apache.hc.client5.http.async.methods.SimpleHttpResponse;
+import org.apache.hc.core5.concurrent.FutureCallback;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/** Callback for notifications to the configuration server. Currently, only used for logging. */
+public class NotificationCallback implements FutureCallback<SimpleHttpResponse> {
+  private static final Logger log = LoggerFactory.getLogger(NotificationCallback.class);
+
+  @Override
+  public void completed(SimpleHttpResponse result) {
+    log.info("Notified configuration server and received status code {}", result.getCode());
+  }
+
+  @Override
+  public void failed(Exception ex) {
+    log.error("Failed to notify configuration server", ex);
+  }
+
+  @Override
+  public void cancelled() {
+    log.info("Cancelled notification to configuration server");
+  }
+}