1 files changed, 105 insertions, 0 deletions
diff --git a/src/main/java/org/onap/dcae/ApplicationConfigurationListener.java b/src/main/java/org/onap/dcae/ApplicationConfigurationListener.java
new file mode 100644
index 00000000..b86bc1ec
--- /dev/null
+++ b/src/main/java/org/onap/dcae/ApplicationConfigurationListener.java
@@ -0,0 +1,105 @@
+/*-
+ * ============LICENSE_START=======================================================
+ * VES Collector
+ * ================================================================================
+ * Copyright (C) 2020 Nokia. All rights reserved.
+ * ================================================================================
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ * ============LICENSE_END=========================================================
+ */
+
+
+package org.onap.dcae;
+
+import org.onap.dcae.configuration.ConfigurationHandler;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+import reactor.core.Disposable;
+
+import java.time.Duration;
+
+/**
+ * ApplicationConfigurationListener is used to listen at notifications with configuration updates send from Consul.
+ */
+public class ApplicationConfigurationListener implements Runnable {
+
+    private static Logger log = LoggerFactory.getLogger(ApplicationConfigurationListener.class);
+
+    private Duration interval;
+    private boolean terminate = false;
+    private final ConfigurationHandler configurationHandler;
+
+    /**
+     * Constructor
+     * @param interval defines period of time when notification can come
+     * @param configurationHandler handles notifications send by Consul
+     */
+    public ApplicationConfigurationListener(Duration interval, ConfigurationHandler configurationHandler) {
+        this.interval = interval;
+        this.configurationHandler = configurationHandler;
+    }
+
+    /**
+     * Reload listener to start listening for Consul notifications with defined interval.
+     * @param interval defines period of time when notification can come
+     */
+    public synchronized void reload(Duration interval) {
+        this.interval = interval;
+        log.info("Handler configuration was changed. Need to reload configuration handler.");
+        sendReloadAction();
+    }
+
+    synchronized void sendReloadAction() {
+        this.notifyAll();
+    }
+
+    /**
+     * Start listening for Consul notification.
+     */
+    @Override
+    public void run() {
+        Disposable consulListener = null;
+        do {
+            try {
+                consulListener = listenForConfigurationUpdates();
+                synchronized (this) {
+                    log.info("Switch to configuration handler thread. Active waiting for configuration from Consul.");
+                    this.wait();
+                }
+            } catch (Exception e) {
+                log.error("Unexpected error occurred during handling data from Consul.", e);
+                terminate();
+            } finally {
+                stopListeningForConfigurationUpdates(consulListener);
+            }
+        } while (!this.terminate);
+    }
+
+    private Disposable listenForConfigurationUpdates() {
+        return this.configurationHandler.startListen(this.interval);
+    }
+
+    void terminate() {
+        this.terminate = true;
+    }
+
+    /**
+     * Release resources when there is a need to stop listener
+     * @param consulListener Handler to Consul listener
+     */
+    void stopListeningForConfigurationUpdates(Disposable consulListener) {
+        if (consulListener != null) {
+            consulListener.dispose();
+        }
+    }
+}