1 files changed, 109 insertions, 0 deletions
diff --git a/infra/notification/impl/src/main/java/io/fd/honeycomb/notification/impl/NotificationProducerTracker.java b/infra/notification/impl/src/main/java/io/fd/honeycomb/notification/impl/NotificationProducerTracker.java
new file mode 100644
index 000000000..808512c21
--- /dev/null
+++ b/infra/notification/impl/src/main/java/io/fd/honeycomb/notification/impl/NotificationProducerTracker.java
@@ -0,0 +1,109 @@
+/*
+ * Copyright (c) 2016 Cisco and/or its affiliates.
+ *
+ * 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.
+ */
+package io.fd.honeycomb.notification.impl;
+
+import static com.google.common.base.Preconditions.checkState;
+
+import com.google.common.collect.Sets;
+import io.fd.honeycomb.notification.ManagedNotificationProducer;
+import io.fd.honeycomb.notification.NotificationCollector;
+import java.util.HashSet;
+import java.util.Set;
+import java.util.stream.Collectors;
+import javax.annotation.Nonnull;
+import javax.annotation.concurrent.ThreadSafe;
+import org.opendaylight.controller.md.sal.dom.spi.DOMNotificationSubscriptionListener;
+import org.opendaylight.controller.md.sal.dom.spi.DOMNotificationSubscriptionListenerRegistry;
+import org.opendaylight.yangtools.concepts.ListenerRegistration;
+import org.opendaylight.yangtools.yang.common.QName;
+import org.opendaylight.yangtools.yang.model.api.SchemaPath;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Starts & stops notification producer dependencies on demand.
+ * Uses {@link DOMNotificationSubscriptionListenerRegistry} to receive subscription change notifications.
+ */
+@ThreadSafe
+public final class NotificationProducerTracker
+    implements DOMNotificationSubscriptionListener, AutoCloseable {
+
+    private static final Logger LOG = LoggerFactory.getLogger(NotificationProducerTracker.class);
+
+    private final ListenerRegistration<NotificationProducerTracker> subscriptionListener;
+    private final NotificationProducerRegistry registry;
+    private final NotificationCollector collector;
+
+    private final Set<ManagedNotificationProducer> alreadyStartedProducers = new HashSet<>();
+
+    public NotificationProducerTracker(@Nonnull final NotificationProducerRegistry registry,
+                                       @Nonnull final NotificationCollector collector,
+                                       @Nonnull final DOMNotificationSubscriptionListenerRegistry notificationRouter) {
+        this.registry = registry;
+        this.collector = collector;
+        this.subscriptionListener = notificationRouter.registerSubscriptionListener(this);
+    }
+
+    @Override
+    public synchronized void onSubscriptionChanged(final Set<SchemaPath> set) {
+        LOG.debug("Subscriptions changed. Current subscriptions: {}", set);
+        final Set<QName> currentSubscriptions = set.stream().map(SchemaPath::getLastComponent).collect(Collectors.toSet());
+        final Set<QName> startedQNames = getStartedQNames(alreadyStartedProducers);
+        final Sets.SetView<QName> newSubscriptions = Sets.difference(currentSubscriptions, startedQNames);
+        LOG.debug("Subscriptions changed. New subscriptions: {}", newSubscriptions);
+        final Sets.SetView<QName> deletedSubscriptions = Sets.difference(startedQNames, currentSubscriptions);
+        LOG.debug("Subscriptions changed. Deleted subscriptions: {}", deletedSubscriptions);
+
+        newSubscriptions.stream().forEach(newSub -> {
+            if(!registry.getNotificationQNameToProducer().containsKey(newSub)) {
+                return;
+            }
+            final ManagedNotificationProducer producer = registry.getNotificationQNameToProducer().get(newSub);
+            if(alreadyStartedProducers.contains(producer)) {
+                return;
+            }
+            LOG.debug("Starting notification producer: {}", producer);
+            producer.start(collector);
+            alreadyStartedProducers.add(producer);
+        });
+
+        deletedSubscriptions.stream().forEach(newSub -> {
+            checkState(registry.getNotificationQNameToProducer().containsKey(newSub));
+            final ManagedNotificationProducer producer = registry.getNotificationQNameToProducer().get(newSub);
+            checkState(alreadyStartedProducers.contains(producer));
+            LOG.debug("Stopping notification producer: {}", producer);
+            producer.stop();
+            alreadyStartedProducers.remove(producer);
+        });
+
+    }
+
+    private Set<QName> getStartedQNames(final Set<ManagedNotificationProducer> alreadyStartedProducers) {
+        return alreadyStartedProducers.stream()
+            .flatMap(p -> registry.getNotificationProducerQNames().get(p).stream())
+            .collect(Collectors.toSet());
+    }
+
+    @Override
+    public synchronized void close() throws Exception {
+        LOG.trace("Closing");
+        subscriptionListener.close();
+        // Stop all producers
+        LOG.debug("Stopping all producers: {}", alreadyStartedProducers);
+        alreadyStartedProducers.forEach(ManagedNotificationProducer::stop);
+        alreadyStartedProducers.clear();
+    }
+}