Starting to experiment with flow tracking.
diff --git a/core/net/src/main/java/org/onlab/onos/net/intent/impl/FlowTracker.java b/core/net/src/main/java/org/onlab/onos/net/intent/impl/FlowTracker.java
new file mode 100644
index 0000000..8f4a5c7
--- /dev/null
+++ b/core/net/src/main/java/org/onlab/onos/net/intent/impl/FlowTracker.java
@@ -0,0 +1,130 @@
+package org.onlab.onos.net.intent.impl;
+
+import com.google.common.collect.HashMultimap;
+import com.google.common.collect.SetMultimap;
+import org.apache.felix.scr.annotations.Activate;
+import org.apache.felix.scr.annotations.Component;
+import org.apache.felix.scr.annotations.Deactivate;
+import org.apache.felix.scr.annotations.Reference;
+import org.apache.felix.scr.annotations.ReferenceCardinality;
+import org.apache.felix.scr.annotations.Service;
+import org.onlab.onos.event.Event;
+import org.onlab.onos.net.Link;
+import org.onlab.onos.net.LinkKey;
+import org.onlab.onos.net.intent.IntentId;
+import org.onlab.onos.net.link.LinkEvent;
+import org.onlab.onos.net.topology.TopologyEvent;
+import org.onlab.onos.net.topology.TopologyListener;
+import org.onlab.onos.net.topology.TopologyService;
+import org.slf4j.Logger;
+
+import java.util.Collection;
+import java.util.concurrent.ExecutorService;
+
+import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.common.base.Preconditions.checkNotNull;
+import static com.google.common.collect.Multimaps.synchronizedSetMultimap;
+import static java.util.concurrent.Executors.newSingleThreadExecutor;
+import static org.onlab.util.Tools.namedThreads;
+import static org.slf4j.LoggerFactory.getLogger;
+
+/**
+ * Entity responsible for tracking installed flows and for monitoring topology
+ * events to determine what flows are affected by topology changes.
+ */
+@Component
+@Service
+public class FlowTracker implements FlowTrackerService {
+
+ private final Logger log = getLogger(getClass());
+
+ private final SetMultimap<LinkKey, IntentId> intentsByLink =
+ synchronizedSetMultimap(HashMultimap.<LinkKey, IntentId>create());
+
+ @Reference(cardinality = ReferenceCardinality.MANDATORY_UNARY)
+ protected TopologyService topologyService;
+
+ private ExecutorService executorService =
+ newSingleThreadExecutor(namedThreads("onos-flowtracker"));
+
+ private TopologyListener listener = new InternalTopologyListener();
+ private TopologyChangeDelegate delegate;
+
+ @Activate
+ public void activate() {
+ topologyService.addListener(listener);
+ log.info("Started");
+ }
+
+ @Deactivate
+ public void deactivate() {
+ topologyService.removeListener(listener);
+ log.info("Stopped");
+ }
+
+ @Override
+ public void setDelegate(TopologyChangeDelegate delegate) {
+ checkNotNull(delegate, "Delegate cannot be null");
+ checkArgument(this.delegate == null || this.delegate == delegate,
+ "Another delegate already set");
+ this.delegate = delegate;
+ }
+
+ @Override
+ public void unsetDelegate(TopologyChangeDelegate delegate) {
+ checkArgument(this.delegate == delegate, "Not the current delegate");
+ this.delegate = null;
+ }
+
+ @Override
+ public void addTrackedResources(IntentId intentId, Collection<Link> resources) {
+ for (Link link : resources) {
+ intentsByLink.put(new LinkKey(link), intentId);
+ }
+ }
+
+ @Override
+ public void removeTrackedResources(IntentId intentId, Collection<Link> resources) {
+ for (Link link : resources) {
+ intentsByLink.remove(new LinkKey(link), intentId);
+ }
+ }
+
+ // Internal re-actor to topology change events.
+ private class InternalTopologyListener implements TopologyListener {
+ @Override
+ public void event(TopologyEvent event) {
+ executorService.execute(new TopologyChangeHandler(event));
+ }
+ }
+
+ // Re-dispatcher of topology change events.
+ private class TopologyChangeHandler implements Runnable {
+
+ private final TopologyEvent event;
+
+ TopologyChangeHandler(TopologyEvent event) {
+ this.event = event;
+ }
+
+ @Override
+ public void run() {
+ if (event.reasons() == null) {
+ delegate.bumpIntents(intentsByLink.values());
+ } else {
+ for (Event reason : event.reasons()) {
+ if (reason instanceof LinkEvent) {
+ LinkEvent linkEvent = (LinkEvent) reason;
+ if (linkEvent.type() == LinkEvent.Type.LINK_ADDED ||
+ linkEvent.type() == LinkEvent.Type.LINK_UPDATED) {
+ delegate.bumpIntents(intentsByLink.get(new LinkKey(linkEvent.subject())));
+ } else if (linkEvent.type() == LinkEvent.Type.LINK_REMOVED) {
+ delegate.failIntents(intentsByLink.get(new LinkKey(linkEvent.subject())));
+ }
+ }
+ }
+ }
+ }
+ }
+
+}