Add gNMI device state subscriber

Change-Id: I20cb5e130f4e416bf8678aab2e5268faf24ad06b
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClient.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClient.java
index 5beb238..6e65dd3 100644
--- a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClient.java
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiClient.java
@@ -22,6 +22,7 @@
 import gnmi.Gnmi.GetResponse;
 import gnmi.Gnmi.SetRequest;
 import gnmi.Gnmi.SetResponse;
+import gnmi.Gnmi.SubscribeRequest;
 import org.onosproject.grpc.api.GrpcClient;
 
 import java.util.concurrent.CompletableFuture;
@@ -56,12 +57,23 @@
     CompletableFuture<SetResponse> set(SetRequest request);
 
     /**
-     * Check weather the gNMI service is available or not by sending a
-     * dummy get request message.
+     * Subscribes to a given specific gNMI path.
+     *
+     * @param request the subscribe request
+     * @return true if subscribe successfully; false otherwise
+     */
+    boolean subscribe(SubscribeRequest request);
+
+    /**
+     * Terminates the subscription channel of this device.
+     */
+    void terminateSubscriptionChannel();
+
+    /**
+     * Check weather the gNMI service is available or not by sending a dummy get
+     * request message.
      *
      * @return true if gNMI service available; false otherwise
      */
     CompletableFuture<Boolean> isServiceAvailable();
-
-    // TODO: Support gNMI subscription
 }
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiController.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiController.java
index f4964ed..b0e0071 100644
--- a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiController.java
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiController.java
@@ -17,6 +17,7 @@
 package org.onosproject.gnmi.api;
 
 import com.google.common.annotations.Beta;
+import org.onosproject.event.ListenerService;
 import org.onosproject.grpc.api.GrpcClientController;
 
 /**
@@ -24,5 +25,6 @@
  */
 @Beta
 public interface GnmiController
-        extends GrpcClientController<GnmiClientKey, GnmiClient> {
+        extends GrpcClientController<GnmiClientKey, GnmiClient>,
+        ListenerService<GnmiEvent, GnmiEventListener> {
 }
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEvent.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEvent.java
index 5129926..84031d0 100644
--- a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEvent.java
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiEvent.java
@@ -32,15 +32,10 @@
         /**
          * Update.
          */
-        UPDATE,
-
-        /**
-         * Sync response.
-         */
-        SYNC_RESPONSE
+        UPDATE
     }
 
-    protected GnmiEvent(Type type, GnmiEventSubject subject) {
+    public GnmiEvent(Type type, GnmiEventSubject subject) {
         super(type, subject);
     }
 }
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiUpdate.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiUpdate.java
new file mode 100644
index 0000000..eeb7649
--- /dev/null
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiUpdate.java
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * 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 org.onosproject.gnmi.api;
+
+import com.google.common.base.MoreObjects;
+import gnmi.Gnmi.Notification;
+import org.onosproject.net.DeviceId;
+
+/**
+ * Event class for gNMI update.
+ */
+public class GnmiUpdate implements GnmiEventSubject {
+    private DeviceId deviceId;
+    private Notification update;
+    private boolean syncResponse;
+
+    /**
+     * Default constructor.
+     *
+     * @param deviceId the device id for this event
+     * @param update the update for this event
+     * @param syncResponse indicate target has sent all values associated with
+     *                     the subscription at least once.
+     */
+    public GnmiUpdate(DeviceId deviceId, Notification update, boolean syncResponse) {
+        this.deviceId = deviceId;
+        this.update = update;
+        this.syncResponse = syncResponse;
+    }
+
+    /**
+     * Gets the update data.
+     *
+     * @return the update data
+     */
+    public Notification update() {
+        return update;
+    }
+
+    /**
+     * indicate target has sent all values associated with the subscription at
+     * least once.
+     *
+     * @return true if all value from target has sent
+     */
+    public boolean syncResponse() {
+        return syncResponse;
+    }
+
+    @Override
+    public DeviceId deviceId() {
+        return deviceId;
+    }
+
+    @Override
+    public String toString() {
+        return MoreObjects.toStringHelper(getClass())
+                .add("deviceId", deviceId)
+                .add("syncResponse", syncResponse)
+                .add("update", update)
+                .toString();
+    }
+}
diff --git a/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiUtils.java b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiUtils.java
new file mode 100644
index 0000000..6a71a19
--- /dev/null
+++ b/protocols/gnmi/api/src/main/java/org/onosproject/gnmi/api/GnmiUtils.java
@@ -0,0 +1,55 @@
+/*
+ * Copyright 2018-present Open Networking Foundation
+ *
+ * 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 org.onosproject.gnmi.api;
+
+import gnmi.Gnmi.Path;
+
+import java.util.List;
+import java.util.stream.Collectors;
+
+/**
+ * Utilities for gNMI protocol.
+ */
+public final class GnmiUtils {
+
+    private GnmiUtils() {
+        // Hide default constructor
+    }
+
+    /**
+     * Convert gNMI path to human readable string.
+     *
+     * @param path the gNMI path
+     * @return readable string of the path
+     */
+    public static String pathToString(Path path) {
+        StringBuilder pathStringBuilder = new StringBuilder();
+
+        path.getElemList().forEach(elem -> {
+            pathStringBuilder.append("/").append(elem.getName());
+            if (elem.getKeyCount() > 0) {
+                pathStringBuilder.append("[");
+                List<String> keys = elem.getKeyMap().entrySet().stream()
+                        .map(entry -> entry.getKey() + "=" + entry.getValue())
+                        .collect(Collectors.toList());
+                pathStringBuilder.append(String.join(", ", keys));
+                pathStringBuilder.append("]");
+            }
+        });
+        return pathStringBuilder.toString();
+    }
+}
diff --git a/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiClientImpl.java b/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiClientImpl.java
index 22b226b..117b27e 100644
--- a/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiClientImpl.java
+++ b/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiClientImpl.java
@@ -23,17 +23,26 @@
 import gnmi.Gnmi.PathElem;
 import gnmi.Gnmi.SetRequest;
 import gnmi.Gnmi.SetResponse;
+import gnmi.Gnmi.SubscribeRequest;
+import gnmi.Gnmi.SubscribeResponse;
 import gnmi.gNMIGrpc;
 import io.grpc.ManagedChannel;
 import io.grpc.Status;
 import io.grpc.StatusRuntimeException;
+import io.grpc.stub.ClientCallStreamObserver;
+import io.grpc.stub.StreamObserver;
 import org.onosproject.gnmi.api.GnmiClient;
 import org.onosproject.gnmi.api.GnmiClientKey;
+import org.onosproject.gnmi.api.GnmiEvent;
+import org.onosproject.gnmi.api.GnmiUpdate;
 import org.onosproject.grpc.ctl.AbstractGrpcClient;
 import org.slf4j.Logger;
 
+import java.net.ConnectException;
 import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.atomic.AtomicBoolean;
 
+import static java.lang.String.format;
 import static org.slf4j.LoggerFactory.getLogger;
 
 /**
@@ -45,10 +54,14 @@
     private static final GetRequest DUMMY_REQUEST = GetRequest.newBuilder().addPath(DUMMY_PATH).build();
     private final Logger log = getLogger(getClass());
     private final gNMIGrpc.gNMIBlockingStub blockingStub;
+    private StreamChannelManager streamChannelManager;
+    private GnmiControllerImpl controller;
 
-    GnmiClientImpl(GnmiClientKey clientKey, ManagedChannel managedChannel) {
+    GnmiClientImpl(GnmiClientKey clientKey, ManagedChannel managedChannel, GnmiControllerImpl controller) {
         super(clientKey);
         this.blockingStub = gNMIGrpc.newBlockingStub(managedChannel);
+        this.streamChannelManager = new StreamChannelManager(managedChannel);
+        this.controller = controller;
     }
 
     @Override
@@ -67,10 +80,26 @@
     }
 
     @Override
+    public boolean subscribe(SubscribeRequest request) {
+        return streamChannelManager.send(request);
+    }
+
+    @Override
+    public void terminateSubscriptionChannel() {
+        streamChannelManager.complete();
+    }
+
+    @Override
     public CompletableFuture<Boolean> isServiceAvailable() {
         return supplyInContext(this::doServiceAvailable, "isServiceAvailable");
     }
 
+    @Override
+    protected Void doShutdown() {
+        streamChannelManager.complete();
+        return super.doShutdown();
+    }
+
     private CapabilityResponse doCapability() {
         CapabilityRequest request = CapabilityRequest.newBuilder().build();
         try {
@@ -110,4 +139,121 @@
             return e.getStatus().getCode().equals(Status.Code.INVALID_ARGUMENT);
         }
     }
+
+
+
+    /**
+     * A manager for the gNMI stream channel that opportunistically creates
+     * new stream RCP stubs (e.g. when one fails because of errors) and posts
+     * subscribe events via the gNMI controller.
+     */
+    private final class StreamChannelManager {
+
+        private final ManagedChannel channel;
+        private final AtomicBoolean open;
+        private final StreamObserver<SubscribeResponse> responseObserver;
+        private ClientCallStreamObserver<SubscribeRequest> requestObserver;
+
+        private StreamChannelManager(ManagedChannel channel) {
+            this.channel = channel;
+            this.responseObserver = new InternalStreamResponseObserver(this);
+            this.open = new AtomicBoolean(false);
+        }
+
+        private void initIfRequired() {
+            if (requestObserver == null) {
+                log.debug("Creating new stream channel for {}...", deviceId);
+                requestObserver = (ClientCallStreamObserver<SubscribeRequest>)
+                        gNMIGrpc.newStub(channel).subscribe(responseObserver);
+                open.set(false);
+            }
+        }
+
+        public boolean send(SubscribeRequest value) {
+            synchronized (this) {
+                initIfRequired();
+                try {
+                    requestObserver.onNext(value);
+                    return true;
+                } catch (Throwable ex) {
+                    if (ex instanceof StatusRuntimeException) {
+                        log.warn("Unable to send subscribe request to {}: {}",
+                                deviceId, ex.getMessage());
+                    } else {
+                        log.warn("Exception while sending subscribe request to {}",
+                                deviceId, ex);
+                    }
+                    complete();
+                    return false;
+                }
+            }
+        }
+
+        public void complete() {
+            synchronized (this) {
+                if (requestObserver != null) {
+                    requestObserver.onCompleted();
+                    requestObserver.cancel("Terminated", null);
+                    requestObserver = null;
+                }
+            }
+        }
+    }
+
+
+    /**
+     * Handles messages received from the device on the stream channel.
+     */
+    private final class InternalStreamResponseObserver
+            implements StreamObserver<SubscribeResponse> {
+
+        private final StreamChannelManager streamChannelManager;
+
+        private InternalStreamResponseObserver(
+                StreamChannelManager streamChannelManager) {
+            this.streamChannelManager = streamChannelManager;
+        }
+
+        @Override
+        public void onNext(SubscribeResponse message) {
+            executorService.submit(() -> doNext(message));
+        }
+
+        private void doNext(SubscribeResponse message) {
+            try {
+                log.debug("Received message on stream channel from {}: {}",
+                        deviceId, message.toString());
+                GnmiUpdate update = new GnmiUpdate(deviceId, message.getUpdate(), message.getSyncResponse());
+                GnmiEvent event = new GnmiEvent(GnmiEvent.Type.UPDATE, update);
+                controller.postEvent(event);
+            } catch (Throwable ex) {
+                log.error("Exception while processing stream message from {}",
+                        deviceId, ex);
+            }
+        }
+
+        @Override
+        public void onError(Throwable throwable) {
+            if (throwable instanceof StatusRuntimeException) {
+                StatusRuntimeException sre = (StatusRuntimeException) throwable;
+                if (sre.getStatus().getCause() instanceof ConnectException) {
+                    log.warn("Device {} is unreachable ({})",
+                            deviceId, sre.getCause().getMessage());
+                } else {
+                    log.warn("Received error on stream channel for {}: {}",
+                            deviceId, throwable.getMessage());
+                }
+            } else {
+                log.warn(format("Received exception on stream channel for %s",
+                        deviceId), throwable);
+            }
+            streamChannelManager.complete();
+        }
+
+        @Override
+        public void onCompleted() {
+            log.warn("Stream channel for {} has completed", deviceId);
+            streamChannelManager.complete();
+        }
+    }
 }
diff --git a/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiControllerImpl.java b/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiControllerImpl.java
index 8392c4a..cf14712 100644
--- a/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiControllerImpl.java
+++ b/protocols/gnmi/ctl/src/main/java/org/onosproject/gnmi/ctl/GnmiControllerImpl.java
@@ -41,6 +41,7 @@
     @Activate
     public void activate() {
         super.activate();
+        eventDispatcher.addSink(GnmiEvent.class, listenerRegistry);
         log.info("Started");
     }
 
@@ -52,6 +53,15 @@
 
     @Override
     protected GnmiClient createClientInstance(GnmiClientKey clientKey, ManagedChannel channel) {
-        return new GnmiClientImpl(clientKey, channel);
+        return new GnmiClientImpl(clientKey, channel, this);
+    }
+
+    /**
+     * Handles event from gNMI client.
+     *
+     * @param event the gNMI event
+     */
+    void postEvent(GnmiEvent event) {
+        post(event);
     }
 }