Add new gnmi-standalone driver with fake mastership handling

gNMI does not support mastership. This driver allows controlling gNMI
devices without the need of other mastership-oriented protocols (e.g.
P4Runtime).

Change-Id: I300607fbcc99d3f066904a96e55c9cd954d5d0a5

drivers/gnmi/src/main/java/org/onosproject/drivers/gnmi/GnmiHandshakerStandalone.java

@@ -0,0 +1,117 @@
+/*
+ * Copyright 2019-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.drivers.gnmi;
+
+import com.google.common.collect.Maps;
+import org.onlab.util.SharedExecutors;
+import org.onosproject.gnmi.api.GnmiController;
+import org.onosproject.net.DeviceId;
+import org.onosproject.net.MastershipRole;
+import org.onosproject.net.device.DeviceAgentEvent;
+import org.onosproject.net.device.DeviceAgentListener;
+import org.onosproject.net.device.DeviceHandshaker;
+import org.onosproject.net.provider.ProviderId;
+
+import java.util.TimerTask;
+import java.util.concurrent.ConcurrentMap;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * Implementation of DeviceHandshaker that allows using the gNMI driver as a
+ * standalone one. Since gNMI does not support mastership, this driver stores a
+ * copy of the agent listeners registered by the providers, needed to
+ * acknowledge whatever role was requested.
+ */
+public class GnmiHandshakerStandalone
+        extends GnmiHandshaker implements DeviceHandshaker {
+
+    private static final int ROLE_REPLY_LATENCY_MILLIS = 200;
+    private static final ConcurrentMap<DeviceId, ConcurrentMap<ProviderId, DeviceAgentListener>>
+            AGENT_LISTENERS = Maps.newConcurrentMap();
+    private static final ConcurrentMap<DeviceId, MastershipRole>
+            ROLES = Maps.newConcurrentMap();
+
+    @Override
+    public void roleChanged(MastershipRole newRole) {
+        final DeviceAgentEvent.Type eventType;
+        switch (newRole) {
+            case MASTER:
+                eventType = DeviceAgentEvent.Type.ROLE_MASTER;
+                break;
+            case STANDBY:
+                eventType = DeviceAgentEvent.Type.ROLE_STANDBY;
+                break;
+            case NONE:
+                eventType = DeviceAgentEvent.Type.ROLE_NONE;
+                break;
+            default:
+                log.error("Unrecognized mastership role {}", newRole);
+                return;
+        }
+        SharedExecutors.getTimer().schedule(new TimerTask() {
+            @Override
+            public void run() {
+                if (newRole == MastershipRole.NONE) {
+                    ROLES.remove(deviceId);
+                } else {
+                    ROLES.put(data().deviceId(), newRole);
+                }
+                postAgentEvent(new DeviceAgentEvent(
+                        eventType, data().deviceId()));
+            }
+        }, ROLE_REPLY_LATENCY_MILLIS);
+    }
+
+    @Override
+    public MastershipRole getRole() {
+        return ROLES.getOrDefault(data().deviceId(), MastershipRole.NONE);
+    }
+
+    @Override
+    public void addDeviceAgentListener(ProviderId providerId, DeviceAgentListener listener) {
+        handler().get(GnmiController.class)
+                .addDeviceAgentListener(data().deviceId(), providerId, listener);
+        AGENT_LISTENERS.putIfAbsent(deviceId, Maps.newConcurrentMap());
+        AGENT_LISTENERS.get(deviceId).put(providerId, listener);
+    }
+
+    @Override
+    public void removeDeviceAgentListener(ProviderId providerId) {
+        handler().get(GnmiController.class)
+                .removeDeviceAgentListener(data().deviceId(), providerId);
+        AGENT_LISTENERS.computeIfPresent(deviceId, (did, listeners) -> {
+            listeners.remove(providerId);
+            return listeners.isEmpty() ? null : listeners;
+        });
+    }
+
+    private void postAgentEvent(DeviceAgentEvent event) {
+        checkNotNull(event);
+        if (AGENT_LISTENERS.containsKey(event.subject())) {
+            AGENT_LISTENERS.get(event.subject()).values()
+                    .forEach(l -> l.event(event));
+        }
+    }
+
+    @Override
+    public void disconnect() {
+        ROLES.remove(data().deviceId());
+        AGENT_LISTENERS.remove(data().deviceId());
+        super.disconnect();
+    }
+}

drivers/gnmi/src/main/resources/gnmi-drivers.xml

@@ -15,7 +15,7 @@
   ~ limitations under the License.
   -->
 <drivers>
-    <driver name="gnmi" manufacturer="gnmi" hwVersion="master" swVersion="master">
+    <driver name="gnmi" manufacturer="Unknown" hwVersion="Unknown" swVersion="Unknown">
         <behaviour api="org.onosproject.net.device.DeviceDescriptionDiscovery"
                    impl="org.onosproject.drivers.gnmi.OpenConfigGnmiDeviceDescriptionDiscovery"/>
         <behaviour api="org.onosproject.net.device.DeviceHandshaker"
@@ -25,5 +25,11 @@
         <behaviour api="org.onosproject.net.behaviour.PortAdmin"
                    impl="org.onosproject.drivers.gnmi.OpenConfigGnmiPortAdminBehaviour"/>
     </driver>
+
+    <driver name="gnmi-standalone" manufacturer="Unknown" hwVersion="Unknown"
+            swVersion="Unknown" extends="gnmi">
+        <behaviour api="org.onosproject.net.device.DeviceHandshaker"
+                   impl="org.onosproject.drivers.gnmi.GnmiHandshakerStandalone"/>
+    </driver>
 </drivers>