[ONOS-7818] Implement a device behaviour to get table statistics. Make FlowRuleDriverProvider periodically call FlowRuleProviderService.pushTableStatistics().

Change-Id: Ife2b67b8c6c3582281704afe6f9a90538afbc798
diff --git a/core/api/src/main/java/org/onosproject/net/behaviour/TableStatisticsDiscovery.java b/core/api/src/main/java/org/onosproject/net/behaviour/TableStatisticsDiscovery.java
new file mode 100644
index 0000000..84e6c2b
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/behaviour/TableStatisticsDiscovery.java
@@ -0,0 +1,34 @@
+/*
+ * 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.net.behaviour;
+
+import org.onosproject.net.driver.HandlerBehaviour;
+import org.onosproject.net.flow.TableStatisticsEntry;
+import java.util.Collection;
+
+/**
+ * Behaviour capable of retrieving table statistics from device.
+ */
+public interface TableStatisticsDiscovery extends HandlerBehaviour {
+
+    /**
+     * Returns statistics for all match-action tables currently defined by the device forwarding pipeline.
+     *
+     * @return a list of tableStatisticEntry
+     */
+    Collection<TableStatisticsEntry> getTableStatistics();
+
+}
diff --git a/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleDriverProvider.java b/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleDriverProvider.java
index abda2bf..8a3d724 100644
--- a/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleDriverProvider.java
+++ b/core/net/src/main/java/org/onosproject/net/flow/impl/FlowRuleDriverProvider.java
@@ -16,6 +16,7 @@
 
 package org.onosproject.net.flow.impl;
 
+import static com.google.common.collect.Lists.newArrayList;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.LinkedListMultimap;
 import com.google.common.collect.Multimap;
@@ -25,6 +26,7 @@
 import org.onosproject.mastership.MastershipService;
 import org.onosproject.net.Device;
 import org.onosproject.net.DeviceId;
+import org.onosproject.net.behaviour.TableStatisticsDiscovery;
 import org.onosproject.net.device.DeviceEvent;
 import org.onosproject.net.device.DeviceListener;
 import org.onosproject.net.device.DeviceService;
@@ -35,6 +37,7 @@
 import org.onosproject.net.flow.FlowRuleProgrammable;
 import org.onosproject.net.flow.FlowRuleProvider;
 import org.onosproject.net.flow.FlowRuleProviderService;
+import org.onosproject.net.flow.TableStatisticsEntry;
 import org.onosproject.net.provider.AbstractProvider;
 import org.onosproject.net.provider.ProviderId;
 import org.slf4j.Logger;
@@ -45,6 +48,7 @@
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.ScheduledFuture;
 import java.util.concurrent.TimeUnit;
+import java.util.List;
 
 import static com.google.common.collect.ImmutableSet.copyOf;
 import static java.util.concurrent.Executors.newSingleThreadScheduledExecutor;
@@ -196,12 +200,25 @@
         }
     }
 
+    private void pollTableStatistics(Device device) {
+        try {
+            List<TableStatisticsEntry> tableStatsList = newArrayList(device.as(TableStatisticsDiscovery.class)
+                    .getTableStatistics());
+            providerService.pushTableStatistics(device.id(), tableStatsList);
+        } catch (Exception e) {
+            log.warn("Exception thrown while polling table statistics for {}", device.id(), e);
+        }
+    }
+
     private void pollFlowEntries() {
         try {
             deviceService.getAvailableDevices().forEach(device -> {
                 if (mastershipService.isLocalMaster(device.id()) && device.is(FlowRuleProgrammable.class)) {
                     pollDeviceFlowEntries(device);
                 }
+                if (mastershipService.isLocalMaster(device.id()) && device.is(TableStatisticsDiscovery.class)) {
+                    pollTableStatistics(device);
+                }
             });
         } catch (Exception e) {
             log.warn("Exception thrown while polling flows", e);