Deduplication of the partition change events

@@ -59,6 +59,7 @@ import org.thingsboard.server.queue.discovery.PartitionService;
 import org.thingsboard.server.queue.util.TbCoreComponent;
 import org.thingsboard.server.service.queue.TbClusterService;
 import org.thingsboard.server.service.telemetry.TelemetrySubscriptionService;
+import org.thingsboard.server.utils.EventDeduplicationExecutor;
 
 import javax.annotation.Nullable;
 import javax.annotation.PostConstruct;
@@ -126,13 +127,13 @@ public class DefaultDeviceStateService implements DeviceStateService {
     @Getter
     private int initFetchPackSize;
 
-    private volatile boolean clusterUpdatePending = false;
-
     private ListeningScheduledExecutorService queueExecutor;
     private final ConcurrentMap<TopicPartitionInfo, Set<DeviceId>> partitionedDevices = new ConcurrentHashMap<>();
     private final ConcurrentMap<DeviceId, DeviceStateData> deviceStates = new ConcurrentHashMap<>();
     private final ConcurrentMap<DeviceId, Long> deviceLastReportedActivity = new ConcurrentHashMap<>();
     private final ConcurrentMap<DeviceId, Long> deviceLastSavedActivity = new ConcurrentHashMap<>();
+    private volatile EventDeduplicationExecutor<Set<TopicPartitionInfo>> deduplicationExecutor;
+
 
     public DefaultDeviceStateService(TenantService tenantService, DeviceService deviceService,
                                      AttributesService attributesService, TimeseriesService tsService,
@@ -155,6 +156,7 @@ public class DefaultDeviceStateService implements DeviceStateService {
         // Should be always single threaded due to absence of locks.
         queueExecutor = MoreExecutors.listeningDecorator(Executors.newSingleThreadScheduledExecutor(ThingsBoardThreadFactory.forName("device-state")));
         queueExecutor.scheduleAtFixedRate(this::updateState, new Random().nextInt(defaultStateCheckIntervalInSec), defaultStateCheckIntervalInSec, TimeUnit.SECONDS);
+        deduplicationExecutor = new EventDeduplicationExecutor<>(DefaultDeviceStateService.class.getSimpleName(), queueExecutor, this::initStateFromDB);
     }
 
     @PreDestroy
@@ -292,25 +294,14 @@ public class DefaultDeviceStateService implements DeviceStateService {
         }
     }
 
-    volatile Set<TopicPartitionInfo> pendingPartitions;
-
     @Override
     public void onApplicationEvent(PartitionChangeEvent partitionChangeEvent) {
         if (ServiceType.TB_CORE.equals(partitionChangeEvent.getServiceType())) {
-            synchronized (this) {
-                pendingPartitions = partitionChangeEvent.getPartitions();
-                if (!clusterUpdatePending) {
-                    clusterUpdatePending = true;
-                    queueExecutor.submit(() -> {
-                        clusterUpdatePending = false;
-                        initStateFromDB();
-                    });
-                }
-            }
+            deduplicationExecutor.submit(partitionChangeEvent.getPartitions());
         }
     }
 
-    private void initStateFromDB() {
+    private void initStateFromDB(Set<TopicPartitionInfo> pendingPartitions) {
         try {
             log.info("CURRENT PARTITIONS: {}", partitionedDevices.keySet());
             log.info("NEW PARTITIONS: {}", pendingPartitions);

+/**
+ * Copyright © 2016-2021 The Thingsboard Authors
+ *
+ * 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.thingsboard.server.utils;
+
+import lombok.extern.slf4j.Slf4j;
+
+import java.util.concurrent.Executor;
+import java.util.concurrent.ExecutorService;
+import java.util.function.Consumer;
+
+/**
+ * This class deduplicate executions of the specified function.
+ * Useful in cluster mode, when you get event about partition change multiple times.
+ * Assuming that the function execution is expensive, we should execute it immediately when first time event occurs and
+ * later, once the processing of first event is done, process last pending task.
+ *
+ * @param <P> parameters of the function
+ */
+@Slf4j
+public class EventDeduplicationExecutor<P> {
+    private final String name;
+    private final ExecutorService executor;
+    private final Consumer<P> function;
+    private P pendingTask;
+    private boolean busy;
+
+    public EventDeduplicationExecutor(String name, ExecutorService executor, Consumer<P> function) {
+        this.name = name;
+        this.executor = executor;
+        this.function = function;
+    }
+
+    public void submit(P params) {
+        log.info("[{}] Going to submit: {}", name, params);
+        synchronized (EventDeduplicationExecutor.this) {
+            if (!busy) {
+                busy = true;
+                pendingTask = null;
+                try {
+                    log.info("[{}] Submitting task: {}", name, params);
+                    executor.submit(() -> {
+                        try {
+                            log.info("[{}] Executing task: {}", name, params);
+                            function.accept(params);
+                        } catch (Throwable e) {
+                            log.warn("Failed to process task with parameters: {}", params, e);
+                            throw e;
+                        } finally {
+                            unlockAndProcessIfAny();
+                        }
+                    });
+                } catch (Throwable e) {
+                    log.warn("Failed to submit task with parameters: {}", params, e);
+                    unlockAndProcessIfAny();
+                    throw e;
+                }
+            } else {
+                log.info("[{}] Task is already in progress. {} pending task: {}", name, pendingTask == null ? "adding" : "updating", params);
+                pendingTask = params;
+            }
+        }
+    }
+
+    private void unlockAndProcessIfAny() {
+        synchronized (EventDeduplicationExecutor.this) {
+            busy = false;
+            if (pendingTask != null) {
+                submit(pendingTask);
+            }
+        }
+    }
+}

+/**
+ * Copyright © 2016-2021 The Thingsboard Authors
+ *
+ * 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.thingsboard.server.util;
+
+import com.google.common.util.concurrent.MoreExecutors;
+import lombok.extern.slf4j.Slf4j;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mockito;
+import org.mockito.runners.MockitoJUnitRunner;
+import org.thingsboard.server.utils.EventDeduplicationExecutor;
+
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.function.Consumer;
+
+@Slf4j
+@RunWith(MockitoJUnitRunner.class)
+public class EventDeduplicationExecutorTest {
+
+    @Test
+    public void testSimpleFlowSameThread() throws InterruptedException {
+        simpleFlow(MoreExecutors.newDirectExecutorService());
+    }
+
+    @Test
+    public void testPeriodicFlowSameThread() throws InterruptedException {
+        periodicFlow(MoreExecutors.newDirectExecutorService());
+    }
+
+
+    @Test
+    public void testSimpleFlowSingleThread() throws InterruptedException {
+        simpleFlow(Executors.newFixedThreadPool(1));
+    }
+
+    @Test
+    public void testPeriodicFlowSingleThread() throws InterruptedException {
+        periodicFlow(Executors.newFixedThreadPool(1));
+    }
+
+    @Test
+    public void testSimpleFlowMultiThread() throws InterruptedException {
+        simpleFlow(Executors.newFixedThreadPool(3));
+    }
+
+    @Test
+    public void testPeriodicFlowMultiThread() throws InterruptedException {
+        periodicFlow(Executors.newFixedThreadPool(3));
+    }
+
+    private void simpleFlow(ExecutorService executorService) throws InterruptedException {
+        try {
+            Consumer<String> function = Mockito.spy(StringConsumer.class);
+            EventDeduplicationExecutor<String> executor = new EventDeduplicationExecutor<>(EventDeduplicationExecutorTest.class.getSimpleName(), executorService, function);
+
+            String params1 = "params1";
+            String params2 = "params2";
+            String params3 = "params3";
+
+            executor.submit(params1);
+            executor.submit(params2);
+            executor.submit(params3);
+            Thread.sleep(500);
+            Mockito.verify(function).accept(params1);
+            Mockito.verify(function).accept(params3);
+        } finally {
+            executorService.shutdownNow();
+        }
+    }
+
+    private void periodicFlow(ExecutorService executorService) throws InterruptedException {
+        try {
+            Consumer<String> function = Mockito.spy(StringConsumer.class);
+            EventDeduplicationExecutor<String> executor = new EventDeduplicationExecutor<>(EventDeduplicationExecutorTest.class.getSimpleName(), executorService, function);
+
+            String params1 = "params1";
+            String params2 = "params2";
+            String params3 = "params3";
+
+            executor.submit(params1);
+            Thread.sleep(500);
+            executor.submit(params2);
+            Thread.sleep(500);
+            executor.submit(params3);
+            Thread.sleep(500);
+            Mockito.verify(function).accept(params1);
+            Mockito.verify(function).accept(params2);
+            Mockito.verify(function).accept(params3);
+        } finally {
+            executorService.shutdownNow();
+        }
+    }
+
+    public static class StringConsumer implements Consumer<String> {
+        @Override
+        public void accept(String s) {
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+}