[2.5]fix ConcurrentModificationException (#2560)

* fix ConcurrentModificationException

* kafka consumer improvements

* kafka consumer improvements

* refactored kafka consumer

* refactored kafka consumer

common/queue/src/main/java/org/thingsboard/server/queue/kafka/TBKafkaConsumerTemplate.java

@@ -33,6 +33,8 @@ import java.util.Collections;
 import java.util.List;
 import java.util.Properties;
 import java.util.Set;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReentrantLock;
 import java.util.stream.Collectors;
 
 /**
@@ -46,6 +48,7 @@ public class TBKafkaConsumerTemplate<T extends TbQueueMsg> implements TbQueueCon
     private final TbKafkaDecoder<T> decoder;
     private volatile boolean subscribed;
     private volatile Set<TopicPartitionInfo> partitions;
+    private final Lock consumerLock;
 
     @Getter
     private final String topic;
@@ -71,6 +74,7 @@ public class TBKafkaConsumerTemplate<T extends TbQueueMsg> implements TbQueueCon
         this.consumer = new KafkaConsumer<>(props);
         this.decoder = decoder;
         this.topic = topic;
+        this.consumerLock = new ReentrantLock();
     }
 
     @Override
@@ -94,23 +98,30 @@ public class TBKafkaConsumerTemplate<T extends TbQueueMsg> implements TbQueueCon
                 log.debug("Failed to await subscription", e);
             }
         } else {
-            if (!subscribed) {
-                List<String> topicNames = partitions.stream().map(TopicPartitionInfo::getFullTopicName).collect(Collectors.toList());
-                topicNames.forEach(admin::createTopicIfNotExists);
-                consumer.subscribe(topicNames);
-                subscribed = true;
-            }
-            ConsumerRecords<String, byte[]> records = consumer.poll(Duration.ofMillis(durationInMillis));
-            if (records.count() > 0) {
-                List<T> result = new ArrayList<>();
-                records.forEach(record -> {
-                    try {
-                        result.add(decode(record));
-                    } catch (IOException e) {
-                        log.error("Failed decode record: [{}]", record);
-                    }
-                });
-                return result;
+            try {
+                consumerLock.lock();
+
+                if (!subscribed) {
+                    List<String> topicNames = partitions.stream().map(TopicPartitionInfo::getFullTopicName).collect(Collectors.toList());
+                    topicNames.forEach(admin::createTopicIfNotExists);
+                    consumer.subscribe(topicNames);
+                    subscribed = true;
+                }
+
+                ConsumerRecords<String, byte[]> records = consumer.poll(Duration.ofMillis(durationInMillis));
+                if (records.count() > 0) {
+                    List<T> result = new ArrayList<>();
+                    records.forEach(record -> {
+                        try {
+                            result.add(decode(record));
+                        } catch (IOException e) {
+                            log.error("Failed decode record: [{}]", record);
+                        }
+                    });
+                    return result;
+                }
+            } finally {
+                consumerLock.unlock();
             }
         }
         return Collections.emptyList();
@@ -118,12 +129,25 @@ public class TBKafkaConsumerTemplate<T extends TbQueueMsg> implements TbQueueCon
 
     @Override
     public void commit() {
-        consumer.commitAsync();
+        try {
+            consumerLock.lock();
+            consumer.commitAsync();
+        } finally {
+            consumerLock.unlock();
+        }
     }
 
     @Override
     public void unsubscribe() {
-        consumer.unsubscribe();
+        try {
+            consumerLock.lock();
+            if (consumer != null) {
+                consumer.unsubscribe();
+                consumer.close();
+            }
+        } finally {
+            consumerLock.unlock();
+        }
     }
 
     public T decode(ConsumerRecord<String, byte[]> record) throws IOException {