Encapsulating a notion of "message batch" in pub/sub

google-cloud-clients/google-cloud-pubsub/src/main/java/com/google/cloud/pubsub/v1/Publisher.java

@@ -84,8 +84,7 @@ public class Publisher {
   private final BatchingSettings batchingSettings;
 
   private final Lock messagesBatchLock;
-  private List<OutstandingPublish> messagesBatch;
-  private int batchedBytes;
+  private MessagesBatch messagesBatch;
 
   private final AtomicBoolean activeAlarm;
 
@@ -114,7 +113,7 @@ private Publisher(Builder builder) throws IOException {
     this.batchingSettings = builder.batchingSettings;
     this.messageTransform = builder.messageTransform;
 
-    messagesBatch = new LinkedList<>();
+    messagesBatch = new MessagesBatch();
     messagesBatchLock = new ReentrantLock();
     activeAlarm = new AtomicBoolean(false);
     executor = builder.executorProvider.getExecutor();
@@ -205,24 +204,19 @@ public ApiFuture<String> publish(PubsubMessage message) {
       // Check if the next message makes the current batch exceed the max batch byte size.
       if (!messagesBatch.isEmpty()
           && hasBatchingBytes()
-          && batchedBytes + messageSize >= getMaxBatchBytes()) {
-        batchToSend = new OutstandingBatch(messagesBatch, batchedBytes);
-        messagesBatch = new LinkedList<>();
-        batchedBytes = 0;
+          && messagesBatch.getBatchedBytes() + messageSize >= getMaxBatchBytes()) {
+        batchToSend = messagesBatch.popOutstandingBatch();
       }
 
       // Border case if the message to send is greater or equals to the max batch size then can't
       // be included in the current batch and instead sent immediately.
       if (!hasBatchingBytes() || messageSize < getMaxBatchBytes()) {
-        batchedBytes += messageSize;
-        messagesBatch.add(outstandingPublish);
+        messagesBatch.addMessage(outstandingPublish, messageSize);
 
         // If after adding the message we have reached the batch max messages then we have a batch
         // to send.
-        if (messagesBatch.size() == getBatchingSettings().getElementCountThreshold()) {
-          batchToSend = new OutstandingBatch(messagesBatch, batchedBytes);
-          messagesBatch = new LinkedList<>();
-          batchedBytes = 0;
+        if (messagesBatch.getMessagesCount() == getBatchingSettings().getElementCountThreshold()) {
+          batchToSend = messagesBatch.popOutstandingBatch();
         }
       }
       // Setup the next duration based delivery alarm if there are messages batched.
@@ -301,9 +295,7 @@ public void publishAllOutstanding() {
       if (messagesBatch.isEmpty()) {
         return;
       }
-      batchToSend = new OutstandingBatch(messagesBatch, batchedBytes);
-      messagesBatch = new LinkedList<>();
-      batchedBytes = 0;
+      batchToSend = messagesBatch.popOutstandingBatch();
     } finally {
       messagesBatchLock.unlock();
     }
@@ -637,4 +629,37 @@ public Publisher build() throws IOException {
       return new Publisher(this);
     }
   }
+
+  private static class MessagesBatch {
+    private List<OutstandingPublish> messages = new LinkedList<>();
+    private int batchedBytes;
+
+    private OutstandingBatch popOutstandingBatch() {
+      OutstandingBatch batch = new OutstandingBatch(messages, batchedBytes);
+      reset();
+      return batch;
+    }
+
+    private void reset() {
+      messages = new LinkedList<>();
+      batchedBytes = 0;
+    }
+
+    private boolean isEmpty() {
+      return messages.isEmpty();
+    }
+
+    private int getBatchedBytes() {
+      return batchedBytes;
+    }
+
+    private void addMessage(OutstandingPublish message, int messageSize) {
+      messages.add(message);
+      batchedBytes += messageSize;
+    }
+
+    private int getMessagesCount() {
+      return messages.size();
+    }
+  };
 }