[GitHub] [pulsar] merlimat commented on a change in pull request #6362: [ClientAPI]Fix hasMessageAvailable()

[GitBox <gi...@apache.org>]

merlimat commented on a change in pull request #6362: [ClientAPI]Fix hasMessageAvailable()
URL: https://github.com/apache/pulsar/pull/6362#discussion_r381502751
 
 

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 File path: pulsar-broker/src/main/java/org/apache/pulsar/broker/service/ServerCnx.java
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 @@ -1412,6 +1424,43 @@ protected void handleGetLastMessageId(CommandGetLastMessageId getLastMessageId)
         }
     }
 
+    private int getLargestBatchIndex(Topic topic, PositionImpl position, long requestId) {
+        PersistentTopic persistentTopic = (PersistentTopic) topic;
+        ManagedLedgerImpl ml = (ManagedLedgerImpl) persistentTopic.getManagedLedger();
+
+        CompletableFuture<Entry> entryFuture = new CompletableFuture<>();
+        ml.asyncReadEntry(position, new AsyncCallbacks.ReadEntryCallback() {
+            @Override
+            public void readEntryComplete(Entry entry, Object ctx) {
+                entryFuture.complete(entry);
+            }
+
+            @Override
+            public void readEntryFailed(ManagedLedgerException exception, Object ctx) {
+                entryFuture.completeExceptionally(exception);
+            }
+        }, null);
+
+        CompletableFuture<Integer> batchSizeFuture = entryFuture.thenApply(entry -> {
+            MessageMetadata metadata = Commands.parseMessageMetadata(entry.getDataBuffer());
+            int batchSize = metadata.getNumMessagesInBatch();
+            entry.release();
+            return batchSize;
+        });
+
+        try {
+            int batchSize =  batchSizeFuture.get();
 
 Review comment:
   This is being called within an IO thread. We cannot block on the future

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