[GitHub] rdhabalia commented on a change in pull request #720: Position Reader on a specific message within a batch

[gi...@git.apache.org]

rdhabalia commented on a change in pull request #720: Position Reader on a specific message within a batch
URL: https://github.com/apache/incubator-pulsar/pull/720#discussion_r135885576
 
 

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 File path: pulsar-client/src/main/java/org/apache/pulsar/client/impl/ConsumerImpl.java
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 @@ -859,6 +865,21 @@ void receiveIndividualMessagesFromBatch(MessageMetadata msgMetadata, ByteBuf unc
                     .newBuilder();
                 ByteBuf singleMessagePayload = Commands.deSerializeSingleMessageInBatch(uncompressedPayload,
                     singleMessageMetadataBuilder, i, batchSize);
+
+                if (startMessageId != null
+                        && messageId.getLedgerId() == startMessageId.getLedgerId()
+                        && messageId.getEntryId() == startMessageId.getEntryId()
+                        && i <= startMessageId.getBatchIndex()) {
+                    // If we are receiving a batch message, we need to discard messages that were prior
+                    // to the startMessageId
 
 Review comment:
   just a quick suggestion if that make sense.
   1. what if we also add similar validation at `messageReceived()` for non-batch-msg also where we skip the message if `receivedMsgId < startMessageId`
   2. and at [broker ](https://github.com/merlimat/pulsar/blob/fa752f4f990c7cd604bee8fea3cc5aaf33bfe291/pulsar-broker/src/main/java/org/apache/pulsar/broker/service/persistent/PersistentTopic.java?utf8=%E2%9C%93#L477-L483) we always read from `entryId=entryId-1` and duplicate entry will be anyway skipped by the client.
   
   In this way, broker can be `BatchMessage` agnostic and it will not have any batch-msg specific logic as it treats  batch-msg as normal msg only.
 
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