many "Connection closed" messages after receiving the warning "Received send error from the server: Cannot determine whether the message is a duplicate at this time" from producer

[TalkWIthKeyboard]

In my program, there will be eight producers, two of which will be sent to partitioned topics and six of which will be sent to unpartitioned topics.

Below is my topic configuration:

producer = client.create_producer(  
    producer_name='raw-test',  
    batching_enabled=True,  
    block_if_queue_full=True,  
    batching_type=BatchingType.KeyBased,  
    batching_max_messages=2000,  
    batching_max_allowed_size_in_bytes=1000 * 1024,  
    batching_max_publish_delay_ms=20,  
    compression_type=pulsar.CompressionType.ZSTD,  
    send_timeout_millis=0,  
    topic='persistent://ethereum-test/raw/tests'  
)

I am using sendAsync() to send messages, but I am getting many "Connection closed" messages after receiving the warning "Received send error from the server: Cannot determine whether the message is a duplicate at this time".

I also found that I can remove BatchingType.KeyBased or turn off batching-mode without encountering this problem, and that the problem does not consistently occur.

Here are my debug logs:
pulsar_log.txt

pulsar-client version is 2.10.1
pulsar cluster version is 2.10.2

[BewareMyPower]

There was a fix at the Java client: apache/pulsar#15413. Maybe we need to include this fix at the upstream C++ client as well.

It seems that you have enabled the deduplication at the broker side? The key based batching still doesn't work perfectly with message deduplication.

[TalkWIthKeyboard]

There was a fix at the Java client: apache/pulsar#15413. Maybe we need to include this fix at the upstream C++ client as well.

It seems that you have enabled the deduplication at the broker side? The key based batching still doesn't work perfectly with message deduplication.

Txs, so if I need key based batching work with message deduplication, I should use java client now only?

[BewareMyPower]

Yes. But as I've said before:

The key based batching still doesn't work perfectly with message deduplication.

Take the example in apache/pulsar#15413 (comment), assuming there are 4 messages that were grouped into two batches:

• A: 0, 3 (i.e. messages whose keys are all "A", and the sequence ids are 0 and 3)
• B: 1, 2

After batch B is persisted, the sequence id will be updated to 2 at the broker side. If batch A failed to be sent and the producer resent batch A, msg-0 will be rejected and then message lost would happen.

[TalkWIthKeyboard]

Yes. But as I've said before:

The key based batching still doesn't work perfectly with message deduplication.

Take the example in apache/pulsar#15413 (comment), assuming there are 4 messages that were grouped into two batches:

• A: 0, 3 (i.e. messages whose keys are all "A", and the sequence ids are 0 and 3)
• B: 1, 2

After batch B is persisted, the sequence id will be updated to 2 at the broker side. If batch A failed to be sent and the producer resent batch A, msg-0 will be rejected and then message lost would happen.

Thanks, I got it. Does pulsar have a plan to implement a more powerful de-duplicate mechanism? It sounds like a bug or big limit for de-duplicate mechanism now.

[BewareMyPower]

AFAIK not. The limitation is from the key based batching. When it was introduced, the deduplication case was not considered well.