# Consumer client and compacted topics

**URL:** <https://forum.confluent.io/t/consumer-client-and-compacted-topics/5536>\
**Category:** Clients\
**Created:** [14 July 2022 10:15 UTC](https://forum.confluent.io/t/consumer-client-and-compacted-topics/5536 "2022-07-14T10:15:53Z")\
**Posts on this page:** 1\
**Page:** 1

<div class="post-metadata">

**Author:** ![mm86](https://avatars.discourse-cdn.com/v4/letter/m/f14d63/32.png) [@mm86](https://forum.confluent.io/u/mm86)\
**Post date:** [14 July 2022 10:15 UTC](https://forum.confluent.io/t/consumer-client-and-compacted-topics/5536/1 "2022-07-14T10:15:53Z")

</div>

Hello,

I’m doing some tests on compacted topics and I noticed an unexpected behavior by the consumer. I created a compacted topic and a producer that generates hundreds of messages per second using 5 keys with random values.

After few seconds of message generation if I inspects the topic content with Offset Explorer I correctly see the compaction working (only the last values generated for each key are kept).

The problem appears with the following workflow:

1. The producer generates a bulk of messages on the compacted topic.
2. The consumer connects to the cluster, it subscribes to the compacted topic and after a first poll action it correctly receives only the most recent values for each key.
3. The consumer remains connected and subscribed but it waits for a user interaction before performing the next poll action.
4. The producer generates an other bulk of messages.
5. Using Offset Explorer I see that even with this second message generation the compaction has been successfully executed.
6. The consumer performs a second poll and now it receives **all** the messages generated in the last bulk, not only those kept by the compaction process.

I tried to write different consumer and producer clients (in C# and C++) and I played with configuration parameters for both the consumer and the compacted topic but **it seems that the only way for a consumer to receive only the compacted messages is to reconnect to the cluster or to change the group id**. Otherwise the connected consumer receives always all the messages produced.

Is this the expected behavior? Because I cannot figure out what I’m doing wrong.

Thanks