Hi, I'm checking Key_Shared feature and faced some unexpected behavior. What happened roughly is, multiple messages with the same key go to different consumers (consumer threads) even though Key_Shared is set. Also, the distribution of messages to consumers is quite skewed.
Let me explain what I did, what happened, and what was my expectation in more detail. What I did: 1. Created a partitioned topic named "persistent://my-tenant/my-namespace/my-topic8" (# of partitions is 8) 2. Ran a producer (the code is here. https://github.com/feeblefakie/misc/blob/master/pulsar/src/main/java/MyProducer.java ) - it just produces 10000 messages with SinglePartition. each message has a key (from "0" to "999") 3. Ran a consumer process (the code is here. https://github.com/feeblefakie/misc/blob/master/pulsar/src/main/java/MyConsumer.java ) - It consumes messages with Key_Shared and 20 consumer threads set by ClientBuilder.listenerThreads(20). What happened: Multiple messages with the same key go to different consumer threads. For example, the following is a set of messages with key "100" but some goes to b4fa8 others go to 96ee9. #ConsumerName key b4fa8 100 b4fa8 100 b4fa8 100 b4fa8 100 96ee9 100 96ee9 100 96ee9 100 96ee9 100 96ee9 100 96ee9 100 Also, distribution of messages are pretty skewed. # numOfMessages consumerName 289 15588 346 21dcb 138 284ca 379 29138 195 30276 533 500ae 375 5c4cb 338 654bf 194 699fe 271 6c6c8 220 73691 152 7f5d1 372 96ee9 359 9b55d 315 a22fd 196 a752a 4243 b4fa8 <- this consumes most of the messages 387 cc11a 307 d0f5d 391 ec8b8 What I expected: First, multiple messages with the same key go to the same consumer thread as described in below. http://pulsar.apache.org/docs/en/concepts-messaging/#key_shared Second, messages are almost equally balanced between consumer threads. So, am I doing something wrong ? or my expectation is wrong ? If my expectation is correct, It would be great if anyone can teach me how to make it happen. Best regards, Hiroyuki