Streams: Strange Throughput Variations with maxUnconfirmedMessages
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Peter Vaiko
Apr 12, 2025, 8:11:45 AMApr 12
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While testing the streams with 4.0.8 and Java client 0.24 I found some strange behavior.
I have a performance test where I publish 10,000 messages to a stream and measure the throughput (messages/second). The stream, the environment and the producer is recreated before each run.
The producer is all default, except with different maxUnconfirmedMessages setting at each run. I run the same test series, once with 64 bytes per message, once with 2048 bytes per message.
The broker is a single node, running on Kubernetes in Docker Desktop, I run my JUnit test natively on Windows from my IDE.
I expect the throughput to increase as I use bigger values for maxUnconfirmedMessages, and that is mostly the trend, however, there are some very strange outliers.
maxUnconfirmedMessages=10 seems always producing almost exactly 100 messages per second, while 9 or 11 is two orders of magnitudes higher, with both 64 and 2048 byte messages.
The 64 byte message throughput also shows a dip at maxUnconfirmedMessages=100 (but not at 99 or 101) and there are some weird variations around 1000, see below.
Can someone explain me what is going on here?
I have a performance test where I publish 10,000 messages to a stream and measure the throughput (messages/second). The stream, the environment and the producer is recreated before each run.
The producer is all default, except with different maxUnconfirmedMessages setting at each run. I run the same test series, once with 64 bytes per message, once with 2048 bytes per message.
The broker is a single node, running on Kubernetes in Docker Desktop, I run my JUnit test natively on Windows from my IDE.
I expect the throughput to increase as I use bigger values for maxUnconfirmedMessages, and that is mostly the trend, however, there are some very strange outliers.
maxUnconfirmedMessages=10 seems always producing almost exactly 100 messages per second, while 9 or 11 is two orders of magnitudes higher, with both 64 and 2048 byte messages.
The 64 byte message throughput also shows a dip at maxUnconfirmedMessages=100 (but not at 99 or 101) and there are some weird variations around 1000, see below.
Can someone explain me what is going on here?
Peter Vaiko
Apr 15, 2025, 6:38:31 AMApr 15
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Bump
Arnaud Cogoluègnes
May 12, 2025, 11:30:21 AMMay 12
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Following up on this, I published a fix [1], it will be available in stream Java client 1.1.0.
There was a problem when accumulating messages and releasing them for publishing, but only for some (edge) values of the maxUnconfirmedMessage producer setting.
Thanks for reporting this.
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