Hi Flink community, I have a question regarding the removal of several network buffer configuration options as described in FLIP-450:
* taskmanager.network.memory.buffers-per-channel * taskmanager.network.memory.floating-buffers-per-gate * taskmanager.network.memory.max-buffers-per-channel FLIP-450 notes that these options would be deprecated in 1.20 and removed in 2.0, based on the assumption that streaming jobs seldom configure them and that FLIP-266 sufficiently simplifies buffer management. However, we are running a high-throughput, shuffle-heavy streaming application where these settings were critical. On Flink 1.20, we explicitly tuned the network buffer counts to saturate downstream CPU. When the upstream was backpressured, the downstream operators were typically close to fully utilized. After upgrading to Flink 2.0, this behavior changed significantly. We now observe: * Upstream tasks being heavily backpressured. * Downstream tasks idling at ~10–20% busy ratio. * hardBackPressuredTimeMsPerSecond indicating mostly hard backpressure. * 0.Shuffle.Netty.Output.Buffers.inputQueueLength suggesting downstream does not receive enough data to process. This points to insufficient network buffering under the new model, and we are no longer able to compensate via configuration. Our TaskManagers run on several 100 Gbps machines, and on a typical day we utilize roughly half of the available network bandwidth, so this appears to be a real limitation for network-shuffle–bound workloads. Is there openness to reintroducing some form of tunability or alternative mechanism to better support such high-throughput jobs? I would be happy to help with a proposal or pull request if the community agrees this is a valid direction. Thanks for your time and feedback. Best regards, Han You ________________________________ The information in this e-mail is intended only for the person or entity to which it is addressed. It may contain confidential and /or privileged material, the disclosure of which is prohibited. Any unauthorized copying, disclosure or distribution of the information in this email outside your company is strictly forbidden. If you are not the intended recipient (or have received this email in error), please contact the sender immediately and permanently delete all copies of this email and any attachments from your computer system and destroy any hard copies. Although the information in this email has been compiled with great care, neither IMC nor any of its related entities shall accept any responsibility for any errors, omissions or other inaccuracies in this information or for the consequences thereof, nor shall it be bound in any way by the contents of this e-mail or its attachments. Messages and attachments are scanned for all known viruses. Always scan attachments before opening them.
