zhijiang created FLINK-7282:
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Summary: Credit-based Network Flow Control
Key: FLINK-7282
URL: https://issues.apache.org/jira/browse/FLINK-7282
Project: Flink
Issue Type: New Feature
Components: Network
Reporter: zhijiang
This is a part of work for network stack improvements proposed in
[~StephanEwen] 's
[FLIP|https://docs.google.com/document/d/1chTOuOqe0sBsjldA_r-wXYeSIhU2zRGpUaTaik7QZ84/edit#]
Backpressure currently happens very naturally through the TCP network
connections and the bounded buffering capacity. The downsides are :
* All channels multiplexed into the same TCP connection stall together, as soon
as one channel has backpressure.
* Under backpressure, connections can not transport checkpoint barriers.
This flink-managed flow control is similar with the window-based advertisement
mechanism in TCP. The basic approaches are the following:
* Each RemoteInputChannel has fixed exclusive buffers as initial credits, and
the SingleInputGate has a fixed buffer pool for managing floating buffers for
all RemoteInputChannels.
* RemoteInputChannel as receiver notifies the current available credits to the
sender side.
* Senders must never send buffers without credit, that means all the buffers
sent must be accepted by receivers and no buffers accumulated on the network
wire.
* Senders also sends the current size of backlog that indicates how many
buffers are available on the sender side. The receivers use this information to
decide how to request floating buffers from the fixed buffer pool.
To avoid immediate commits affecting master branch, it will be implemented into
a separate feature branch.
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