On 17/08/16 23:43, Steve Morin wrote:
Twisted Community
Problem: How do you determine the buffer size of a transport, to know
how much data is waiting to be transmitted from using transport.write?
You haven't received many responses, so I'll add a short note here:
The ideal way to do this IMO is to have the receiver send
acknowledgements with a sequence number to the sender once a message has
been received *and processed*. Keep track of these at the sender and
adjust the sending rate accordingly.
Another complementary approach is for the client to keep track of the
length (in space or in time/age) of it's local
received-but-not-processed queue and report this. Keeping track of the
queue in terms of delay is close to the CoDel approach for AQM.
Depending on the network portion of the implementation, the mere fact of
a message having been received and TCP-ack'd doesn't tell you the client
is keeping up - it might be receiving and buffering into RAM and getting
more and more backlogged.
If you can't alter the protocol to include protocol-level ack messages
then obviously you have to go the less satisfactory route and estimate
it from the lower-layer transport. As JP has noted, you can get this
from the kernel.
Flow control is hard ;o)
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