Efficient way to read data from a socket while calculating instant bitrate

Sebastien Merle <>
Thu Jul 30 13:17:23 CEST 2009


Hi,

I am reading data from a socket, and I want to be able to calculate
the instant bitrate over a period of time.

I am currently doing something like:

download(Sock, Monitor) ->
    erlang:send_after(?MONITORING_PERIOD, self(), {monitor}),
    download(Sock, Monitor, erlang:now(), 0).

download(Sock, Monitor, LastTime, BytesDelta) ->
    ok = inet:setopts(Sock, [{active, once}]),
    receive
        {tcp, Sock, Data} ->
            download(Sock, Monitor, LastTime, BytesDelta + size(Data));

        {tcp_closed, Sock} -> ok;

        {monitor} ->
            Now = erlang:now(),
            TimeDelta = timer:now_diff(Now, LastTime),
            Rate = (BytesDelta * 1000000) div TimeDelta,

            Monitor ! {rate, self(), Rate},

            erlang:send_after(?MONITORING_PERIOD, self(), {monitor}),
            download(Sock, Monitor, Now, 0)
    end.

This is working, but with very high bitrates it seems rather inefficient because
it receives a lot of small messages.

It request the packets one by one by calling inet:setopts because it does
some client-side rate control at the same time (not included in the
sample code).

Any suggestions to make this more efficient ?


Regards,
Sebastien Merle.


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