[erlang-questions] Sender punishment removed

[Jesper Louis Andersen]

call(Msg) ->
    gen_server:call({Msg, erlang:monotonic_time()}).

receive
    {Msg, In} ->
      Out = erlang:monotonic_time(),
      Sojourn = erlang:convert_time_unit(Out - In, native, milli_seconds),
      case Sojourn > 5000 of
          true -> {reply, argh, State}
          false -> ...
       end
end

is usually a better way of tracking calls if you have overflow troubles.
Sojourn tracking and head-drop from the FIFO is what CoDel does, and it
works wonders on network connections. It can avoid having to process
messages in the queue which already fell for a timeout. Better, you can do
case (Sojourn + ExpectedProcessingTime) > ?LIMIT of ..., which can avoid
doing work which will break the time limit anyway, proactively.



On Tue, Jan 23, 2018 at 12:35 PM Guilherme Andrade <g@REDACTED> wrote:

> On 23 January 2018 at 10:30, Max Lapshin <max.lapshin@REDACTED> wrote:
>
>> 1) client comes to HTTP
>> 2) http handler makes gen_server:call to singleton server
>> 3) waits for 5 or 60 seconds and then exits, but message is already in
>> process queue
>> 4) server fetches this useless message from mailbox and starts making
>> useless expensive operations
>> 5) meanwhile client makes another duplicate request and again fills
>> singleton mailbox with the same request
>>
>
> I've recently started to explore sbroker[1] as an alternative (in some
> cases) and I've been getting very interesting results.
>
> Then again it's also (IIRC) backed by single processes that might become a
> bottleneck themselves, but at least those processes aren't doing anything
> else. Also, because it's this big toolkit with a lot of bells and whistles,
> it's easy to shoot yourself in the foot if you're not already acquainted
> with some of the abstractions, and so there might be somewhat of a learning
> curve.
>
> [1]: https://github.com/fishcakez/sbroker
>
> --
> Guilherme
>
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