[erlang-questions] On selective receive (Re: eep: multiple patterns)

Mats Cronqvist <>
Tue Jun 3 08:28:22 CEST 2008


Chandru wrote:
> 2008/6/2 Mats Cronqvist < 
> <mailto:>>:
>
>     Ulf Wiger wrote:
>     > I would really like to discourage people from avoiding
>     > selective receive because it's "expensive". It can be
>     > expensive on very large message queues, but this is
>     > a pretty rare error condition, and fairly easily observable.
>     >
>
>      i think the "issue" of how the emu deals with huge in-queues is
>     pretty
>     uninteresting.
>      in my personal experience, every single time this has come up the
>     real
>     problem has turned out to be lack of proper flow control (typically
>     using {active,true} sockets). having 100k messages in an in-queue
>     is not
>     a realistic use case.
>      the fact that this is not, afaik, particularly well documented is of
>     course a problem.
>
>
> This is true - but if one has no prior experience of this situation, 
> it is hard to understand why a system is behaving sluggishly. What 
> will be nice is having an option, as Ulf suggested earlier, to have 
> bounded message queues (kill the process if the message queue length 
> exceeds a certain value). That way, flow control problems will be more 
> readily visible to users. 

  true enough.

  mats



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