[Beowulf] Re: dealing with lots of sockets

Perry E. Metzger perry at piermont.com
Thu Jul 3 10:59:06 PDT 2008

Bogdan Costescu <Bogdan.Costescu at iwr.uni-heidelberg.de> writes:
> On Wed, 2 Jul 2008, Perry E. Metzger wrote:
>> Event driven programming typically uses registered callbacks that
>> are triggered by a central "Event Loop" when events happen. In such
>> a system, one never blocks for anything -- all activity is performed
>> in callbacks, and one simply returns from a callback if one can't
>> proceed further.
> And here is one of the problems that event driven programming can't
> really solve: separation between the central event loop and the code
> to run when events happen.

I don't understand what you mean.

> fork() allows the newly created process to proceed at its own will
> and possibly doing its own mistakes (like buffer overflows) in its
> own address space - the parent process is not affected in any way
> and this allows f.e. daemons to run their core loop with
> administrative priviledges while the real work can be done as a dumb
> user.

Oh, that's not an issue at all. For example, say you wanted to run an
SMTP daemon as a pure event app but you don't want it to run as
root. So, you're screwed because you can't open port 25 as a normal
user, right? Well, you can either change privs after opening 25, or
you can use fd passing to pass open file descriptors between a small
rootly process and the mail processing event driven process.

Anyway, yah, bugs are a problem. If you have a bug in an event driven
system you bring down 10,000 connections at once instead of 1. You
do indeed have to be confident your code doesn't suck.

Perry E. Metzger		perry at piermont.com

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