Re: posix message queues and multiple receivers

[Mouse <mouse%Rodents-Montreal.ORG@localhost>]

>> Why do you think it is meant to connect only two processes?  It is
>> [...] just a FIFO queue of messages.  [...]
> So what is the purpose of those interface?  When I inject a message,
> I don't know which of the possibly many receivers is getting it?

Right.  To rephrase that, "when I make a request, I don't know which
worker process will service it".  But you also don't _care_ which.

Consider nfsd: it typically has multiple worker processes (four by
default); when a client sends a request, it doesn't know which worker
will handle it, nor does it care.  (It typically uses sockets, but they
are the same in this respect: each message goes to exactly one reader,
no matter how mnay readers are reading.)

> I somewhat fail to understand the utility of more than one receivers.

When serving a request takes nontrivial time, and multiple requests can
usefully be in progress at once, it is useful - it typically improves
performance - to have multiple workers serving requests.  NFS, as
mentioned above, is a fairly good example (in these respects).

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