[rabbitmq-discuss] Questions about limit alarm and report in the log file

[Matthew Sackman]

On Mon, Mar 12, 2012 at 04:33:50PM +0000, Rosa, Andrea (HP Cloud Services) wrote:
> >It is, however, a slightly imprecise measure. We can't control the use
> >of FDs by the Erlang VM itself, and some plugins don't make use of the
> >correct API to ensure we account correctly for FD usage.
> 
> When you said "imprecise measure", we are talking about a +-2% or +-20%?

Unknown. The Erlang kernal may use some descriptors itself. We have no
way of telling when it does or doesn't, so we arbitrarily reserve 100
for it and hope. Other plugins may or may not correctly register the use
of descriptors with Rabbit - for example, off hand, I've no idea whether
the management plugin registers its use of sockets with Rabbit
internally, likewise the STOMP plugin etc. It's probably safest to
assume they don't. Thus the internal accounting may be accurate or at
least conservatively accurate enough using plain vanilla Rabbit, but
might start to get a bit dodgy as you enable more plugins. Really those
plugins either need rewriting to use the necessary APIs (if they've not
already), or some other more robust mechanism needs to be invented.

Matthew