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From Alan Conway <acon...@redhat.com>
Subject Re: CHANNEL_MAX and CHANNEL_HIGH_BIT question
Date Thu, 23 Jan 2014 21:27:30 GMT
On Thu, 2014-01-23 at 09:43 +0000, Gordon Sim wrote:
> On 01/22/2014 07:40 PM, Alan Conway wrote:
> > From qpid/cpp/src/qpid/framing/amqp_types.h:
> >
> > /** Maximum channel ID used by broker. Reserve high bit for internal
> > use.*/ const ChannelId CHANNEL_MAX=(ChannelId(~1))>>1; const
> > ChannelId CHANNEL_HIGH_BIT= ChannelId(~CHANNEL_MAX);
> >
> > Does anyone know if and where the channel high bit is used
> > internally? There's no reference to CHANNEL_HIGH_BIT anywhere in the
> > source.
> 
> It was introduced ages ago: 
> http://svn.apache.org/viewvc?view=revision&revision=551981. This is in 
> the 0-10 implementation, and I can't see anything in the 0-10 spec that 
> would require this. From the comment it sounds like it was maybe being 
> reserved in case it was needed 'internally' within the broker(?)
> 
> > This affects new HA which (currently) needs a channel per replicated
> > queue. The definition above limits us to 32k queues. Any thoughts on
> > the impact of changing this to 64k? For my purposes the change can be
> > server-side only, so the client could still limit channels to 32k (if
> > there's a reason to do that)
> 
> I can't see any reason for the limit, so I would be fine with changing it.

In that case I will go ahead and do it, reduce the odds of people
hitting the limit.



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