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Re: Notifications

From: "Donald Fraser" <postgres(at)kiwi-fraser(dot)net>
To: "[ADMIN]" <pgsql-admin(at)postgresql(dot)org>
Subject: Re: Notifications
Date: 2004-12-16 17:44:09
Message-ID: 003701c4e396$d9b4a270$6464a8c0@DonAcer (view raw or flat)
Thread:
Lists: pgsql-admin
----- Original Message ----- 
From: "Michael Fuhr" <mike(at)fuhr(dot)org>
Sent: Thursday, December 16, 2004 5:07 PM
Subject: Re: [ADMIN] Notifications


> On Thu, Dec 16, 2004 at 02:20:07PM -0000, Donald Fraser wrote:
>
>> I'm having problems receiving NOTIFY messages when outside our local 
>> network.
>
> Define "problems."  What are you doing, what are you expecting to
> happen, and what actually does happen?  Have you tested whether you
> have the same problems when *inside* the local network?  The
> distinction between inside or outside may be a red herring.

Ok the problem is that outside our local network, and more precise on the 
outside of our firewall, users do not receive NOTIFY messages. The exact same 
software running on the local network, albeit not using SSL does receive NOTIFY 
messages.

>> I have dissabled firewall setting but nothing seems to fix the problem.
>
> What firewall setting did you disable and why?  Best not to mess
> around with things unless you have reason to think they'll work
> (in other words, avoid using a stab-in-the-dark approach).

I didn't change anything on our corporate firewall - it has tunnels through so 
that we can connect to the database, what I was disabling was the microsoft 
firewall on a PC connected to the database.

>> I was wandering if NOTIFY messages use UDP or TCP, as that would
>> possibly explain why they are not arriving?
>
> PostgreSQL's NOTIFY messages ride inside your connection to the
> database, so if you're connected across a network then they'll be
> TCP.  But you shouldn't have to do anything special to allow them:
> if you can connect to the database then you'll get notifications.
>
> A possible problem is that a firewall or other intermediate device
> times out idle connections.  Do you notice the problem after periods
> of no activity?

The problem is immediate, I can instanciate the sending of a NOTIFY message 
from my own connection and I don't receive a return message yet users on the 
local network do.

Basically now that I know NOTIFY uses TCP and therefore "should" clearly not be 
getting lost anywhere, I will do a lot more investigating into our software as 
that is the most likely place for the proble!. It just seems a bit strange that 
the same software can receive messages when on the local network... The one 
thing I can be sure of is that it will be software! I think the clue must be 
the setting up of SSL on our software....

Thanks for the input,
regards
Donald Fraser.

> -- 
> Michael Fuhr
> http://www.fuhr.org/~mfuhr/
> 


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