Re: Sanity check: "Redirection URL" in "Load Balancing and Adaptor Settings"
Re: Sanity check: "Redirection URL" in "Load Balancing and Adaptor Settings"
- Subject: Re: Sanity check: "Redirection URL" in "Load Balancing and Adaptor Settings"
- From: Patrick Middleton <email@hidden>
- Date: Wed, 07 Nov 2012 09:52:32 +0000
Yes, that used to puzzle me.
How are you deploying? My deployments are seriously old-skool, 4.x-
style, with Apache and mod_WebObjects. mod_WebObjects can be
configured in three ways to know what applications and instances are
available (see the matching apache.conf). One is to poll the local
wotaskd over HTTP (default), another is to read an XML file, and the
third is to listen to multicast broadcasts from wotaskd running on
multiple hosts.
I've never used the multicast option but I expect it suffers from the
same problem the HTTP option does: no information is returned
describing applications for which there are no running instances; so,
if there are no running instances and you want the redirection URL,
the redirection URL is not available.
In my deployments I use the the XML file option. An easy way of
generating suitable XML is to wait until all instances are running
and do '/usr/bin/curl http://localhost:1085/WebObjects/wotaskd.woa/wa/
woconfig' . A good place to put such XML is /Library/WebObjects/
Configuration/WOConfig.xml , and you will need to edit
mod_WebObjects's apache.conf file.
Of course in the 5.4.x era everything could be completely different....
On 7 Nov 2012, at 07:37, Paul Hoadley wrote:
Hello,
I'm looking to implement a simple "downtime" page for an application
—if all instances are off, the user should see this page. For a
moment, I thought the "Redirection URL" in the application's
settings would handle this for me, but it doesn't seem to. The
semantics there seem to be quite specific, with "an instance fails
to respond to a direct request" entailing that there exists an
instance at all. Certainly, testing shows that "No instance
available" is returned instead of the redirection URL in the case
where there are zero instances running.
So how do people handle this? Looks like I would need to manually
create an Apache redirect/rewrite and bounce Apache, which seems
labour intensive.
--
Paul Hoadley
http://logicsquad.net/
---
Regards Patrick
OneStep Solutions (Research) LLP
www.onestep.co.uk
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