[Catalyst] Confused: how to handle system-level errors with fallback pages

Stuart Watt swatt at infobal.com
Mon Aug 30 20:12:38 GMT 2010

  I have a timing/configuration issue, and any pointers would be welcome.

The problem: how to handle configuration/system errors by fallback to an =

error page.

* I am using Catalyst authentication, but sometimes the database used =

for session storage cannot be connected. Under these circumstances, I =

want an error page which can be used to display an error suitable for a =

system administrator
* The application starts fine, because it does not attempt to connect =

* When a request starts, the session system fails during the prepare =

stage - calling stuff in Catalyst::Plugin::Session::Store::Delegate, and =

usually get_session_data
* The application never gets to finalize, so nothing is ever sent to the =

engine - this is the logic in handle_request

Where and how is it best to handle this?

I could do some of this before the first request, and I considered =

hacking which controllers were active since I can do that during the =

setup stage, but this is probably too late, since by then all the =

plugins are set up, and this is where the session management is set.

Alternatively, I could do some work during the request cycle, but it is =

not obvious where in the cycle you got to, which makes it hard to decide =

whether you can generate an error.

I could just be missing some documentation: maybe this is covered but I =

haven't been able to find it.

-- =

Stuart Watt
ARM Product Developer
Information Balance
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