Paul D wrote:

> Hi!
> Long time lurker, first time poster.
>
> I'm writing a web application that:
> "backend"
> Every three minutes parses a webpage and checks for problems (server
> monitoring). After that it matches those against a ruleset (SQLObject
> and pySQLite) to weed out unimportant problems.
>
> webui
> The web UI will reload a frame every 30 seconds to check for new
> problems and play an alarm there are any. The problem will be assigned
> to the user who first clicks on it, the user will either solve it and
> write down the solution, or create a new rule to ignore it in the future.
>
> Right now I got the "backend" kind of working. The problem is how to
> glue these parts together. I'm using medusa and I'd like to just one
> process - running the 'backend' as a thread. The server has to be able
> to run on winnt as a service. There won't be many users (max 15
> concurrent). Another thing is that the update/rulematching takes about
> 10-30 seconds and it's gonna be a mess if the webui checks for problems
> within an update, I'll need some kind of locking mechanism.
> I've come up with two solutions:
>

The NT service part shouldn't be a problem. Do you need sample code?


> 1. Start the backend as a thread in the quixote __init__py file. The
> webui will check a dictionary with problems in the backend every minute.
> Since I'm using medusa the thread will only be started once but it's not
> very pretty.
>

If you take this approach, read the recent postings on double-imports to be
sure you don't inadvertently start more than one thread!


> 2. Start the backend within the medusa_server.py script. I can't figure
> out a way to get the webui to have access to the backend namespace this
> way. Maybe subclass the Publisher and pass a reference to the backend in
> the request object?

Personally, I would prefer this over the implicit start-thread-on-module-import
approach. Subclassing Publisher.start_request() is easy and effective.

> Another solution is to make the backend write problems to a database
> table and have the webui check this table every minute.
>

You could also run the backend as a separate process/service, and have your Web
app talk to it via the database, or by some other protocol. Your backend and UI
services could share a common business-object package. If your backend may have
clients other than the Web app, this might be a sensible approach.


> Oh, another question: is it possible to raise an exception i the thread
> and have quixote exception tools handle it and present it when the user
> eventually fetches another page?
>

You could always store your exception reports in the database; then they are
just data, and the web UI could have a facet for viewing these repots.

> What's the best solution? I'm pretty new to python and designing bigger
> things then filename sorters so any input is interesting.
>
> thanks! / Paul

Best of luck!
-- Graham