[Mailman-Developers] GSOC:Populating two default styles

[Barry Warsaw]

On Jun 24, 2016, at 03:14 AM, Harshit Bansal wrote:

>I was trying to populate the two default styles in the database. For
>this purpose, I was trying to use ConfigurationUpdatedEvent as used in
>the earlier style manager but I am recieving following error:
[...]
>AttributeError: No section or category named db.
>
>It seems that the database layer hasn't got initialized by the time
>this event was fired. Is there any way of fixing this or any other way
>using which I can populate the database when mailman starts?

That's right.

Getting the initialization sequence correct is pretty tricky, and it's true
that the configuration subsystem is initialized before the database connection
is created.  If you think about it, it has to be this way since there are
settings in the config files that control how the database is set up.

What I think this means for you is that you can't use the
ConfigurationUpdatedEvent to set up your stylets until the database is set
up.  Unfortunately, right now there aren't any events fired when
initialization is completely, but just the other day Aurelien and I sketched
out an event-based plugin mechanism for better HK integration, and one of the
things I realized we needed was some additional event notification for the
various stages of initialization.

Right now, your best hope is to use the [mailman]post_hook which gets run
during initialize_3() and is guaranteed to be run after both the configuration
subsystem and the database connection is set up.  Eventually the pre_hook and
post_hook will be deprecated because they aren't really set up well for
plugins, and we'll have events for the various phases of initialization, so
you could register a handler for one of those events.

If you decide to keep the ConfigurationUpdatedEvent handler (e.g. because you
want to do other stylet things if the configuration changes once the system is
up and running), just check for the existence of the config.db attribute, or
catch the AttributeError.  If the attribute is missing, you know the
ConfigurationUpdatedEvent is too early for your purposes.

Hope that helps.
-Barry