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Re: Draft spec for new dpkg "triggers" feature (v2, repost)

On Tue, Apr 10, 2007 at 07:27:06PM +0100, Ian Jackson wrote:
> When a trigger is activated, it becomes pending for every package
> which is interested in the trigger at that time.  Each package has a
> list of zero or more pending triggers.  Repeated activation of the
> same trigger has no additional effect.  Note that in general a trigger
> will not be processed immediately when it is activated; processing is
> deferred until it is convenient (as described below).
Will the idempotency be implemented by dpkg or by each interested
packaged?  That is, does dpkg keep track and simply not activate the
trigger subsequent times, or is it the responsibility of the maintainer
of the interested package to make sure that repeated activations don't
cause problems?

> When a package T activates a trigger in which an package I is
> interested, I is added to the list of packages whose trigger
> processing is awaited by T.  Zero or more packages I may be added as a
> result of any particular trigger activation, depending on how many
> packages were interested.
If the interested package fails to exit successfully from whatever it
does for its trigger, how is that treated?  Does dpkg continue and note
the error to the user?  I am thinking that you don't want such a failure
to prevent the triggerring package from finishing to install and

> The activation of a trigger does not record details of the activating
> event.  For example, file triggers do not inform the package of the
> filename.  In the future this might be added as an additional feature,
> but there are some problems with this.
I'd be interested to know in what problems there are with this.



Roberto C. Sánchez

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