Re: [Firebird-devel] Timeout records - an idea for a feature

[Alex P. <pes...@ma...>]

 On 02/22/12 17:49, ik wrote:
> On Wed, Feb 22, 2012 at 13:34, Alex Peshkoff <pes...@ma...> wrote:
>>  On 02/22/12 00:14, ik wrote:
>>> Hello,
>>>
>>> For a long time now, I have an idea for a feature, that I gave it a
>>> name of "Timeout records"
>>> (http://idkn.wordpress.com/2012/02/20/timeout-records-feature-request/).
>>> Long before I'll ever try to report a feature request, I wish to have
>>> a discussion about it, to better understand things from the
>>> development point of view.
>>>
>>> The idea is to have a scheduler for records that on timeout can call a trigger.
>>> Many existed databases (such as Oracle, MS SQL Server and MySQL)
>>> contain a much wider idea, of task scheduler, while my idea is
>>> different.
>>> You can find more information on it at the post I linked above.
>>>
>>> I would really be interested in hearing the development side of
>>> things, and see how to develop the idea further before actually
>>> opening a bug report of a feature request.
>> Well, this has some problems.
>> - In what context should timeout trigger fire?
> I'm not sure that I understand this question.
>

Well, triggers typically work in context of user, attachment and
transaction which caused related data change in table. In what
attachment and with what user rights should your timeout triggers work?

>> - What to do if database server (or the whole box) is not active at the
>> moment when timeout should fire?
> Then there should be something like removing the record once it is up
> again and the TTL is over (garbage collection ?), and place on log of
> some sort by Firebird.
>
> Just an idea, like the whole subject :)
>

Well, it's possible.

>> For firebird that issues are even more funny.
>> - In what process should timeout trigger work in case of classic server?
> I do not know much about the internals of firebird, only on how to use
> it, so I do not know how to answer it.
>

If you use firebird, I suppose you should know that 2 server
architectures exist : classic server and super server. (In 2.5 there is
also superclassic, but let's leave it for a while). Superserver is
single process, serving all attachments. Classic server has dedicated
process per any attachment. So the question is - in which process (we
have NO kind of master process, all are same) should timeout triggers work?

>> - What to do if given database file is not opened when timeout should fire?
> I think that the answer is the same as the non responding issue.
>
>
> The reason I emailed it, was to understand things in the eyes of the
> database developers, so I could better understand things.
> Because as developers, we all know that it's very easy to request
> features, they are usually not that easy to implement.
>
> I think that at least task scheduler such as the databases I mentioned
> above have, can help a lot in this case, even if we do not have the
> "tmeout record" feature.

Well, please pay attention to the fact that using cron (or any other
external tool if cron does not satisfy your needs) to do that job solves
all mentioned problems automatically.