Re: [PATCH] implement "track backend/server"

On Sun, 10 Feb 2008, Willy Tarreau wrote:

> On Tue, Feb 05, 2008 at 09:37:06PM +0100, Krzysztof Oledzki wrote:
>>> From 75107d3319f77f4fcf7f5cfe8174046aca1766cf Mon Sep 17 00:00:00 2001
>> From: Krzysztof Piotr Oledzki <ole#ans.pl>
>> Date: Tue, 5 Feb 2008 21:29:31 +0100
>> Subject: [RFC] implement "track backend/server"
>>
>> This rfc-quality patch implements ability to set a current state of
>> one server by tracking another one. It:
>
> Wow, that's an excellent news!
>
> BTW, I think that it is a good thing to use a notifier list, because it
> will make it easier to later track scripts. That's what I did in keepalived
> IIRC.
>
> Just a few comments :
> - when you parse the "track" keyword, I think that the name of the proxy
> and server should not be checked immediately, but deffered. This would
> allow to track independently of the declaration order. That's what is
> done for use_backend for instance. The change is not necessarily hard,
> it basically consists in moving the assignment code further (around
> line 3000 in cfg_parse.c), and adding a check to ensure that
> srv->tracked->tracked == NULL to ensure there's no loop and that we're
> not chaining tracking.

Fine. I'll do it.

> - there's one extra comma in the chunk below :

Opps, sorry and thank you for finding it.

> Other than that, the code looks good.

OK, I'll send a corrected version ASAP with additional comments in the code and the documentation.

> Do you think that it would be useful to implement a more generic notifier
> mechanism now or should we delay it when we implement scripted checks ?
>
> The idea would be to separate servers and checks, with checks affecting server
> states by propagating the change along a list, and doing so for themselves
> too, so that the code remains as generic as possible. This way, simple checks
> and complex scripts would simply consist in normal tasks notifying a server
> list about state changes.

Yes, I have also thought about it, but found it little to more time consuming to do it now. I think it would be better to implement it together with scripted checks.

Best regards,

                         Krzysztof Oledzki Received on 2008/02/10 14:23