Re: [PATCH] Implement persistent id for proxies and servers

Hi Krzysztof,

On Fri, Feb 29, 2008 at 12:19:20PM +0100, Krzysztof Oledzki wrote:
>
>
> On Thu, 28 Feb 2008, Willy Tarreau wrote:
>
> >On Sat, Feb 23, 2008 at 01:22:41AM +0100, Krzysztof Oledzki wrote:
> >>>From be4c911d87a6ac800a1fb33828fa87b5fc2806a6 Mon Sep 17 00:00:00 2001
> >>From: Krzysztof Piotr Oledzki <ole#ans.pl>
> >>Date: Sat, 23 Feb 2008 01:19:10 +0100
> >>Subject: [PATCH] [MINOR] Implement persistent id for proxies and servers
> >>
> >>This patch adds a possibility to set a persistent id for a proxy/server.
> >>Now, even if some proxies/servers are inserted/deleted/moved, iids and
> >>sids can be still used reliable.
> >
> >I like the idea a lot. I have merged your patch (with a few minor typos
> >such as BACKED->BACKEND, or CVS->CSV).
>
> Right, sorry. :(
>
> >Right now, I'm a bit worried about the requirement to assign ids > 1000
> >and the fact that we don't check for conflicts (I know people with almost
> >500 instances).
>
> Hm. I assumed that 1000 should be fine as no one is supposed to have so
> many proxies.

you know the difference between what people are supposed to do and what you encounter in production :-)

> Obviously I was mistaken. We can bump this number (10K?) or
> write a documentation warning that with *really* big installations custom
> IDs should start with 10K. Of course checking for conflicts is still
> necessary, however it is better if they do not occur. ;)

yes, and if we check for conflicts, then we should be able to skip fixed numbers in automatic numbering. Let's say that a first version requires high values and that a later one will be able to automatically assign values avoiding conflicts.

> >But we'll be able to improve this later. I have already identified that
> >proxies should be dual-linked. It will then be easier to move instances
> >in the list, then automatically assign numbers to the unnumberred ones.
>
> Currently IDs are assigned to all instances and then overrried by a
> peristant ID. I did it intentionally not to mix up IDs of other instances
> if some get a persistent one.

I think this is an excellent idea.

Now I see how we would proceed to correctly assign the IDs :

• first pass: config is parsed, and automatic consecutive IDs are assigned to all proxies. Those which have a fixed ID store this ID in a table (well, tree for speed). If the entry already exists => conflict.
• second pass: the list of proxies is scanned. Automatically assigned IDs are looked up in the tree to see if they are already assigned. If they are, then the next unused value is used, and the next value is used as the min for ongoing checks.

best regards,
willy Received on 2008/03/04 06:04