[Freeipa-devel] automount in LDAP

[Simo Sorce]

On Fri, 2008-11-07 at 12:07 -0500, Dmitri Pal wrote:
> >
> > If we add some sort of location identifier for automount what 
> > implications does this have for other features? Do we want to have 
> > per-location settings for anything else?
> >
> > My plan is to embed the location into the DN of the automount map and 
> > key names using cn.
> >
> > For the UI we'll need some method of selecting/managing this list of 
> > locations (drop-down box comes to mind). I'm not sure if storing this 
> > separately is a good idea or not.
> >
> > I just want to avoid any short-term choices I make don't have 
> > long-term consequences.
> >
> 
> Yes I agree . We need to have a more generic approach to that.
> 
> I am struggling with understanding how client would determine which 
> location he is in.
> I do not think that it should be based on the server the client is 
> connected to.
> This approach would require servers to serve out data different from 
> data being served by other replica. But what if the client fails over? 
> Does not seem like a good approach  imo.
> So may be using IP address range  would be a better indication?
> May be we have a part of client policy that would say :
> 
> Location A: range1, ragne2, range 3
> Location B: range4, ragne5, range 6
>  
> This approach works if you can determine the right IP to check. From my 
> past experience answering the question "which of my IPs is the IP that 
> server sees" is not a trivial answer.
> But let us say we dealt with that. Then as soon as client gets online it 
> would know its IP so it will know its location so it will be able to 
> construct a search filter and add it to the search string.

It is not a simple task, that said I have been working on a document on
DNS based location discovery for some time, I will try to publish it as
soon as I have some time.

> I really like the idea of having location as an attribute. Then for any 
> object that client needs to fetch and it can be location specific it 
> would just add to the search filter:
> ( | (location=<determined location>) (!(location))) This will pull down 
> all entries that are specific to the location or entries that are not 
> location specific.
> 
> This logic can be then reused across different entities not only mounts.

It is fundamental for SSSD to be able to discover the closest IPA
service and fallback to the next closest in case of problems and so on.
It's a fundamental feature we have been discussing for some time months
ago, I will publish some docs as soon as possible.

Simo.

-- 
Simo Sorce * Red Hat, Inc * New York