Re: olcServerID

[Pierangelo Masarati <ando@sys-net.it>]

Gavin Henry wrote:
> ----- "Pierangelo Masarati" <ando@sys-net.it> wrote:
>
> > andylockran wrote:
> > http://blog.suretecsystems.com/archives/40-OpenLDAP-Weekly-News-Issue-5.html
> > > In the third box of code, this appears to set up the Master node
> > with 3
> > > serverIDs +URLS, when previously it was set up with a single
> > serverID
> > > (which I assumed to be its identifier) is this correct?
> > The serverID config statement (olcServerID attribute in back-config)
> > is 
> > used to inform a specific server about its own id within a local 
> > replication pool.  Without URL, only one occurrence of serverID is 
> > allowed.  When the URL is specified, multiple occurrences are allowed,
> >
> > but only one takes effect: the one whose URL matches the listener of
> > the 
> > server.  So the URL-qualified multiple occurrences of serverID
> > basically 
> > allow to share the same configuration within multiple servers of the 
> > same replication pool, guaranteeing that each server will pick up the
> >
> > correct id based on the URL.
>
> Maybe this should be added to the replication section of the admin guide.
>
> The man page is consise:
>
>        serverID <integer> [<URL>]
>               Specify an integer ID from 0 to 4095 for this server (limited to 3 hexadecimal digits).  These  IDs  are  required
>               when  using multimaster replication and each master must have a unique ID. Note that this requirement also applies
>               to separate masters contributing to a glued set of databases.  If the URL  is  provided,  this  directive  may  be
>               specified  multiple  times,  providing a complete list of participating servers and their IDs. The fully qualified
>               hostname of each server should be used in the supplied URLs. The IDs are used in the "replica  id"  field  of  all
>               CSNs generated by the specified server. The default value is zero.  Example:
>
>             serverID 1

I think the man page is concise and precise.  The admin guide could 
benefit from some more detailed explanation, and some examples of the 
case with URI:

<slapd.conf>
	serverID 1 ldap://host1.example.com
	serverID 2 ldap://host2.example.com
	serverID 3 ldap://host3.example.com
</slapd.conf>

same slapd.conf, different FQDN:

host1.example.com takes ID 1
host2.example.com takes ID 2
host3.example.com takes ID 3

each DSA will generate entryCSNs like

host1.example.com: 20080830094621.123456Z#000000#001#000000
host2.example.com: 20080830094621.123456Z#000000#002#000000
host3.example.com: 20080830094621.123456Z#000000#003#000000

                                             SID ^^^

p.


Ing. Pierangelo Masarati
OpenLDAP Core Team

SysNet s.r.l.
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