Re: compare uidNumber in LDAP

[John Ziniti <jziniti@speakeasy.org>]

You don't need the additional lock record.  The delete & add
operation serves as your lock record.  If your delete & add
succeeds, then you got the correct uidNumber.  If it fails,
you missed the boat and you have to *re-read* the uidNumber
and try again!

No race condition.

Yary Hluchan wrote:
> Delete and add still has a race condition.  While delete & add is atomic,
> reading the old uidNumber isn't part of that.  Example-
>
> Process A reads uidNumber 500
> Process B reads uidNumber 500
> Process A deletes & adds uidNumber 501 before B continues
> Process B deletes & adds uidNumber 501
>
> So now you have two identical uids.
>
> Answer:
> Create a lock record (such as dn: cn=maxUidLock,dc=example,dc=com)
> Read uidNumber record
> Modify uidNumber record
> Delete lock record
>
> If you cannot create a lock record, then wait and retry.
>
> -y
>
> ~~~~~
> The Moon is Waning Gibbous (84% of Full)