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Re: Replicating from a mirrormode pair to a read-only server

Hi Andrew,

On 10/09/2010 18:42, Andrew Findlay wrote:

On Fri, Sep 03, 2010 at 08:06:31PM +0200, Jonathan CLARKE wrote:


I don't have any problems using the 2 syncrepl statements side-by-side on
the slave. When one master goes offline, replication continues from the
other, etc.


I have done some more tests with a new slave machine having two
syncrepl clauses to talk to two mirrormode masters. This time I
pre-loaded the database from a recent LDIF backup and sync was achieved
in a few seconds. There were a few grumbles of the form:

Sep 10 17:05:41 nis2 slapd[6571]: conn=-1 op=0: attribute "mail" index delete failure
Sep 10 17:05:42 nis2 slapd[6571]: =>  bdb_idl_delete_key: c_get failed: DB_LOCK_DEADLOCK: Locker killed to resolve a deadlock (-30994)

I suppose these might lead to trouble later, but what is more worrying
is that I then ran slapcat backups of the two masters and the new
slave, and there is a difference. The two masters have identical data,
but...

The slave has one entry where pwdAccountLockedTime is missing. This
is an account that was locked by admin action between the initial load
data being dumped from the master server and the new slave being started
up, so it should have been replicated from one master or the other by
syncrepl. Every other attribute in the entry is identical, including the
modifyTimestamp which records when the pwdAccountLockedTime attribute
was added. I know that the entry did not change after that, as I have
a full changelog on both masters.
This is most likely a separate issue. Updates to the ppolicy operational attributes are not replicated like "standard" changes, but instead written directly into the local database. So it's to be expected that you see differences on these attributes between syncrepl consumers/providers.
See the ppolicy_forward_updates option in slapo-ppolicy(5) for details and a possible workaround. 

Jonathan

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