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Re: [Fedora-directory-users] Questions about setting up replication by modifying ldap directly.

Ryan Braun wrote:
On Tuesday 11 December 2007 8:31 pm, Rich Megginson wrote:
Ryan Braun wrote:
I'm working on a perl script that will allow you to setup replication
agreements from the commandline using Net::LDAP.  I've pretty much taken
most of the ideas out of the existing mmr.pl and added some more
functionality ( and made the code look alot worse lol :)
It's perl - how could it possibly look any worse than it already is :P

Can you make your perl script available to the community?

I'll provide it on one condition, no on makes fun of me :) I'll probably have something rough tomorrow or thursday,

I have a couple questions about a few attributes involved in the various
object classes used in replication,  and a couple logic questions to

First off,  I've been using the sun docs from 6.1 here


for some of the attribute and object class info.  I hope it still applies
Looks like it mostly still applies.  Use this as your primary reference
- http://www.redhat.com/docs/manuals/dir-server/pdf/ds71cli.pdf and see

Will do.

1.  When using the console,  and you right click the replication
agreement,  you have the option to "Send Updates Now".  Which attribute
does that set?  I'm assuming its not nsds5BeginReplicaRefresh,  but that
looks like the closest item from either nsDS5Replica or
nsDS5ReplicationAgreement object classes.
It probably uses the "trick" of setting the replication schedule to some
bogus value (e.g. "0 0000-0001") then setting it back to its original
setting.  This will in effect tell replication to send all updates
immediately.  nsds5BeginReplicaRefresh is only used for full replica

The reason I ask, is when I was playing around and turned off one of the consumer servers, it came back and was taking a while so sync up the updates from the supplier. I wasn't sure what kind of time frame to expect in this situation. That and it seems like a handy option.
The supplier will by default attempt to send updates immediately. If the consumer goes down, the supplier will keep trying to reach it, using an exponential backoff strategy, until it attempts to contact the consumer every 5 minutes. So at most you should only have to wait 5 minutes after the consumer comes back online.
Now for some logic questions.  When creating a Supplier -> dedicated
consumer replication.  Here's a rough outline of what I'm doing

1.  Supplier -> create replication user
Unless the Supplier will also be a Consumer, this step is not necessary.

Ahh ok, I'll assume that all suppliers will be setup as MMR for now. Maybe add SMR functionality later if needed.
2. Consumer -> create replication user
3. Supplier -> add changelog object ("cn=changelog5,cn=config")
4. Consumer -> add changelog object ("cn=changelog5,cn=config")
Unless the Consumer will also be a Supplier, this step is not necessary.

ok so read only consumers don't need the changelog object.
5. Supplier -> add replica object
("cn=replica,cn=\"$config{BASE_DN}\",cn=mapping tree,cn=config") 6.
Consumer -> add replica object
("cn=replica,cn=\"$config{BASE_DN}\",cn=mapping tree,cn=config")
(consumer and supplier rep objects do have their own specific settings in
these objects) 7. Supplier -> create rep agreement object
("cn=\"Replication to $to\",cn=replica,cn=\"$base\",cn=mapping
tree,cn=config") 8.  Consumer -> update referral information in
dn: cn=$config{BASE_DN},cn=mapping tree,cn=config (nsslapd-referral
attribute) and
dn: cn=replica,cn="$config{BASE_DN}",cn=mapping tree,cn=config
(nsDS5ReplicaReferral attribute)
This should not be necessary unless you want to provide custom
referrals.  The server will automatically set the referrals back to the
Supplier or Master.

I wasn't sure if these entries were populated dynamically or if they needed to be manually set. Here's a question I forgot to ask before. Say you have 2 or 3 or X amount of suppliers feeding a read only consumer. Will the consumer automatically figure out it can send referrals back all the servers. ie. the first server on the referral list is down so send to the second. Is there some replication protocol magic going on that lets the consumers know what the referrals should be and then auto populates the nsDS5ReplicaReferral and nsslapd-referral attributes?
The referrals are automatically set to go to all of the masters, but there is no guaranteed order. So there is no guarantee of which master the client will be referred to, only that it will be referred to one of the masters.
9. Consumer -> modify dn: cn=$config{BASE_DN},cn=mapping tree,cn=config
attribute nsslapd-state to "referral on update"
I think this is also unnecessary, but should be ok anyway.

I *think* thats it.  From what I can when dumping cn=config the 3 objects
on the consumer end up something like this.  Also there's an empty value
for nsslapd-referralmode:  is that normal?
I think so.

# dc\3Dxxx\2Cdc\3Dec\2Cdc\3Dgc\2Cdc\3Dca, mapping tree, config
dn: cn="dc=xxx,dc=ec,dc=gc,dc=ca",cn=mapping tree,cn=config
objectClass: top
objectClass: extensibleObject
objectClass: nsMappingTree
cn: "dc=xxx,dc=ec,dc=gc,dc=ca"
nsslapd-state: referral on update
nsslapd-backend: userRoot
nsslapd-referral: ldap://SRVR1:389/dc=xxx,dc=ec,dc=gc,dc=ca
nsslapd-referral: ldap://SRVR2:389/dc=xxx,dc=ec,dc=gc,dc=ca

# replica, dc\3Dxxx\2Cdc\3Dec\2Cdc\3Dgc\2Cdc\3Dca, mapping tree, config
dn: cn=replica,cn="dc=xxx,dc=ec,dc=gc,dc=ca",cn=mapping tree,cn=config
objectClass: nsDS5Replica
objectClass: top
nsDS5ReplicaRoot: dc=xxx,dc=ec,dc=gc,dc=ca
nsDS5ReplicaType: 2
nsDS5Flags: 0
nsds5ReplicaPurgeDelay: 604800
nsDS5ReplicaBindDN: uid=RManager,cn=config
cn: replica
nsDS5ReplicaId: 65535
nsDS5ReplicaName: 60c64002-1dd211b2-8039bd5e-680e0000
nsDS5ReplicaReferral: ldap://SRVR1:389/dc=xxx,dc=ec,dc=gc,dc=ca
nsDS5ReplicaReferral: ldap://SRVR2:389/dc=xxx,dc=ec,dc=gc,dc=ca
nsds5ReplicaChangeCount: 2
nsds5replicareapactive: 0

# changelog5, config
dn: cn=changelog5,cn=config
objectClass: top
objectClass: extensibleObject
cn: changelog5
nsslapd-changelogdir: /opt/fedora-ds/slapd-srvr3/changelogdb

Now for setting up an MMR agreement between 2 suppliers

1. Source -> create rep user
2. Target -> create rep user
3. Source -> create changelog object
4. Target -> create changelog object
5. Source -> create replica object
6. Target -> create replica object
7. Source -> create rep agreement
8. Target -> create rep agreement
9. Source -> set nsDS5BeginReplicaRefresh in the rep agreement on the
source to init the target. 10. Source -> update dn:
cn="$config{BASE_DN}",cn=mapping tree,cn=config attribute
nsslapd-referral with the ldap://target:PORT/$config{BASE_DN} 11. Target
-> update dn: cn="$config{BASE_DN}",cn=mapping tree,cn=config attribute
nsslapd-referral with the ldap://source:PORT/$config{BASE_DN}
10, 11 - the referrals should be set automatically.

How does that look?
Looks good.

Should the multi-valued attribute nsslapd-referral contain entries for
each server for which it has a MMR agreement with?
Yes, but that should be handled automatically, unless you want to
override it.

Same replication protocol magic question as above.

Ryan Braun
Informatics Operations
Aviation and Defence Services Division
Chief Information Officer Branch, Environment Canada
CIV: (204) 833-2500x2824 CSN: 257-2824  FAX: (204) 833-2524
E-Mail: Ryan Braun ec gc ca

One other question,  it seems that sometimes the value has the escape
codes for the comma while sometimes it has the actual comma.

ryan infinity:~/fds-tools$ grep -i Referral *

I assume either way will work and not break anything?  (which seems to be
the case as it's running :)

Ryan Braun
Informatics Operations
Aviation and Defence Services Division
Chief Information Officer Branch, Environment Canada
CIV: (204) 833-2500x2824 CSN: 257-2824  FAX: (204) 833-2524
E-Mail: Ryan Braun ec gc ca

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