Re: number of contextcsn entries per database

[Howard Chu <hyc@symas.com>]

PJunod@mediageneral.com wrote:
> I have setup two ldap servers for authentication and access control in a
> multi-master configuration. I am concerned about the number of contextcsn
> entries that are supposed to be present in each database. Right now there are
> two servers participating in the multi-master configuration. From my
> understanding, there should be one contextCSN entry per database per host. My
> cn=config database has two contextCSN entries as I would expect. One for each
> syncrepl rid configured. My bdb database only has one contextCSN entry though,
> with an rid of just “000”. (my rid’s are 001, 002, 101, and 102)

ContextCSN is an attribute. Attributes have values, they do not have entries.

CSNs carry SIDs not RIDs.

If you don't use the correct terminology no one will understand what you're 
talking about.

If a database contains changes from more than one server, then its contextCSN 
should contain more than one value, and each value should have distinct SIDs. 
But the SIDs will only be used correctly if the URLs in the ServerID directive 
match the actual URLs given to the slapd -h option.

> Replication seems to work fine on both databases. I can write to either one
> and the changes are replicated over immediately. I am just curious about this
> discrepancy in the number of contextCSN entries. Could someone confirm the
> number of contextCSN entries per database and if it should match the number of
> hosts participating in the multi-master replication? Here are some relevant
> settings for the replication:
>
> dn: cn=config
>
> olcServerID: 1 ldap://<server1>
>
> olcServerID: 2 ldap://<server2>
>
> #######################
>
> # module{0}, config
>
> dn: cn=module{0},cn=config
>
> objectClass: olcModuleList
>
> cn: module{0}
>
> olcModulePath: /usr/lib64/openldap2.4
>
> olcModuleLoad: {0}syncprov.la
>
> #######################
>
> # {0}config, config
>
> dn: olcDatabase={0}config,cn=config
>
> olcSyncrepl: {0}rid=001 provider=ldap://<server1> binddn="cn=Ma
>
> nager,cn=config" bindmethod=simple credentials=<password> searchbase="cn=config
>
> " type=refreshAndPersist retry="5 500 5 +" timeout=1 starttls=yes
>
> olcSyncrepl: {1}rid=002 provider=ldap://<server2> binddn="cn=Ma
>
> nager,cn=config" bindmethod=simple credentials=<password> searchbase="cn=config
>
> " type=refreshAndPersist retry="5 500 5 +" timeout=1 starttls=yes
>
> olcMirrorMode: TRUE
>
> #######################
>
> # {0}syncprov, {0}config, config
>
> dn: olcOverlay={0}syncprov,olcDatabase={0}config,cn=config
>
> objectClass: olcOverlayConfig
>
> objectClass: olcSyncProvConfig
>
> olcOverlay: {0}syncprov
>
> #######################
>
> # {1}bdb, config
>
> dn: olcDatabase={1}bdb,cn=config
>
> olcSyncrepl: {0}rid=101 provider=ldap://<server1> binddn="cn=Ma
>
> nager,dc=mgcorp,dc=net" bindmethod=simple credentials=<password> searchbase="dc
>
> =mgcorp,dc=net" type=refreshAndPersist interval=00:00:00:10 retry="5 500 5 +"
>
> timeout=1 starttls=yes
>
> olcSyncrepl: {1}rid=102 provider=ldap://<server2> binddn="cn=Ma
>
> nager,dc=mgcorp,dc=net" bindmethod=simple credentials=<password> searchbase="dc
>
> =mgcorp,dc=net" type=refreshAndPersist interval=00:00:00:10 retry="5 500 5 +"
>
> timeout=1 starttls=yes
>
> olcMirrorMode: TRUE
>
> ##############################
>
> Here are the results of searches for contextCSN in cn=config and dc=mgcorp,dc=net:
>
> ldapsearch -x -W -s base -D "cn=Manager,cn=config" -h "<server2>" -b
> "cn=config" contextCSN
>
> contextCSN: 20101110214932.998233Z#000000#000#000000
>
> contextCSN: 20101028121213.444193Z#000000#001#000000
>
> ldapsearch -x -W -s base -D "cn=Manager,dc=mgcorp,dc=net" -h "<server2>" -b
> "dc=mgcorp,dc=net" contextCSN
>
> contextCSN: 20101110213409.736943Z#000000#000#000000


--
  -- Howard Chu
  CTO, Symas Corp.           http://www.symas.com
  Director, Highland Sun     http://highlandsun.com/hyc/
  Chief Architect, OpenLDAP  http://www.openldap.org/project/