[Phpgroupware-developers] PGW in multi-location setup

[Thomas Bott]

We are running a multi-(9)-location environment. (Linux) user/ group
management, email-routing, etc is replicated by LDAP. 

We are going to integrate pgw and tested it so far in one location [head
office]. Now we are about to begin the next step and are going to run pgw in a
second location. We are looking for a 2-way-replication for addressbook,
calendar, infolog, ... and a one-way-replication for user-, group,
acl-management. Later on, all 9 locations should replicate their application
data and recieve user-, group- and ACL information from one location only, the
head office.

We've been thinking about the issue and found two possible ways - using MySQL
for replication or using the pgw peer-server service.
##
## MySQL replication
##
All 9 locations are connected in a circular master/slave relationship. After
completing a circle the data is replicated to all locations. If a connections
fails, the slave reconnects automatically to get the missed updates. But this
circular setup works only if you perform no conflicting updates between the
tables. In other words, if you insert data in both servers, you should never
insert a row in server A that may have a key that conflicts with a row inserted
in B.

1. 
To avoid conflicting keys, each server gets a separate key-space, e.g.
0-9,999,999 for server A and 10,000,000-19,999,999 for server B. This way,each
time you are inserting a new addressbook, calendar, ... entry pgw has to
recalculate the appropriate next free key - but not for user-management and
ACLs.

2.
Another way to avoid conflicting keys is to run a separate database for each
location that is replicated to each location. This way, pgw has to query
multiple databases to get e.g. all  events for a day or all available addresses
but not for user-management and ACLs.

##
## pgw - peer server
##
After searching the docs and the wiki
[http://wiki.phpgroupware.org/index.php?page=PeerServers] , we are not sure
about the functionality and status of the "peer-server" service. We prefer the
pgw way. So can the replication be accomplished by using peer servers and is
the replication process reliable?

Because pgw fulfills nearly all our needs, we really want to find a solution
for this multi-location issue. Any comments are appreciated, even if they're
hints how we can add the missing/additional functionality to pgw.

Regards,

Thomas Bott, Christian Rost