Hi Mircea,

I'm in the process of setting up the Infinispan GUI demo across 3 data
centers, and I ran into an issue with the Infinispan config file. Not
really a bug, but something that could be improved.

Currently, the Infinispan config (let's call it infinispan.xml) defines
the sites and their backup sites and refers to the local JGroups cluster
config file (jgroups.xml). The latter has a RELAY2 protocol at the top
of its stack which points to the relay configuration (relay2.xml), which
defines the sites and how they connect to each other. Finally, there's a
jgroups-relay2.xml file (referred to from relay2.xml) which defines the
global bridge, connecting all 3 sites.

OK, so that 4 config files and I don't see how to reduce them.
However... currently infinispan.xml is *site-specific*, ie. we need 1
infinispan.xml for LON, 1 for SFO and 1 for NYC.

The 3 JGroups config files (jgroups.xml, relay2.xml and
relay2-bridge.xml) are *not* site-specific, ie. they can be used in any
site, provided that we set a few system properties, such as
cluster-specific mcast address and port, and site name (relay2.xml).

I believe cross-site clustering would benefit from making infinispan.xml
symmetric as well, that is, we could use it in any site.

To do this, I suggest the following:

#1 Sites config:
 <sites local="LON">
            <site name="SFO"/>
            <site name="NYC"/>
            <site name="LON"/>
        </sites>


Nothing needs to be changed here, except to parameterize local: <sites
local="${SITE:LON}"...>. A node in a given site can then be started
using -DSITE=LON. This could also be used for relay2.xml.

- Question-1: why do we need to list the sites above ? We're not
defining any config for those sites, so I don't see why this is needed...

#2 Backups config:
 <namedCache name="users">
        <sites>
            <backups>
                <backup site="NYC" backupFailurePolicy="WARN"
strategy="SYNC" timeout="12000"/>
                <backup site="SFO" backupFailurePolicy="IGNORE"
strategy="ASYNC"/>
            </backups>
        </sites>
    </namedCache>


This is *asymmetric*. IMO, a better config would be:

<global>
  <sites>
       <localSite="${site:LON}" backupSites="${backup-sites:SFO,NYC}" />
       <backups>
                <backup site="NYC" backupFailurePolicy="WARN"
strategy="SYNC" timeout="12000"/>
                <backup site="SFO" backupFailurePolicy="IGNORE"
strategy="ASYNC"/>
                <backup site="LON" backupFailurePolicy="IGNORE"
strategy="ASYNC"/>
       </backups>
   </sites>
</global>


Here, we define global backup strategies and the local site. Both of
them can be parameterized, e.g. we start up nodes in
- LON: -Dsite=LON -DbackupSites="SFO,NYC"
- SFO: -Dsite=SFO -DbackupSites=NYC
- NYC: -Dsite=NYC -DbackupSites=     // no backups


This would allow us to have only 1 infinispan.xml, regardless of the
site in which it is used.

Of course, since backup strageties are globally defined, if people
wanted different backup strategies per site (or per named cache), they
could still copy infinispan.xml and modify it...

WDYT ?




--
Bela Ban, JGroups lead (http://www.jgroups.org)
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