Hello.
On Jul 31, 2006, at 17:52, Borut Bolčina wrote:
I need an advice on using Cayenne in an environment where two
PostgeSQL databases are configured to replicate from each other
for failover capability.
Are you using Sequoia[1] or slony[2] or creating your own solution?
I am thinking of two Cayenne enabled applications (load
distribution) which insert records in one of those two databases.
Application one (A1) inserts in database one (DB1) and application
two (A2) inserts in database two (DB2).
The insertion, deletion or update will cause Java triggers in
PostgreSQL to call appropriate Java method in the application. If
for any reason one of the databases is down for some time, the
replication mechanism will bring the second database up-to date
which will trigger invocations of the Java methods, so the second
application will be in the correct state also.
As long as triggers do not modify records, everything should be ok
with Cayenne. In case, which I don't foresee now, the records will
be modified on database level, all DataContexts should be
invalidated, am I right?
Cayenne has its own way of syncronizing cache[3] between app
instances. You could also invalidate cache manually.
- Tore.
[1] http://sequoia.continuent.org/HomePage
[2] http://gborg.postgresql.org/project/slony1/
[3] http://cwiki.apache.org/CAYDOC/configuring-caching-behavior.html
