Migrating projects from one container to another is often problematic. Not as
much with Infinispan. This article is about configuring Infinispan,
using Transaction Manager for demarcating transaction boundaries, while keeping the data both in a memory and relational database - stored via JDBC cache store. I'll demonstrate all the features on code snippets.
A complete application is located at https://github.com/mgencur/infinispan-examples
and is called carmart-tx-jdbc. It's a web application based on JSF 2,
Seam 3 and Infinispan 5.1.4.FINAL, is fully working, tested with JBoss
Application Server 7.1.1.Final and Tomcat 7.0.27. There is one
prerequisite, though. It needs an installed and working MySQL database
in your system. The database name should be carmartdb, accessible by a
user with carmart/carmart username/password.
First, look at what we need to configure for JBoss Application Server 7.
Configuring transactions and JDBC cache store on JBoss AS 7
Infinispan
will be configured via new fluent API using builders, hence the call
to .build() method at the end. We need to configure aspects related to
transactions and cache loaders. The configuration API for cache
loaders is likely going to be changed in not-so-far future. It should
be fluent and more intuitive, generally easier to use than current
one.
I purposely do not show XML configuration. Configuration examples can be found at https://github.com/infinispan/infinispan/blob/master/core/src/main/resources/config-samples/sample.xml.
In order to configure transactions and cache loaders, look for tags
called <transaction> and <loaders> and modify that sample
file according to below configuration. Tag names and attribute names are
very similar for both XML and Java configuration. If that is not
enough, there is always a schema in Infinispan distribution.
The configuration of Infinispan is as follows:
Lines marked with red are different in other containers/configurations, as you'll see in a minute. The code above implies that we need to specify proper TransactionManagerLookup implementation which is, in this case, GenericTransactionManagerLookup. We also need to say: "Hey, I wanna use
ManagedConnectionFactory as a connectionFactoryClass". OK, here we go. I should, as well, explain how to configure a datasource properly, right? In JBoss AS 7, this is configured as a subsystem in $JBOSS_HOME/standalone/configuration/standalone.xml:
The usage of transactions is very simple as we can obtain a transaction object by injection.
Sources:
https://github.com/mgencur/infinispan-examples/blob/master/carmart-tx-jdbc/src/jbossas/java/org/infinispan/examples/carmart/session/CarManager.java
Quite
easy, isn't it ...if you know how to do it. The only problem is that it
does not work (at least not completely) :-) If you deploy the app, you
find out that when storing a key-value pair in the cache, an exception
is thrown. This exception indicates that the operation with DB (and JDBC
cache store) failed. The exception says:
A complete stack trace looks similar to https://gist.github.com/2777348
There's still an open issue in JIRA (ISPN-604) and it is being worked on.
Configuring transactions and JDBC cache store on JBoss AS 7 - c3p0
But
how do we cope with this inconvenience for now... By not using a
managed datasource but rather a third party library called c3p0 (JDBC3
Connection and Statement Pooling, more information at http://www.mchange.com/projects/c3p0/index.html)
Infinispan allows you to use this library for connecting to the
database. If you really want to use it, you need to choose a different
connectionFactoryClass which is, in this case, PooledConnectionFactory.
Infinispan configuration looks like this:
Transactions
are accessible in the same way as in the previous use case. Now let's
look at configuration for Tomcat servlet container.
Configuring transactions and JDBC cache store on Tomcat 7
Tomcat
does not have any Transaction Manager in it so we have to bundle one
with the application. For the purpose of this exercise, we choose JBoss
Transactions (http://www.jboss.org/jbosstm). See dependencies at the end.
Cache manager and cache configuration is in this form:
For
Tomcat, we need to specify a different transactionManagerLookup
implementation and datasourceJndiLocation. Tomcat simply places objects
under a bit different JNDI locations. The datasource is defined in
context.xml file which has to be on classpath. This file might look like
this:
How do we get the transaction manager in the application then? Lets obtain it directly from a cache.
Infinispan knows how to find the manager and we need to know how to obtain it from Infinispan.
Sources:
https://github.com/mgencur/infinispan-examples/blob/master/carmart-tx-jdbc/src/tomcat/java/org/infinispan/examples/carmart/session/CarManager.java The transaction manager provides standard methods for transactions, such as begin(), commit() and rollback().
Now is the time for dependencies
So...which
dependencies do we always need when using Infinispan with JDBC cache
stores and transactions? These are infinspan-core,
infinispan-cachestore-jdbc and javax.transaction.jta. The scope for jta
dependency, as defined in Maven, is different for JBossAS and Tomcat.
Common dependencies for JBossAS and Tomcat
Of
course, our application needs a few more dependencies but these are not
directly related to Infinispan. Let's ignore them in this article.
JBoss AS 7 provides managed datasource that is accessible from
Infinispan. The only specific dependency (related to transactions or
Infinispan) is JTA.
Dependencies specific to JBossAS - using managed Datasource (managed by the server)
Dependencies specific to JBossAS - using c3p0
Yes,
you need to bundle also MySQL connector. On the other hand, for Tomcat
use case and JBossAS with managed datasource, this jar file needs do be
deployed to the server separately. For Tomcat, do this simply by copying
the jar file to $TOMCAT_HOME/lib. For JBoss AS 7, copy the jar file
into $JBOSS_HOME/standalone/deployments.
Dependencies specific to Tomcat - using JBoss Transactions
That's it. I hope you've found this article helpful. Any feedback is welcome, especially the positive one :-) If you find any problem with the
application, feel free to comment here or participate in Infinispan forums (
http://www.jboss.org/infinispan/forums).
Martin
