A couple weeks ago saw the final release of JBoss AS 7.0. Like AS6 before it, AS7 uses Infinispan as the distributed caching solution behind its clustering functionality. So what do you need to know about using Infinispan in AS7?
Configuration
Unlike previous releases of JBoss AS, AS7 centralizes all server configuration into one location. This include Infinispan cache configurations, which are defined by the Infinispan subsystem, within domain.xml or standalone.xml:
The complete schema for the Infinispan subsystem is included in the AS7 binary distribution:
If you are familiar with Infinispan's native configuration file format or the corresponding configuration file from AS6, you'll notice some obvious similarities, but some noteworthy differences.
While a native Infinispan configuration file contains cache configurations for a single cache container, like AS6, the Infinispan subsystem configuration defines multiple cache containers, each identified by a name. As with AS6, cache containers can have 1 or more aliases.
Being concise
The Infinispan subsystem's configuration schema attempts to be more concise than the equivalent configuration in AS6. This is a direct result of the following changes:
Where is <global/>?
Much of the global configuration contains references to other AS services. In AS7, these services are auto-injected behind the scenes. This includes things like thread pools (described below), the JGroups transport (also described below), and the mbean server.
Configuration default values
AS7 supplies a set of custom default values for various configuration properties. These defaults differ depending on the cache mode. The complete set of default values can be found here:
File-based cache store
Because clustering services use the file-based cache store frequently, we've simplified its definition. First, by using a distinctive element, you no longer need to specify the class name. The location of the store is defined by 2 attributes:
<file-store relative-to="..." path="..."/>
The
relative-to attribute defines a named path, and defaults to the server's data directory; whereas the
path attribute specifies the directory within
relative-to, and defaults to the cache container name.
Specifying cache mode
Instead of defining the cache mode via a separate <clustering mode="..."/> attribute, each cache mode uses it's own element, the child elements of which are specific to that cache mode. For example, rehashing properties are only available within the <distributed-cache/> element.
Where is <default/>?
The semantics of the default cache of a cache container are different in AS7 than in native Infinispan. In native Infinispan, the configuration within <default/> defines the cache returned by calls to
CacheContainer.getCache(), while <namedCache/> entries inherit the configuration from the default cache.
In AS7, all caches defined in the Infinispan subsystem are named caches. The
default-cache attribute identifies which named cache should be returned by calls to
CacheContainer.getCache(). This lets you easily modify the default cache of a cache container, without having to worry about rearranging configuration property inheritance.
Specifying a transport
The Infinispan subsystem uses with the JGroups subsystem to provide it's JGroups channel. By default, cache containers use the
default-stack as defined by the JGroups subsystem.
<subsystem xmlns="urn:jboss:domain:jgroups:1.0" default-stack="udp">
<stack name="udp">
<!-- ... -->
</stack>
<stack name="tcp">
<!-- ... -->
</stack>
</subsystem>
Changing the default stack for all clustering services is a simple as changing the
default-stack attribute defined in the JGroups subsystem. An individual cache-container can opt to use a particular stack by specifying a
stack attribute within its
transport element.
e.g.
<cache-container name="web" default-cache="repl">
<transport stack="tcp"/>
<replicated-cache name="repl" mode="ASYNC" batching="true">
<locking isolation="REPEATABLE_READ"/>
<file-store/>
</replicated-cache>
</cache-container>
JGroups channels are named using the cache container name.
Defining thread pools
Cache containers defined by the Infinispan subsystem can reference thread pools defined by the threading subsystem. Externalizing thread pool in this way has the additional advantage of being able to manage the thread pools via native JBoss AS management mechanisms, and allows you to share thread pools across cache containers.
e.g.
<cache-container name="web" default-cache="repl" listener-executor="infinispan-listener" eviction-executor="infinispan-eviction" replication-queue-executor="infinispan-repl-queue">
<transport executor="infinispan-transport"/>
<replicated-cache name="repl" mode="ASYNC" batching="true">
<locking isolation="REPEATABLE_READ"/>
<file-store/>
</replicated-cache>
</cache-container>
<subsystem xmlns="urn:jboss:domain:threads:1.0">
<thread-factory name="infinispan-factory" priority="1"/>
<bounded-queue-thread-pool name="infinispan-transport"/>
<core-threads count="1"/>
<queue-length count="100000"/>
<max-threads count="25"/>
<thread-factory name="infinispan-factory"/>
</bounded-queue-thread-pool>
<bounded-queue-thread-pool name="infinispan-listener"/>
<core-threads count="1"/>
<queue-length count="100000"/>
<max-threads count="1"/>
<thread-factory name="infinispan-factory"/>
</bounded-queue-thread-pool>
<scheduled-thread-pool name="infinispan-eviction"/>
<max-threads count="1"/>
<thread-factory name="infinispan-factory"/>
</scheduled-thread-pool>
<scheduled-thread-pool name="infinispan-repl-queue"/>
<max-threads count="1"/>
<thread-factory name="infinispan-factory"/>
</scheduled-thread-pool>
</subsystem>
Cache container lifecycle
During AS6 server startup, the
CacheContainerRegistry service would create and start all cache containers defined within its
infinispan-configs.xml file. Individual caches were started and stopped as needed. Lifecycle control of a cache was the complete responsibility of the application or service that used it.
Instead of a separate
CacheContainerRegistry, AS7 uses the generic
ServiceRegistry from the jboss-msc project (i.e. JBoss Modular Service Container). When AS7 starts, it creates on-demand services for each cache and cache container defined in the Infinispan subsystem. A service or deployment that needs to use a given cache or cache container simply adds a dependency on the relevant service name. When the service or deployment stops, dependent services are stopped as well, provided they are not still demanded by some other service or deployment. In this way, AS7 handles cache and cache container lifecycle for you.
There may be an occasion where you'd like a cache to start eagerly when the server starts, without requiring a dependency from some service or deployment. This can be achieve by using the start attribute of a cache.
e.g.
<cache-container name="cluster" default-cache="default">
<alias>ha-partition</alias>
<replicated-cache name="default" mode="SYNC" batching="true" start="EAGER">
<locking isolation="REPEATABLE_READ"/>
</replicated-cache>
</cache-container>
Using an Infinispan cache directly
AS7 adds the ability to inject an Infinispan cache into your application using standard JEE mechanisms. This is perhaps best explained by an example:
@ManagedBean
public class MyBean<K, V> {
@Resource(lookup="java:jboss/infinispan/my-container-name")
private org.infinispan.manager.CacheContainer container;
private org.infinispan.Cache<K, V> cache;
@PostConstruct
public void start() {
this.cache = this.container.getCache();
}
}
That's it! No JBoss specific classes required - only standard JEE annotations. Pretty neat, no?
There's only one catch - due to the AS's use of modular classloading, Infinispan classes are not available to deployments by default. You need to explicitly tell the AS to import the Infinispan API into your application. This is most easily done by adding the following line to your application's
META-INF/MANIFEST.MF:
Dependencies: org.infinispan export
So, how does it all work? If you recall, during server startup, the AS creates and registers an on-demand service for every Infinispan cache container defined in the Infinispan subsystem. For every cache container, the Infinispan subsystem also creates and registers a JNDI binding service that depends on the associated cache container service. When the AS deployer encounters the
@Resource(lookup) annotation, it automatically adds a dependency to the application on the JNDI binding service associated with the specified JNDI name. In the case of the Infinispan JNDI binding, the binding itself already depends on the relevant Infinispan cache container service. The net effect is, your application will include a dependency on the requested cache container. Consequently, the cache container will automatically start on deploy, and stop (including all caches) on undeploy.
Sounds great! Where do I get it?
You can download the JBoss AS 7.0.0 Final release here:
User documentation can be found here:
And direct any questions to the user forums:
Keep a look out for the 7.0.1 release expected in the coming weeks, which contains a number of clustering fixes identified since the initial final release.
How can I contribute?
Here's the best place to start:
