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Hibernate Second Level Cache

Hazelcast provides distributed second level cache for your Hibernate entities, collections and queries.

Sample Code for Hibernate

Please see our sample application for Hibernate Second Level Cache.

Supported Hibernate Versions

  • hibernate 3.3.x+
  • hibernate 4.x

Configuring Hibernate for Hazelcast

To configure Hibernate for Hazelcast:

  • Add hazelcast-hibernate3-<hazelcastversion>.jar or hazelcast- hibernate4-<hazelcastversion>.jar into your classpath depending on your Hibernate version.
  • Then add the following properties into your Hibernate configuration file (e.g. hibernate.cfg.xml).

Enabling Second Level Cache

<property name="hibernate.cache.use_second_level_cache">true</property>

Configuring RegionFactory

You can configure Hibernate RegionFactory with HazelcastCacheRegionFactory or HazelcastLocalCacheRegionFactory.

HazelcastCacheRegionFactory

HazelcastCacheRegionFactory uses standard Hazelcast Distributed Maps to cache the data, so all cache operations go through the wire.

<property name="hibernate.cache.region.factory_class">
   com.hazelcast.hibernate.HazelcastCacheRegionFactory
</property>

All operations like get, put, and remove will be performed using the Distributed Map logic. The only downside of using HazelcastCacheRegionFactory may be lower performance compared to HazelcastLocalCacheRegionFactory since operations are handled as distributed calls.

image NOTE: If you use HazelcastCacheRegionFactory, you can see your maps on Management Center.

With HazelcastCacheRegionFactory, all of the following caches are distributed across Hazelcast Cluster.

  • Entity Cache
  • Collection Cache
  • Timestamp Cache
HazelcastLocalCacheRegionFactory

You can use HazelcastLocalCacheRegionFactory which stores data in a local node and sends invalidation messages when an entry is updated/deleted locally.

<property name="hibernate.cache.region.factory_class">
  com.hazelcast.hibernate.HazelcastLocalCacheRegionFactory
</property>

With HazelcastLocalCacheRegionFactory, each cluster member has a local map and each of them is registered to a Hazelcast Topic (ITopic). Whenever a put or remove operation is performed on a member, an invalidation message is generated on the ITopic and sent to the other members. Those other members remove the related key-value pair on their local maps as soon as they get these invalidation messages. The new value is only updated on this member when a get operation runs on that key. In the case of get operations, invalidation messages are not generated and reads are performed on the local map.

An illustration of the above logic is shown below.

image

If your operations are mostly reads, then this option gives better performance.

image NOTE: If you use HazelcastLocalCacheRegionFactory, you cannot see your maps on Management Center.

With HazelcastLocalCacheRegionFactory, all of the following caches are not distributed and are kept locally in the Hazelcast Node.

  • Entity Cache
  • Collection Cache
  • Timestamp Cache

Entity and Collection are invalidated on update. When they are updated on a node, an invalidation message is sent to all other nodes in order to remove the entity from their local cache. When needed, each node reads that data from the underlying DB.

Timestamp cache is replicated. On every update, a replication message is sent to all the other nodes.

Eviction support is limited to maximum size of the map (defined by max-size configuration element) and TTL only. When maximum size is hit, 20% of the entries will be evicted automatically.

Configuring Query Cache and Other Settings

  • To enable use of query cache:

    <property name="hibernate.cache.use_query_cache">true</property>

  • To force minimal puts into query cache:

    <property name="hibernate.cache.use_minimal_puts">true</property>

  • To avoid NullPointerException when you have entities that have composite keys (using @IdClass):

    <property name="hibernate.session_factory_name">yourFactoryName</property>

image NOTE: QueryCache is always LOCAL to the node and never distributed across Hazelcast Cluster.

Configuring Hazelcast for Hibernate

To configure Hazelcast for Hibernate, put the configuration file named hazelcast.xml into the root of your classpath. If Hazelcast cannot find hazelcast.xml, then it will use the default configuration from hazelcast.jar.

You can define a custom-named Hazelcast configuration XML file with one of these Hibernate configuration properties.

<property name="hibernate.cache.provider_configuration_file_resource_path">
  hazelcast-custom-config.xml
</property>

<property name="hibernate.cache.hazelcast.configuration_file_path">
  hazelcast-custom-config.xml
</property>

Hazelcast creates a separate distributed map for each Hibernate cache region. You can easily configure these regions via Hazelcast map configuration. You can define backup, eviction, TTL and Near Cache properties.

Setting P2P (Peer-to-Peer) for Hibernate

Hibernate Second Level Cache can use Hazelcast in two modes: Peer-to-Peer (P2P) and Client/Server (next section).

With P2P mode, each Hibernate deployment launches its own Hazelcast Instance. You can also configure Hibernate to use an existing instance, instead of creating a new HazelcastInstance for each SessionFactory. To do this, set the hibernate.cache.hazelcast.instance_name Hibernate property to the HazelcastInstance's name. For more information, please see Named Instance Scope.

Disabling shutdown during SessionFactory.close()

You can disable shutting down HazelcastInstance during SessionFactory.close(). To do this, set the Hibernate property hibernate.cache.hazelcast.shutdown_on_session_factory_close to false. (In this case, you should not set the Hazelcast property hazelcast.shutdownhook.enabled to false.) The default value is true.

Setting Client/Server for Hibernate

You can set up Hazelcast to connect to the cluster as Native Client. Native client is not a member; it connects to one of the cluster members and delegates all cluster wide operations to it. Client instance started in the Native Client mode uses Smart Routing: when the relied cluster member dies, the client transparently switches to another live member. All client operations are Retry-able, meaning that the client resends the request as many as 10 times in case of a failure. After the 10th retry, it throws an exception. You cannot change the routing mode and retry-able operation configurations of the Native Client instance used by Hibernate 2nd Level Cache. Please see the Smart Routing section and Retry-able Operation Failure section for more details.

<property name="hibernate.cache.hazelcast.use_native_client">true</property>

To set up Native Client, add the Hazelcast group-name, group-password and cluster member address properties. Native Client will connect to the defined member and will get the addresses of all members in the cluster. If the connected member dies or leaves the cluster, the client will automatically switch to another member in the cluster.

<property name="hibernate.cache.hazelcast.native_client_address">10.34.22.15</property>
<property name="hibernate.cache.hazelcast.native_client_group">dev</property>
<property name="hibernate.cache.hazelcast.native_client_password">dev-pass</property>

image NOTE: To use Native Client, add hazelcast-client-<version>.jar into your classpath. Refer to Clients for more information.

image NOTE: To use Native Client, add hazelcast-all-<version>.jar into your remote cluster's classpath.

Configuring Cache Concurrency Strategy

Hibernate has four cache concurrency strategies: read-only, read-write, nonstrict-read-write and transactional. Hibernate does not force cache providers to support all those strategies. Hazelcast supports the first three: read-only, read-write, and nonstrict-read-write. It does not yet support transactional strategy.

If you are using XML based class configurations, add a cache element into your configuration with the usage attribute set to one of the read-only, read-write, or nonstrict-read-write strategies.

<class name="eg.Immutable" mutable="false">
  <cache usage="read-only"/>
  .... 
</class>

<class name="eg.Cat" .... >
  <cache usage="read-write"/>
  ....
  <set name="kittens" ... >
    <cache usage="read-write"/>
    ....
  </set>
</class>

If you are using Hibernate-Annotations, then you can add a class-cache or collection-cache element into your Hibernate configuration file with the usage attribute set to read only, read/write, or nonstrict read/write.

<class-cache usage="read-only" class="eg.Immutable"/>
<class-cache usage="read-write" class="eg.Cat"/>
<collection-cache collection="eg.Cat.kittens" usage="read-write"/>

Or alternatively, you can put Hibernate Annotation's @Cache annotation on your entities and collections.

@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class Cat implements Serializable {
  ...
}

Advanced Settings

Accessing underlying HazelcastInstance

If you need to access HazelcastInstance used by Hibernate SessionFactory, you can give a name to the HazelcastInstance while configuring Hazelcast. Then it is possible to retrieve the instance using getHazelcastInstanceByName static method of Hazelcast.

Please refer to the Configuration Overview section to learn how to create a named Hazelcast instance.

Changing/setting lock timeout value of read-write strategy

You can set a lock timeout value using the hibernate.cache.hazelcast.lock_timeout_in_seconds Hibernate property. The value should be in seconds. The default value is 300 seconds.