Chapter 6. Remote Querying


Red Hat JBoss Data Grid's Hot Rod protocol allows remote, language neutral querying.
Two features allow this to occur:
The Infinispan Query Domain-specific Language (DSL)

JBoss Data Grid uses its own query language based on an internal DSL. The Infinispan Query DSL provides a simplified way of writing queries, and is agnostic of the underlying query mechanisms. Querying via the Hot Rod client allows remote, language-neutral querying, and is implementable in all languages currently available for the Hot Rod client.

The Infinispan Query DSL is essential for performing remote queries, but can be used in both embedded and remote mode.
Protobuf Encoding

Google's Protocol Buffers is used as an encoding format for both storing and querying data. The Infinispan Query DSL can be used remotely via the Hot Rod client that is configured to use the Protobuf marshaller. Protocol Buffers are used to adopt a common format for storing cache entries and marshalling them.

Remote clients that need to index and query their stored entities must use the Protobuf encoding format. It is also possible to store Protobuf entities for the benefit of platform independence without indexing enabled if it is not required.

Warning

The Infinispan Query DSL and Remote Querying described in this chapter are Technology Preview and not supported in JBoss Data Grid 6.2.

6.1. Performing Remote Queries via the Java Hot Rod Client

Remote querying over Hot Rod can be enabled once the RemoteCacheManager has been configured with the Protobuf marshaller.
The following procedure describes how to enable remote querying over its caches.
Prerequisites

RemoteCacheManager must be configured to use the Protobuf Marshaller.

Procedure 6.1. Enabling Remote Querying via Hot Rod

  1. Add All Relevant Dependencies

    See the infinispan-client-hotrod dependencies in the runtime-classpath.txt file in the JBoss Data Grid Library distribution for a full list of required dependencies.
  2. Enable indexing on the cache configuration.

    This is the same as for Library mode. See Section 2.2, “Configure Infinispan Query”
  3. Register the Protobuf Binary Descriptor

    Register the Protobuf binary descriptor by invoking the registerProtofile method of the server's ProtobufMetadataManager MBean. There is one instance of this per EmbeddedCacheManager.
Result

All data placed in the cache is now being indexed without the need to annotate entities. These classes are only meaningful to the Java client, and do not exist on the server.

Once remote querying has been enabled, the QueryFactory can be obtained using the following:
import org.infinispan.client.hotrod.Search;
import org.infinispan.query.dsl.QueryFactory;
import org.infinispan.query.dsl.Query;
...
remoteCache.put(2, new User("John", "Doe", 33));
QueryFactory qf = Search.getQueryFactory(remoteCache);
Query query = qf.from(User.class)
    .having("name").eq("John")
    .toBuilder().build();
List list = query.list();
assertEquals(1, list.size());
assertEquals("John", list.get(0).getName());
assertEquals("Doe", list.get(0).getSurname());

Queries can now be run over Hot Rod similar to Library mode.
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