Titan - How to Use 'Lucene' Search Backend - titan

Question

I am attempting to use the lucene search backend with Titan. I am setting the index.search.backend property to lucene as so.
TitanFactory.Builder config = TitanFactory.build();
config.set("storage.backend", "hbase");
config.set("storage.hostname", "node1");
config.set("storage.hbase.table", "titan");
config.set("index.search.backend", "lucene");
config.set("index.search.directory", "/tmp/foo");
TitanGraph graph = config.open();
GraphOfTheGodsFactory.load(graph);
graph.getVertices().forEach(v -> System.out.println(v.toString()));
Of course, this does not work because this setting is of the GLOBAL_OFFLINE variety. The logs make me aware of this. Titan ignores my 'lucene' setting and then attempts to use Elasticsearch as the search backend.
WARN com.thinkaurelius.titan.graphdb.configuration.GraphDatabaseConfiguration
- Local setting index.search.backend=lucene (Type: GLOBAL_OFFLINE)
is overridden by globally managed value (elasticsearch). Use
the ManagementSystem interface instead of the local configuration to control
this setting.
After some reading, I understand that I need to use the Management System to set the index.search.backend. I need some code that looks something like the following.
graph.getManagementSystem().set("index.search.backend", "lucene");
graph.getManagementSystem().set("index.search.directory", "/tmp/foo");
graph.getManagementSystem().commit();
I am confused on how to integrate this in my original example code above. Since this is a GLOBAL_OFFLINE setting, I cannot set this on an open graph. At the same time, I do not know how to get a graph unless I open one first. How do I set the search backend correctly?

Answer 1

There is no inmemory search backend. The supported search backends are Lucene, Solr, and Elasticsearch.
Lucene is a good option for a small scale, single machine search backend. You need to set 2 properties to do this, index.search.backend and index.search.directory:
index.search.backend=lucene
index.search.directory=/path/to/titansearchindexdir
As you've noted, the search backend is a GLOBAL_OFFLINE, so you should configure this before initially creating your graph. Since you've already created a titan table in your HBase, either disable and drop the titan table, or set your graph configuration to point at a new storage.hbase.table.