titan-tp3-driver-example | Example Java program using Titan | Graph Database library

1. If that query is taking a long time, the problem is likely that it is visiting too many elements or it is stuck in an infinite loop. The existing JanusGraph/Titan indexes won't help for that. You already have a direct vertex lookup by id, g.V(vertexId), and the rest of the query is traversing the neighborhood from that vertex. I'd suggest using edge labels, i.e. out('friends'), to limit the number of edges you visit. You could also use simplePath() to eliminate cyclic paths. You could also use times() or until() to keep a limit on the number of times you loop with the repeat() step.

2. The configuration example you referenced only used composite indexes, which do not require an indexing backend.

Mixed indexes require configuring an indexing backend, either Elasticsearch, Lucene, or Solr. Pick one of these, then make sure you pass the correct configuration properties when you initialize your graph. You can find several examples in the distribution zip file in the conf directory. For example, in the janusgraph-cassandra-es.properties, you'll find:

The problem was forgetting to use Parameterized Scripts http://tinkerpop.apache.org/docs/current/reference/#parameterized-scripts

Gremlin Server caches all scripts that are passed to it: using Parameterized Scripts reduces caching because only not common scripts are cached (g.V(x))

Not using Parameterized Scripts and using instead String.format for example (like we did) implies caching all gremlin scripts separately which is very expensive and causes an OutOfMemoryError

I hope this would help someone ;)