tolbertam / gremlin-scala-dse-example

DataStax Enterprise Graph with gremlin-scala Example

DataStax Enterprise Graph with gremlin-scala Example

Note: This example has been superceded by the dse-graph example in gremlin-scala-examples. This example is left in tact, but in the future it may become out of date, refer to gremlin-scala-examples for up to date examples.

This repository provides a basic example of using gremlin-scala and the Java driver for DataStax Enterprise to interact with a DataStax Enterprise Graph.

How it works

The DSE driver includes a library dse-java-driver-graph for creating an Apache TinkerPop remote GraphTraversalSource. You can read more about this integration on the Apache TinkerPop client integration page in the driver manual:

val dseCluster = DseCluster.builder()
  .addContactPoint("127.0.0.1")
  .build()

val session = dseCluster.connect()

// Use DseGraph API to create a GraphTraversalSource from a previously connected session.
val g: GraphTraversalSource = DseGraph.traversal(session, graphOptions)

To enable gremlin-scala, all one needs to do is import it:

import gremlin.scala._

From here, the scala friendly function signatures provided from gremlin-scala are available on the driver-created GraphTraversalSource.

Refer to GremlinScalaApp.scala for a very basic example of how to accomplish this.

Workarounds needed to successfully build project

There are a few workarounds needed to use TinkerPop and the dse driver with scala that you should be aware of:

1. jBCrypt, a dependency of TinkerPop, does not resolve with default SBT settings. This will be fixed in a future TinkerPop release (see: TINKERPOP-1633), for now declaring jitpack as a resolver can be used as a workaround.

2. There is a weakness in the scala compiler that prevents code from using DseCluster from compiling. To work around this, -Ybreak-cycles needs to be added to scalacOptions.
   See JAVA-1252 for more detail.

Setting up a Local DSE Node for Testing

To run the tests, you first need to set up a local DSE node that is preconfigured. The simplest way to accomplish this is to use ccm, but you may use an alternative means if you like. The following steps demonstrate how to set up a single-node DSE ccm cluster with graph enabled:

1. Create the ccm cluster (with username and password being that which you use to download DSE normally):

   ccm create -n 1 -v 5.1.0 --dse dse510_1 --dse-username=username --dse-password=password

2. Enable the Graph workload:

   ccm setworkload graph

3. Start the ccm cluster

   ccm start

Running the Example

To build and run the example, simply execute ./sbt run which will compile and run GremlinScalaApp.scala. If everything goes well, the output should look like:

gremlin-scala-dse-example $ ./sbt run
[warn] Executing in batch mode.
[warn]   For better performance, hit [ENTER] to switch to interactive mode, or
[warn]   consider launching sbt without any commands, or explicitly passing 'shell'
[info] Loading project definition from /Users/atolbert/Documents/Projects/gremlin-scala-dse-example/project
[info] Set current project to gremlin-scala-dse-example (in build file:/Users/atolbert/Documents/Projects/gremlin-scala-dse-example/)
[info] Updating {file:/Users/atolbert/Documents/Projects/gremlin-scala-dse-example/}gremlin-scala-dse-example...
[info] Resolving jline#jline;2.14.1 ...
[info] Done updating.
[info] Compiling 1 Scala source to /Users/atolbert/Documents/Projects/gremlin-scala-dse-example/target/scala-2.12/classes...
[warn] Breaking cycle in base class computation of class Cluster in com.datastax.driver.core (List(class Cluster, trait Closeable, trait AutoCloseable, class Object, class Any))
[warn] one warning found
[info] Running am.tolbert.gremlin.GremlinScalaApp 
13:33:45.842 INFO  c.d.d.c.GuavaCompatibility - Detected Guava >= 19 in the classpath, using modern compatibility layer
13:33:46.015 INFO  c.d.d.c.ClockFactory     - Using native clock to generate timestamps.
13:33:46.063 INFO  a.t.g.GremlinScalaApp$   - Connecting to DSE
13:33:46.106 INFO  c.d.d.c.NettyUtil        - Did not find Netty's native epoll transport in the classpath, defaulting to NIO.
13:33:46.625 INFO  c.d.d.c.p.DCAwareRoundRobinPolicy - Using data-center name 'Graph' for DCAwareRoundRobinPolicy (if this is incorrect, please provide the correct datacenter name with DCAwareRoundRobinPolicy constructor)
13:33:46.628 INFO  c.d.d.c.Cluster          - New Cassandra host /127.0.0.1:9042 added
13:33:46.641 INFO  a.t.g.GremlinScalaApp$   - Creating graph example
13:33:46.847 INFO  a.t.g.GremlinScalaApp$   - Enabling development mode
13:33:46.891 INFO  a.t.g.GremlinScalaApp$   - Allowing scans
13:33:46.979 INFO  a.t.g.GremlinScalaApp$   - Creating vertex
13:33:47.273 INFO  a.t.g.GremlinScalaApp$   - Retrieving 'age' property of created Vertex
13:33:47.299 INFO  a.t.g.GremlinScalaApp$   - Response: {age=[29]}
13:33:47.299 INFO  a.t.g.GremlinScalaApp$   - Disconnecting
13:33:49.539 INFO  a.t.g.GremlinScalaApp$   - Done
[success] Total time: 11 s, completed Apr 19, 2017 1:33:50 PM