The JanusGraph release comes pre-configured to run JanusGraph Server out of the box leveraging a sample Cassandra and ElasticSearch configuration to allow users to get started quickly with JanusGraph Server. This configuration defaults to client applications that can connect to JanusGraph Server via WebSockets with a custom subprotocol. There are a number of clients developed in different languages to help support the subprotocol. The most familiar client to use the WebSocket interface is the gremlin.sh shell. The quick-start bundle is not intended to be representative of a production installation, but does provide a way to perform development with JanusGraph Server, run tests and see how the components are wired together. To use this default configuration:

$ bin/janusgraph.sh start
Forking Cassandra...
Running `nodetool statusthrift`.. OK (returned exit status 0 and printed string "running").
Forking Elasticsearch...
Connecting to Elasticsearch (127.0.0.1:9300)... OK (connected to 127.0.0.1:9300).
Forking Gremlin-Server...
Connecting to Gremlin-Server (127.0.0.1:8182)... OK (connected to 127.0.0.1:8182).
Run gremlin.sh to connect.

$  bin/gremlin.sh
         \,,,/
         (o o)
-----oOOo-(3)-oOOo-----
plugin activated: tinkerpop.server
plugin activated: tinkerpop.hadoop
plugin activated: tinkerpop.utilities
plugin activated: janusgraph.imports
plugin activated: tinkerpop.tinkergraph
gremlin> :remote connect tinkerpop.server conf/remote.yaml
==>Connected - localhost/127.0.0.1:8182
gremlin> :> graph.addVertex("name", "stephen")
==>v[256]
gremlin> :> g.V().values('name')
==>stephen

JanusGraph Server must be run with a configuration for either WebSockets (for gremlin shell or other WebSocket programs) or re-configured for REST to work with REST clients.

There is, currently, no way to configure a single running instance of JanusGraph Server to communicate simultaneously with clients talking WebSockets and REST. However, it is possible to create configuration files (following the steps in this chapter) for both WebSockets and REST and start two instances of the JanusGraph Server by pointing it to the various configurations when it is started. In this way, the same JanusGraph database instance can be reached through different JanusGraph Servers through both WebSocket and REST calls. Make sure the port parameter in each yaml configuration is different if starting more than one JanusGraph Server on the same machine:

port: 8182

In the future, the option to have one running instance of JanusGraph Server supporting multiple protocols may be possible.

Since JanusGraph Server is a TinkerPop Gremlin Server packaged with configuration files for JanusGraph, a version compatible TinkerPop Gremlin Server can be downloaded separately and used with JanusGraph. Get started by downloading the appropriate version of Gremlin Server, which needs to match a version supported by the JanusGraph version in use.

	Important
	Any references to file paths in this section refer to paths under a TinkerPop distribution for Gremlin Server and not a JanusGraph distribution with the JanusGraph Server, unless specifically noted.

Configuring a standalone Gremlin Server to work with JanusGraph is similar to configuring the packaged JanusGraph Server. You should be familiar with graph configuration. Basically, the Gremlin Server yaml file points to graph-specific configuration files that are used to instantiate JanusGraph instances that it will then host. In order to instantiate these Graph instances, Gremlin Server requires that the appropriate libraries and dependencies for the JanusGraph be available on its classpath.

For purposes of demonstration, these instructions will outline how to configure the BerkeleyDB backend for JanusGraph in Gremlin Server. As stated earlier, Gremlin Server needs JanusGraph dependencies on its classpath. Invoke the following command replacing $VERSION with the version of JanusGraph to use:

bin/gremlin-server.sh -i org.janusgraph janusgraph-all $VERSION

When this process completes, Gremlin Server should now have all the JanusGraph dependencies available to it and will thus be able to instantiate JanusGraph objects.

	Important
	The above command uses Groovy Grape and if it is not configured properly download errors may ensue. Please refer to this section of the TinkerPop documentation for more information around setting up ~/.groovy/grapeConfig.xml.

Create a file called GREMLIN_SERVER_HOME/conf/janusgraph.properties with the following contents:

gremlin.graph=org.janusgraph.core.JanusGraphFactory
storage.backend=berkeleyje
storage.directory=db/berkeley

Configuration of other backends is similar. See Part III, “Storage Backends”. If using Cassandra, then use Cassandra configuration options in the janusgraph.properties file. The only important piece to leave unchanged is the gremlin.graph setting which should always use JanusGraphFactory. This setting tells Gremlin Server how to instantiate a JanusGraph instance.

Next create a file called GREMLIN_SERVER_HOME/conf/gremlin-server-janusgraph.yaml that has the following contents:

host: localhost
port: 8182
graphs: {
  graph: conf/janusgraph.properties}
plugins:
  - janusgraph.imports
scriptEngines: {
  gremlin-groovy: {
    scripts: [scripts/janusgraph.groovy]}}
serializers:
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0, config: { useMapperFromGraph: graph }}
  - { className: org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0, config: { serializeResultToString: true }}
metrics: {
  slf4jReporter: {enabled: true, interval: 180000}}

def globals = [:]
globals << [g : graph.traversal()]

The above script creates a Map called globals and assigns to it a key/value pair. The key is g and its value is a TraversalSource generated from graph, which was configured for Gremlin Server in its configuration file. At this point, there are now two global variables available to scripts provided to Gremlin Server - graph and g.

At this point, Gremlin Server is configured and can be used to connect to a new or existing JanusGraph database. To start the server:

$ bin/gremlin-server.sh conf/gremlin-server-janusgraph.yaml
[INFO] GremlinServer -
         \,,,/
         (o o)
-----oOOo-(3)-oOOo-----

[INFO] GremlinServer - Configuring Gremlin Server from conf/gremlin-server-janusgraph.yaml
[INFO] MetricManager - Configured Metrics Slf4jReporter configured with interval=180000ms and loggerName=org.apache.tinkerpop.gremlin.server.Settings$Slf4jReporterMetrics
[INFO] GraphDatabaseConfiguration - Set default timestamp provider MICRO
[INFO] GraphDatabaseConfiguration - Generated unique-instance-id=7f0000016240-ubuntu1
[INFO] Backend - Initiated backend operations thread pool of size 8
[INFO] KCVSLog$MessagePuller - Loaded unidentified ReadMarker start time 2015-10-02T12:28:24.411Z into org.janusgraph.diskstorage.log.kcvs.KCVSLog$MessagePuller@35399441
[INFO] GraphManager - Graph [graph] was successfully configured via [conf/janusgraph.properties].
[INFO] ServerGremlinExecutor - Initialized Gremlin thread pool.  Threads in pool named with pattern gremlin-*
[INFO] ScriptEngines - Loaded gremlin-groovy ScriptEngine
[INFO] GremlinExecutor - Initialized gremlin-groovy ScriptEngine with scripts/janusgraph.groovy
[INFO] ServerGremlinExecutor - Initialized GremlinExecutor and configured ScriptEngines.
[INFO] ServerGremlinExecutor - A GraphTraversalSource is now bound to [g] with graphtraversalsource[standardjanusgraph[berkeleyje:db/berkeley], standard]
[INFO] AbstractChannelizer - Configured application/vnd.gremlin-v1.0+gryo with org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0
[INFO] AbstractChannelizer - Configured application/vnd.gremlin-v1.0+gryo-stringd with org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0
[INFO] GremlinServer$1 - Gremlin Server configured with worker thread pool of 1, gremlin pool of 8 and boss thread pool of 1.
[INFO] GremlinServer$1 - Channel started at port 8182.

The following section explains how to connect to the running server.

7.4.2.1. Connecting to JanusGraph via Gremlin Server

Gremlin Server will be ready to listen for WebSocket connections when it is started. The easiest way to test the connection is with Gremlin Console.

Follow the instructions here Section 7.1.1.1, “Connecting to Gremlin Server” to verify the Gremlin Server is working.

	Important
	A difference you should understand is that when working with JanusGraph Server, the Gremlin Console is started from underneath the JanusGraph distribution and when following the test instructions here for a standalone Gremlin Server, the Gremlin Console is started from under the TinkerPop distribution.

GryoMapper mapper = GryoMapper.build().addRegistry(JanusGraphIoRegistry.INSTANCE).create();
Cluster cluster = Cluster.build().serializer(new GryoMessageSerializerV1d0(mapper)).create();
Client client = cluster.connect();
client.submit("g.V()").all().get();

By adding the JanusGraphIoRegistry to the org.apache.tinkerpop.gremlin.driver.ser.GryoMessageSerializerV1d0, the driver will know how to properly deserialize custom data types returned by JanusGraph.