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Ogre

Ogre is a Clojure Gremlin Language Variant of the Gremlin graph traversal language from Apache Tinkerpop. Like Gremlin, it can be used to query any graphs that are TinkerPop-enabled.

Project Goals

Provide an API that enhances the expressivity of Gremlin when working in Clojure.
Expose the features of TinkerPop as it makes sense in Clojure.
Don't introduce any significant amount of performance overhead.

Community

Questions related to Ogre can be asked on the clojure-titanium mailing list.

To subscribe for announcements of releases, important changes and so on, please follow @ClojureWerkz on Twitter.

Project Maturity

Despite being first released in 2014, Orge is a relatively young project that regained active development in 2016. Most of Ogre's features are driven by changes to Apache TinkerPop (specifically the Traversal API) which has largely stabilized itself in over the course of the 3.2.x line of code. As a result, Ogre tends to be fairly stable with its implementation of that API. Ogre also implements the TinkerPop Process Test Suite, which helps validate that Ogre is compliant with Gremlin.

Ogre currently targets TinkerPop 3.4.x.

Artifacts

Orge artifacts are released to Clojars. Maven users should add the following repository definition to your pom.xml:

<repository>
  <id>clojars.org</id>
  <url>http://clojars.org/repo</url>
</repository>

The Most Recent Release

With Leiningen:

[clojurewerkz/ogre "3.4.11.0"]

With Maven:

<dependency>
  <groupId>clojurewerkz</groupId>
  <artifactId>ogre</artifactId>
  <version>3.4.11.0</version>
</dependency>

Documentation & Examples

You'll need to choose a TinkerPop-enabled graph database and add that to your project's dependencies. Here we use the in-memory graph database implementation provided by org.apache.tinkerpop/tinkergraph-gremlin, e.g.:

With Leiningen:

[org.apache.tinkerpop/tinkergraph-gremlin "3.4.11"]

With Maven:

<dependency>
  <groupId>org.apache.tinkerpop</groupId>
  <artifactId>tinkergraph-gremlin</artifactId>
  <version>3.4.11</version>
</dependency>

REPL examples:

user=> (load "clojurewerkz/ogre/core")
nil
user=> (in-ns 'clojurewerkz.ogre.core)
#object[clojure.lang.Namespace 0x2bcfe59c "clojurewerkz.ogre.core"]
clojurewerkz.ogre.core=> (def graph (open-graph {(Graph/GRAPH) (.getName org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerGraph)}))
#'clojurewerkz.ogre.core/graph
clojurewerkz.ogre.core=> (def g (traversal graph))
#'clojurewerkz.ogre.core/g
clojurewerkz.ogre.core=> (org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerFactory/generateModern graph)
nil
clojurewerkz.ogre.core=> (traverse g V (match
                    #_=>   (__ (as :a) (out :created) (as :b))
                    #_=>   (__ (as :b) (has :name "lop"))
                    #_=>   (__ (as :b) (in :created) (as :c))
                    #_=>   (__ (as :c) (has :age 29)))
                    #_=>   (select :a :c) (by :name)
                    #_=>   (into-seq!))
({"a" "marko", "c" "marko"} {"a" "josh", "c" "marko"} {"a" "peter", "c" "marko"})

As an alternative to embedded graph databases like TinkerGraph, you might also choose to utilize a remote graph (e.g. one hosted in Gremlin Server or a Remote Gremlin Provider). In such case, you would first need org.apache.tinkerpop/gremlin-driver to connect to the remote graph:

With Leiningen:

[org.apache.tinkerpop/gremlin-driver "3.4.11"]

With Maven:

<dependency>
  <groupId>org.apache.tinkerpop</groupId>
  <artifactId>gremlin-driver</artifactId>
  <version>3.4.11</version>
</dependency>

From the driver, you create a DriverRemoteConnection and pass that to the traversal function (rather than the Graph instance as demonstrated in the last example):

clojurewerkz.ogre.core=> (def conn (org.apache.tinkerpop.gremlin.driver.remote.DriverRemoteConnection/using "localhost" 8182 "g"))
#'clojurewerkz.ogre.core/conn
clojurewerkz.ogre.core=> (def g (traversal conn))
#'clojurewerkz.ogre.core/g
clojurewerkz.ogre.core=> (traverse g V (has :name "josh") (values :age) (into-seq!))
(32)

In short, to connect to a remote graph simply use Java interop to construct a DriverRemoteConnection instance in the ways specified by the TinkerPop Reference Documentation and then give that object to the traversal function to create g.

Ogre has more complete documentation here.

Supported Clojure Versions

Orge requires Clojure 1.8+. The most recent stable release is always recommended.

Continuous Integration

Development

Orge uses Leiningen 2. Once installed and run tests using:

lein test

License

Licensed under the Eclipse Public License (the same as Clojure).

Acknowledgements

Joe Lee illustrated the "Gremlin Ogre" image based on the original Clojurewerkz Ogre logo and Apache TinkerPop's Gremlin character developed Ketrina Yim.