The Tinkerpop suite supports a number of graph data stores. They are all
compatible with Pacer, but I have not yet implemented the simple
adapters Pacer needs to use them yet. Here is the list of what's
supported so far:
||In-memory graph db. Included with Pacer.
||A powerful and feature rich graph / document hybrid database.
gem install --pre pacer-orient
||The industry-leading graph db.
gem install pacer-neo4j
||A very fast, relatively new graph db.
gem install pacer-dex
||Built on top of a pluggable nosql backend store
gem install pacer-titan
You can run any or all of the above graph databases. Pacer supports
running them simultaneously and even supports having many of any given
type open at once.
Out of the box, Pacer comes with only the simple in-memory TinkerGraph, an excellent graph for
testing and for temporary in-memory data. Start a TinkerGraph with:
Neo4j is the primary database used by XN Logic, the team behind Pacer. It's an excellent, reliable and performant graph database that works well
for a variety of use cases, and scales to easily support the largest data sets our customers have hit us with. Once the pacer-neo4j gem is
installed, you can start a Neo graph with:
neograph = Pacer.neo4j '/path/to/graph_dir'
As of August 2014, Pacer supports Neo4j v1.9 and v2.0. v2.1 support is in development.
(optional) Inter-operation with the neo4j gem
Pacer can work together with other Ruby GraphDB libraries, too. The
first functioning example is with theo neo4j gem. Hopefully more will
follow soon as I find out about them or get requests to support them.
To use Pacer together with the neo4j gem, get your Pacer graph instance
# start neo4j via the external gem rather than using pacer-neo4j
graph = Pacer.neo4j(Neo4j.db.graph)
After that, you can continue to use the graph as normal with both
gems. Any update that's committed with one gem will be visible
immediately to the other because they are now both pointing to the same
Java graphdb instance.
Pacer has Titan support via the
pacer-titan community contributed gem. Titan is a distributed graph database focussed on supporting extremely
large graphs. Once you've configured your project as required by the pacer-titan library, you can start a Titan graph like this:
titangraph = Pacer.titan 'path/to/titan_config.properties'
Pacer can support OrientDB and Sparksee graph databases in addition to RDF graphs and others that I may not be aware of.
The only requirement is that the graph have a Blueprints adapter. The
pacer-titan gems add graph-specific functionality on top
of Pacer's built-in capabilities, but any blueprints compatibile graph can easily be used with Pacer with minimal effort.
A note on safely exiting
Some databases need to be shutdown cleanly when the program exits. You
can shut a database down anytime by calling
graph.shutdown, but you
don't need to worry about it much. Pacer uses Ruby's
at_exit hook to
automatically shut down all open databases!