This is an implementation of the TinkerPop Blueprints 2.6 API using Apache Accumulo as the backend. This combines the many benefits and flexibility of Blueprints with the scalability and performance of Accumulo.
In addition to the basic Blueprints functionality, we provide a number of enhanced features, including:
Feel free to contact us with bugs, suggestions, pull requests, or simply how you are leveraging AccumuloGraph in your own work.
First, include AccumuloGraph as a Maven dependency. Releases are deployed to Maven Central.
<dependency> <groupId>edu.jhuapl.tinkerpop</groupId> <artifactId>blueprints-accumulo-graph</artifactId> <version>0.2.1</version> </dependency>
For non-Maven users, the binary jars can be found in the releases section in this GitHub repository, or you can get them from Maven Central.
AccumuloGraph involves setting a few parameters in an
AccumuloGraphConfiguration object, and opening the graph.
The defaults are sensible for using an Accumulo cluster.
We provide some simple examples below. Javadocs for
AccumuloGraphConfiguration explain all the other parameters
in more detail.
First, to instantiate an in-memory graph:
Configuration cfg = new AccumuloGraphConfiguration() .setInstanceType(InstanceType.Mock) .setGraphName("graph"); return GraphFactory.open(cfg);
This creates a "Mock" instance which holds the graph in memory. You can now use all the Blueprints and AccumuloGraph-specific functionality with this in-memory graph. This is useful for getting familiar with AccumuloGraph's functionality, or for testing or prototyping purposes.
To use an actual Accumulo cluster, use the following:
Configuration cfg = new AccumuloGraphConfiguration() .setInstanceType(InstanceType.Distributed) .setZooKeeperHosts("zookeeper-host") .setInstanceName("instance-name") .setUser("user").setPassword("password") .setGraphName("graph") .setCreate(true); return GraphFactory.open(cfg);
This directs AccumuloGraph to use a "Distributed" Accumulo
instance, and sets the appropriate ZooKeeper parameters,
instance name, and authentication information, which correspond
to the usual Accumulo connection settings. The graph name is
used to create several backing tables in Accumulo, and the
setCreate option tells AccumuloGraph to create the backing
tables if they don't already exist.
AccumuloGraph also has limited support for a "Mini" instance of Accumulo.
This section describes various configuration parameters that
greatly enhance AccumuloGraph's performance. Brief descriptions
of each option are provided here, but refer to the
AccumuloGraphConfiguration Javadoc for fuller explanations.
The Blueprints API specifies a number of consistency checks for various operations, and requires errors if they fail. Some examples of invalid operations include adding a vertex with the same id as an existing vertex, adding edges between nonexistent vertices, and setting properties on nonexistent elements. Unfortunately, checking the above constraints for an Accumulo installation entails significant performance issues, since these require extra traffic to Accumulo using inefficient non-batched access patterns.
To remedy these performance issues, AccumuloGraph exposes several options to disable various of the above checks. These include:
setAutoFlush- to disable automatically flushing changes to the backing Accumulo tables
setSkipExistenceChecks- to disable element existence checks, avoiding trips to the Accumulo cluster
setIndexableGraphDisabled- to disable indexing functionality, which improves performance of element removal
Accumulo itself features a number of performance-related parameters, and we allow configuration of these. Generally, these relate to write buffer sizes, multithreading, etc. The settings include:
setMaxWriteLatency- max time prior to flushing element write buffer
setMaxWriteMemory- max size for element write buffer
setMaxWriteThreads- max threads used for element writing
setMaxWriteTimeout- max time to wait before failing element buffer writes
setQueryThreads- number of query threads to use for fetching elements, properties etc.
As a performance tweak, AccumuloGraph performs lazy loading of
properties and edges. This means that an operation such as
getVertex does not by default populate the returned
vertex object with the associated vertex's properties
and edges. Instead, they are initialized only when requested via
getEdges, etc. These are useful
for use cases where you won't be accessing many of these
properties. However, if certain properties or edges will
be accessed frequently, you can set options for preloading
these specific properties and edges, which will be more
efficient than on-the-fly loading. These options include:
setPreloadedProperties- set property keys to be preloaded
setPreloadedEdgeLabels- set edges to be preloaded based on their labels
AccumuloGraph contains a number of caching options that mitigate the need for Accumulo traffic for recently-accessed elements. The following options control caching:
setVertexCacheParams- size and expiry for vertex cache
setEdgeCacheParams- size and expiry for edge cache
setPropertyCacheTimeout- property expiry time, which can be specified globally and/or for individual properties
One of Accumulo's key advantages is its ability for high-speed ingest
of huge amounts of data. To leverage this ability, we provide
AccumuloBulkIngester class that
exchanges consistency guarantees for high speed ingest.
The following is an example of how to use the bulk ingester to ingest a simple graph:
AccumuloGraphConfiguration cfg = ...; AccumuloBulkIngester ingester = new AccumuloBulkIngester(cfg); // Add a vertex. ingester.addVertex("A").finish(); // Add another vertex with properties. ingester.addVertex("B") .add("P1", "V1").add("P2", "V2") .finish(); // Add an edge. ingester.addEdge("A", "B", "edge").finish(); // Shutdown and compact tables. ingester.shutdown(true);
See the Javadocs for more details. Note that you are responsible for ensuring that data is entered in a consistent way, or the resulting graph will have undefined behavior.
AccumuloGraph features Hadoop integration via custom input and output
allow vertex and edge inputs to mappers, respectively. Use as follows:
AccumuloGraphConfiguration cfg = ...; // For vertices: Job j = new Job(); j.setInputFormatClass(VertexInputFormat.class); VertexInputFormat.setAccumuloGraphConfiguration(j, cfg); // For edges: Job j = new Job(); j.setInputFormatClass(EdgeInputFormat.class); EdgeInputFormat.setAccumuloGraphConfiguration(j, cfg);
ElementOutputFormat allows writing to an AccumuloGraph from
reducers. Use as follows:
AccumuloGraphConfiguration cfg = ...; Job j = new Job(); j.setOutputFormatClass(ElementOutputFormat.class); ElementOutputFormat.setAccumuloGraphConfiguration(j, cfg);
Below is a snippet to show an example of AccumuloGraph integration with Rexster. For a complete list of options for configuration, see
<graph> <graph-enabled>true</graph-enabled> <graph-name>myGraph</graph-name> <graph-type>edu.jhuapl.tinkerpop.AccumuloRexsterGraphConfiguration</graph-type> <properties> <blueprints.accumulo.instance.type>Distributed</blueprints.accumulo.instance.type> <blueprints.accumulo.instance>accumulo</blueprints.accumulo.instance> <blueprints.accumulo.zkhosts>zk1,zk2,zk3</blueprints.accumulo.zkhosts> <blueprints.accumulo.user>user</blueprints.accumulo.user> <blueprints.accumulo.password>password</blueprints.accumulo.password> </properties> <extensions> </extensions> </graph>