org.apache.storm.cassandra

Class Murmur3StreamGrouping

java.lang.Object

org.apache.storm.cassandra.Murmur3StreamGrouping

All Implemented Interfaces:

Serializable, CustomStreamGrouping

public class Murmur3StreamGrouping
extends Object
implements CustomStreamGrouping

Simple CustomStreamGrouping that uses Murmur3 algorithm to choose the target task of a tuple.

This stream grouping may be used to optimise writes to Apache Cassandra.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
Murmur3StreamGrouping(List<String> partitionKeyNames) Creates a new Murmur3StreamGrouping instance.
Murmur3StreamGrouping(String... partitionKeyNames) Creates a new Murmur3StreamGrouping instance.

Method Summary

Modifier and Type	Method and Description
List<Integer>	chooseTasks(int taskId, List<Object> values) This function implements a custom stream grouping.
static long	hashes(List<Object> values) Computes the murmur3 hash for the specified values.
void	prepare(WorkerTopologyContext context, GlobalStreamId stream, List<Integer> targetTasks) Tells the stream grouping at runtime the tasks in the target bolt.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Murmur3StreamGrouping

public Murmur3StreamGrouping(String... partitionKeyNames)

Creates a new Murmur3StreamGrouping instance.

Parameters:

partitionKeyNames - partitionKeyNames.

Murmur3StreamGrouping

public Murmur3StreamGrouping(List<String> partitionKeyNames)

Creates a new Murmur3StreamGrouping instance.

Parameters:

partitionKeyNames - partitionKeyNames.

Method Detail

hashes

public static long hashes(List<Object> values)
                   throws IOException

Computes the murmur3 hash for the specified values. http://stackoverflow.com/questions/27212797/cassandra-hashing-algorithm-with-composite-keys https://github.com/apache/cassandra/blob/trunk/src/java/org/apache/cassandra/db/marshal/CompositeType.java

Parameters:

values - the fields which are part of the (compose) partition key

Returns:

the computed hash for input values

Throws:

IOException

prepare

public void prepare(WorkerTopologyContext context,
                    GlobalStreamId stream,
                    List<Integer> targetTasks)

Tells the stream grouping at runtime the tasks in the target bolt. This information should be used in chooseTasks to determine the target tasks.

It also tells the grouping the metadata on the stream this grouping will be used on.

Specified by:

prepare in interface CustomStreamGrouping

chooseTasks

public List<Integer> chooseTasks(int taskId,
                                 List<Object> values)

This function implements a custom stream grouping. It takes in as input the number of tasks in the target bolt in prepare and returns the tasks to send the tuples to.

Specified by:

chooseTasks in interface CustomStreamGrouping

values - the values to group on