Package org.apache.cassandra.dht

Class RangeFetchMapCalculator

java.lang.Object

org.apache.cassandra.dht.RangeFetchMapCalculator

public class RangeFetchMapCalculator
extends java.lang.Object

We model the graph like this: * Each range we are about to stream is a vertex in the graph * Each node that can provide a range is a vertex in the graph * We add an edge from each range to the node that can provide the range * Then, to be able to solve the maximum flow problem using Ford-Fulkerson we add a super source with edges to all range vertices and a super sink with incoming edges from all the node vertices. * The capacity on the edges between the super source and the range-vertices is 1 * The capacity on the edges between the range-vertices and the node vertices is infinite * The capacity on the edges between the nodes-vertices and the super sink is ceil(#range-vertices/#node-vertices) - if we have more machines than ranges to stream the capacity will be 1 (each machine will stream at most 1 range) * Since the sum of the capacity on the edges from the super source to the range-vertices is less or equal to the sum of the capacities between the node-vertices and super sink we know that to get maximum flow we will use all the range-vertices. (Say we have x ranges, y machines to provide them, total supersource -> range-vertice capacity will be x, total node-vertice -> supersink capacity will be (y * ceil(x / y)) which worst case is x if x==y). The capacity between the range-vertices and node-vertices is infinite. * Then we try to solve the max-flow problem using psjava * If we can't find a solution where the total flow is = number of range-vertices, we bump the capacity between the node-vertices and the super source and try again.

Constructor Summary

Constructors

Constructor	Description
RangeFetchMapCalculator(EndpointsByRange rangesWithSources, java.util.Collection<RangeStreamer.SourceFilter> sourceFilters, java.lang.String keyspace)

Method Summary

Modifier and Type	Method	Description
com.google.common.collect.Multimap<InetAddressAndPort,Range<Token>>	getRangeFetchMap()

Methods inherited from class java.lang.Object

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

Constructor Detail

RangeFetchMapCalculator

public RangeFetchMapCalculator(EndpointsByRange rangesWithSources,
                               java.util.Collection<RangeStreamer.SourceFilter> sourceFilters,
                               java.lang.String keyspace)

Method Detail

getRangeFetchMap

public com.google.common.collect.Multimap<InetAddressAndPort,Range<Token>> getRangeFetchMap()