io.vlingo.lattice.grid.hashring.MurmurSortedMapHashRing Maven / Gradle / Ivy

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Tooling for reactive Domain-Driven Design projects that are highly concurrent. Includes compute grid, actor caching, spaces, cross-node cluster messaging, CQRS, and Event Sourcing support.

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package io.vlingo.lattice.grid.hashring;

import java.nio.ByteBuffer;
import java.util.SortedMap;
import java.util.TreeMap;

public class MurmurSortedMapHashRing implements HashRing {

  private static final int DefaultSeed = 31;

  private final int pointsPerNode;
  private final int seed;

  private final ByteBuffer buffer;
  private final SortedMap ring;

  public MurmurSortedMapHashRing(final int pointsPerNode) {
    this(pointsPerNode, DefaultSeed);
  }

  public MurmurSortedMapHashRing(final int pointsPerNode, final int seed) {
    this.pointsPerNode = pointsPerNode;
    this.seed = seed;
    this.buffer = ByteBuffer.allocate(64);
    this.ring = new TreeMap<>();
  }


  @Override
  public void dump() {
    System.out.println("NODES: " + ring.size());
    for (final T hashedNodePoint : ring.values()) {
      System.out.println("NODE: " + hashedNodePoint);
    }
  }

  @Override
  public HashRing includeNode(T nodeIdentifier) {
    for (int i = 0; i < pointsPerNode; i++) {
      final int hash = hashed(nodeIdentifier.toString() + i);
      ring.put(hash, nodeIdentifier);
    }
    return this;
  }

  private int hashed(final Object id) {
    buffer.clear();
    buffer.put(id.toString().getBytes());
    return MurmurHash.hash32(buffer, 0, buffer.position(), seed);
  }

  @Override
  public HashRing excludeNode(T nodeIdentifier) {
    for (int i = 0; i < pointsPerNode; i++) {
      final int hash = hashed(nodeIdentifier.toString() + i);
      ring.remove(hash);
    }
    return this;
  }

  @Override
  public T nodeOf(Object id) {
    if (ring.isEmpty()) {
      return null;
    }
    int hash = hashed(id);
    if (!ring.containsKey(hash)) {
      SortedMap tailMap =
          ring.tailMap(hash);
      hash = tailMap.isEmpty() ?
          ring.firstKey() : tailMap.firstKey();
    }
    return ring.get(hash);
  }
}