org.apache.cassandra.dht.Murmur3Partitioner Maven / Gradle / Ivy
Go to download
Show more of this group Show more artifacts with this name
Show all versions of cassandra-all Show documentation
Show all versions of cassandra-all Show documentation
A fork of the Apache Cassandra Project that uses Lucene indexes for providing near real time search such as ElasticSearch or Solr, including full text search capabilities, multi-dimensional queries, and relevance scoring.
The newest version!
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.cassandra.dht;
import java.math.BigDecimal;
import java.math.BigInteger;
import java.nio.ByteBuffer;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.apache.cassandra.db.BufferDecoratedKey;
import org.apache.cassandra.db.DecoratedKey;
import org.apache.cassandra.db.marshal.AbstractType;
import org.apache.cassandra.db.marshal.LongType;
import org.apache.cassandra.exceptions.ConfigurationException;
import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.cassandra.utils.FBUtilities;
import org.apache.cassandra.utils.MurmurHash;
import org.apache.cassandra.utils.ObjectSizes;
/**
* This class generates a BigIntegerToken using a Murmur3 hash.
*/
public class Murmur3Partitioner extends AbstractPartitioner
{
public static final LongToken MINIMUM = new LongToken(Long.MIN_VALUE);
public static final long MAXIMUM = Long.MAX_VALUE;
private static final int HEAP_SIZE = (int) ObjectSizes.measureDeep(MINIMUM);
public DecoratedKey decorateKey(ByteBuffer key)
{
return new BufferDecoratedKey(getToken(key), key);
}
public Token midpoint(Token lToken, Token rToken)
{
// using BigInteger to avoid long overflow in intermediate operations
BigInteger l = BigInteger.valueOf(((LongToken) lToken).token),
r = BigInteger.valueOf(((LongToken) rToken).token),
midpoint;
if (l.compareTo(r) < 0)
{
BigInteger sum = l.add(r);
midpoint = sum.shiftRight(1);
}
else // wrapping case
{
BigInteger max = BigInteger.valueOf(MAXIMUM);
BigInteger min = BigInteger.valueOf(MINIMUM.token);
// length of range we're bisecting is (R - min) + (max - L)
// so we add that to L giving
// L + ((R - min) + (max - L) / 2) = (L + R + max - min) / 2
midpoint = (max.subtract(min).add(l).add(r)).shiftRight(1);
if (midpoint.compareTo(max) > 0)
midpoint = min.add(midpoint.subtract(max));
}
return new LongToken(midpoint.longValue());
}
public LongToken getMinimumToken()
{
return MINIMUM;
}
/**
* Generate the token of a key.
* Note that we need to ensure all generated token are strictly bigger than MINIMUM.
* In particular we don't want MINIMUM to correspond to any key because the range (MINIMUM, X] doesn't
* include MINIMUM but we use such range to select all data whose token is smaller than X.
*/
public LongToken getToken(ByteBuffer key)
{
if (key.remaining() == 0)
return MINIMUM;
long[] hash = new long[2];
MurmurHash.hash3_x64_128(key, key.position(), key.remaining(), 0, hash);
return new LongToken(normalize(hash[0]));
}
public long getHeapSizeOf(LongToken token)
{
return HEAP_SIZE;
}
public LongToken getRandomToken()
{
return new LongToken(normalize(FBUtilities.threadLocalRandom().nextLong()));
}
private long normalize(long v)
{
// We exclude the MINIMUM value; see getToken()
return v == Long.MIN_VALUE ? Long.MAX_VALUE : v;
}
public boolean preservesOrder()
{
return false;
}
public Map describeOwnership(List sortedTokens)
{
Map ownerships = new HashMap();
Iterator i = sortedTokens.iterator();
// 0-case
if (!i.hasNext())
throw new RuntimeException("No nodes present in the cluster. Has this node finished starting up?");
// 1-case
if (sortedTokens.size() == 1)
ownerships.put((Token) i.next(), new Float(1.0));
// n-case
else
{
final BigInteger ri = BigInteger.valueOf(MAXIMUM).subtract(BigInteger.valueOf(MINIMUM.token + 1)); // (used for addition later)
final BigDecimal r = new BigDecimal(ri);
Token start = (Token) i.next();BigInteger ti = BigInteger.valueOf(((LongToken)start).token); // The first token and its value
Token t; BigInteger tim1 = ti; // The last token and its value (after loop)
while (i.hasNext())
{
t = (Token) i.next(); ti = BigInteger.valueOf(((LongToken) t).token); // The next token and its value
float age = new BigDecimal(ti.subtract(tim1).add(ri).mod(ri)).divide(r, 6, BigDecimal.ROUND_HALF_EVEN).floatValue(); // %age = ((T(i) - T(i-1) + R) % R) / R
ownerships.put(t, age); // save (T(i) -> %age)
tim1 = ti; // -> advance loop
}
// The start token's range extends backward to the last token, which is why both were saved above.
float x = new BigDecimal(BigInteger.valueOf(((LongToken)start).token).subtract(ti).add(ri).mod(ri)).divide(r, 6, BigDecimal.ROUND_HALF_EVEN).floatValue();
ownerships.put(start, x);
}
return ownerships;
}
public Token.TokenFactory getTokenFactory()
{
return tokenFactory;
}
private final Token.TokenFactory tokenFactory = new Token.TokenFactory()
{
public ByteBuffer toByteArray(Token longToken)
{
return ByteBufferUtil.bytes(longToken.token);
}
public Token fromByteArray(ByteBuffer bytes)
{
return new LongToken(ByteBufferUtil.toLong(bytes));
}
public String toString(Token longToken)
{
return longToken.token.toString();
}
public void validate(String token) throws ConfigurationException
{
try
{
Long i = Long.valueOf(token);
}
catch (NumberFormatException e)
{
throw new ConfigurationException(e.getMessage());
}
}
public Token fromString(String string)
{
try
{
return new LongToken(Long.valueOf(string));
}
catch (NumberFormatException e)
{
throw new IllegalArgumentException(String.format("Invalid token for Murmur3Partitioner. Got %s but expected a long value (unsigned 8 bytes integer).", string));
}
}
};
public AbstractType getTokenValidator()
{
return LongType.instance;
}
}