net.spy.memcached.util.DefaultKetamaNodeLocatorConfiguration Maven / Gradle / Ivy
The newest version!
package net.spy.memcached.util;
import java.util.HashMap;
import java.util.Map;
import net.spy.memcached.MemcachedNode;
/**
* A Default implementation of the configuration required for the
* KetamaNodeLocator algorithm to run.
*/
public class DefaultKetamaNodeLocatorConfiguration implements
KetamaNodeLocatorConfiguration {
private static final int NUM_REPS = 160;
// Internal lookup map to try to carry forward the optimisation that was
// previously in KetamaNodeLocator
protected Map socketAddresses =
new HashMap();
/**
* Returns the socket address of a given MemcachedNode.
*
* @param node The node which we're interested in
* @return String the socket address of that node.
*/
protected String getSocketAddressForNode(MemcachedNode node) {
// Using the internal map retrieve the socket addresses
// for given nodes.
// I'm aware that this code is inherently thread-unsafe as
// I'm using a HashMap implementation of the map, but the worst
// case ( I believe) is we're slightly in-efficient when
// a node has never been seen before concurrently on two different
// threads, so it the socketaddress will be requested multiple times!
// all other cases should be as fast as possible.
String result = socketAddresses.get(node);
if (result == null) {
result = String.valueOf(node.getSocketAddress());
result = result.substring(result.indexOf('/') + 1);
socketAddresses.put(node, result);
}
return result;
}
/**
* Returns the number of discrete hashes that should be defined for each
* node in the continuum.
*
* @return NUM_REPS repetitions.
*/
public int getNodeRepetitions() {
return NUM_REPS;
}
/**
* Returns a uniquely identifying key, suitable for hashing by the
* KetamaNodeLocator algorithm.
*
*
* This default implementation uses the socket-address of the MemcachedNode
* and concatenates it with a hyphen directly against the repetition number
* for example a key for a particular server's first repetition may look
* like:
*
*
*
* myhost/10.0.2.1-0
*
*
* for the second repetition
*
* myhost/10.0.2.1-1
*
*
* for a server where reverse lookups are failing the returned keys
* may look like
*
*
*
* /10.0.2.1-0 and /10.0.2.1-1
*
*
* @param node The MemcachedNode to use to form the unique identifier
* @param repetition The repetition number for the particular node in
* question (0 is the first repetition)
* @return The key that represents the specific repetition of the
* node
*/
public String getKeyForNode(MemcachedNode node, int repetition) {
return getSocketAddressForNode(node) + "-" + repetition;
}
}