com.dasasian.chok.client.INodeSelectionPolicy Maven / Gradle / Ivy
/**
* Copyright (C) 2014 Dasasian ([email protected])
*
* Licensed 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 com.dasasian.chok.client;
import java.util.Collection;
import java.util.List;
import java.util.Map;
/**
* Returns a Map with Nodes and shards within those nodes that have to be
* searched by the client.
*
* Since shards can be replicated over different nodes and nodes can be
* distributed in different network sections (same switch or rack, same data
* center etc.) we allow custom selection policies to implement the logic to
* make the smartest possible choice of nodes the client has to query. The node
* selection policy is also the place where an load balancing schema need to be
* implemented.
*/
public interface INodeSelectionPolicy {
/**
* During startup or as soon the client get a notification about any change in
* the grid the client calls this method with an shard-to-nodes mapping.
*
* @param shard name of the shard
* @param nodes all the nodes which serve the shard
*/
void update(String shard, Iterable nodes);
/**
* @param shard name of the shard
* @return all nodes which serves the given shard
*/
Collection getShardNodes(String shard);
/**
* If an index is undeployed, this method is called for each of it shards.
*
* @param shard name of the shard
* @return all nodes which served the shard
*/
List remove(String shard);
/**
* If a node becomes not reachable, this method is called.
*
* @param node the name of the node
*/
void removeNode(String node);
/**
* Returns a map where as key the nodeName is used and as value a list shards
* served by node we need to query. Ideally this method returns nodes with low
* latency to the client and alternate between nodes to load balance high
* traffic.
*
* @param shards the shard names
* @return the node to shards map
* @throws ShardAccessException if one of the shards could not be accessed
*/
Map> createNode2ShardsMap(Iterable shards) throws ShardAccessException;
}