org.apache.distributedlog.service.placement.PlacementStateManager Maven / Gradle / Ivy
/**
* 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.distributedlog.service.placement;
import java.util.TreeSet;
/**
* The PlacementStateManager handles persistence of calculated resource placements.
*/
public interface PlacementStateManager {
/**
* Saves the ownership mapping as a TreeSet of ServerLoads to persistent storage.
*/
void saveOwnership(TreeSet serverLoads) throws StateManagerSaveException;
/**
* Loads the ownership mapping as TreeSet of ServerLoads from persistent storage.
*/
TreeSet loadOwnership() throws StateManagerLoadException;
/**
* Watch the persistent storage for changes to the ownership mapping.
*
* The placementCallback callbacks will be triggered with the new mapping when a change occurs.
*/
void watch(PlacementCallback placementCallback);
/**
* Placement Callback.
*
*
The callback is triggered when server loads are updated.
*/
interface PlacementCallback {
void callback(TreeSet serverLoads);
}
/**
* The base exception thrown when state manager encounters errors.
*/
abstract class StateManagerException extends Exception {
public StateManagerException(String message, Exception e) {
super(message, e);
}
}
/**
* Exception thrown when failed to load the ownership mapping.
*/
class StateManagerLoadException extends StateManagerException {
public StateManagerLoadException(Exception e) {
super("Load of Ownership failed", e);
}
}
/**
* Exception thrown when failed to save the ownership mapping.
*/
class StateManagerSaveException extends StateManagerException {
public StateManagerSaveException(Exception e) {
super("Save of Ownership failed", e);
}
}
}