com.datatorrent.api.StorageAgent 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 com.datatorrent.api;
import java.io.IOException;
/**
* Interface to define writing/reading checkpoint state of any operator.
*
* @since 0.9.4
*/
public interface StorageAgent
{
/**
* Save the object so that the same object can be loaded later using the given combination of
* operatorId and windowId.
*
* Typically the storage agent would serialize the state of the object during the save state.
* The serialized state can be accessed from anywhere on the cluster to recreate the object
* through the load callback.
*
* @param object - The operator whose state needs to be saved.
* @param operatorId - Identifier of the operator.
* @param windowId - Identifier for the specific state of the operator.
* @throws IOException
*/
public void save(Object object, int operatorId, long windowId) throws IOException;
/**
* Get the input stream from which can be used to retrieve the stored objects back.
*
* @param operatorId Id for which the object was previously saved
* @param windowId WindowId for which the object was previously saved
* @return object (or a copy of it) which was saved earlier using the save call.
* @throws IOException
*/
public Object load(int operatorId, long windowId) throws IOException;
/**
* Delete the artifacts related to store call of the operatorId and the windowId.
*
* Through this call, the agent is informed that the object saved against the operatorId
* and the windowId together will not be needed again.
*
* @param operatorId
* @param windowId
* @throws IOException
*/
public void delete(int operatorId, long windowId) throws IOException;
/**
* Return an array windowId for which the object was saved but not deleted.
*
* The set is essentially difference between two sets. The first set contains
* all the windowIds passed using the successful save calls. The second set contains all
* the windowIds passed using the successful delete calls.
*
* @param operatorId - The operator for which the state was saved.
* @return Collection of windowIds for available states that can be retrieved through load.
* @throws IOException
*/
public long[] getWindowIds(int operatorId) throws IOException;
}