org.apache.hadoop.fs.BlockStoragePolicySpi 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.hadoop.fs;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.InterfaceStability;
/**
* A storage policy specifies the placement of block replicas on specific
* storage types.
*/
@InterfaceAudience.Public
@InterfaceStability.Stable
public interface BlockStoragePolicySpi {
/**
* Return the name of the storage policy. Policies are uniquely
* identified by name.
*
* @return the name of the storage policy.
*/
String getName();
/**
* Return the preferred storage types associated with this policy. These
* storage types are used sequentially for successive block replicas.
*
* @return preferred storage types used for placing block replicas.
*/
StorageType[] getStorageTypes();
/**
* Get the fallback storage types for creating new block replicas. Fallback
* storage types are used if the preferred storage types are not available.
*
* @return fallback storage types for new block replicas..
*/
StorageType[] getCreationFallbacks();
/**
* Get the fallback storage types for replicating existing block replicas.
* Fallback storage types are used if the preferred storage types are not
* available.
*
* @return fallback storage types for replicating existing block replicas.
*/
StorageType[] getReplicationFallbacks();
/**
* Returns true if the policy is inherit-only and cannot be changed for
* an existing file.
*
* @return true if the policy is inherit-only.
*/
boolean isCopyOnCreateFile();
}