| /** |
| * 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.hdfs.server.namenode; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| |
| /** |
| * Implementers of this class represent a NN resource whose availability can be |
| * checked. A resource can be either "required" or "redundant". All required |
| * resources must be available for the NN to continue operating. The NN will |
| * continue to operate as long as *any* redundant resource is available. |
| */ |
| @InterfaceAudience.Private |
| interface CheckableNameNodeResource { |
| |
| /** |
| * Is this resource currently available. |
| * |
| * @return true if and only if the resource in question is available. |
| */ |
| public boolean isResourceAvailable(); |
| |
| /** |
| * Is this resource required. |
| * |
| * @return true if and only if the resource in question is required for NN operation. |
| */ |
| public boolean isRequired(); |
| |
| } |
