| /** |
| * 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. |
| */ |
| |
| /** |
| * The federation state store tracks persistent values that are shared between |
| * multiple routers. |
| * <p> |
| * Data is stored in data records that inherit from a common class. Data records |
| * are serialized when written to the data store using a modular serialization |
| * implementation. The default is profobuf serialization. Data is stored as rows |
| * of records of the same type with each data member in a record representing a |
| * column. |
| * <p> |
| * The state store uses a modular data storage |
| * {@link org.apache.hadoop.hdfs.server.federation.store.driver.StateStoreDriver |
| * StateStoreDriver} to handle querying, updating and deleting data records. The |
| * data storage driver is initialized and maintained by the |
| * {@link org.apache.hadoop.hdfs.server.federation.store. |
| * StateStoreService FederationStateStoreService}. The state store |
| * supports fetching all records of a type, filtering by column values or |
| * fetching a single record by its primary key. |
| * <p> |
| * The state store contains several API interfaces, one for each data records |
| * type. |
| * <p> |
| * <ul> |
| * <li>FederationMembershipStateStore: state of all Namenodes in the federation. |
| * Uses the MembershipState record. |
| * <li>FederationMountTableStore: Mount table mapping paths in the global |
| * namespace to individual subcluster paths. Uses the MountTable record. |
| * <li>RouterStateStore: State of all routers in the federation. Uses the |
| * RouterState record. |
| * </ul> |
| * <p> |
| * Each API is defined in a separate interface. The implementations of these |
| * interfaces are responsible for accessing the |
| * {@link org.apache.hadoop.hdfs.server.federation.store.driver.StateStoreDriver |
| * StateStoreDriver} to query, update and delete data records. |
| */ |
| |
| @InterfaceAudience.Private |
| @InterfaceStability.Evolving |
| |
| package org.apache.hadoop.hdfs.server.federation.store; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
