content: /*
   * 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.bookkeeper.statelib.api;
  
  import org.apache.bookkeeper.common.annotation.InterfaceAudience.Public;
  import org.apache.bookkeeper.common.annotation.InterfaceStability.Evolving;
  import org.apache.bookkeeper.statelib.api.exceptions.StateStoreException;
  
  /**
   * A store that holds the states for stateful applications. Those stateful applications
   * can be databases, metadata services or stream processors.
   *
   * <p>This interface only specifies the basic functionality for saving and restoring state,
   * and its lifecycle management. Other capabilities are deferred to stateful applications.
   */
  @Public
  @Evolving
  public interface StateStore extends AutoCloseable {
  
      /**
       * Returns the name of the state store.
       *
       * @return the name of the state store.
       */
      String name();
  
      /**
       * Initialize the state store.
       */
      void init(StateStoreSpec spec) throws StateStoreException;
  
      /**
       * Provides a mechanism to checkpoint the local state store to a remote checkpoint store specified
       * at {@link StateStoreSpec#getCheckpointStore()}.
       */
      default void checkpoint() {
      }
  
      /**
       * Get the last revision of the updates applied to this state store.
       *
       * @return last revision of the updates applied to this state store.
       */
      long getLastRevision();
  
      /**
       * Flush the state store to persistent medium.
       *
       * <p>Upon the call is returned, the state store should be durably persisted.</p>
       */
      void flush() throws StateStoreException;
  
      /**
       * Close the state store.
       */
      @Override
      void close();
  
  }
  