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.bookie.datainteg;
  
  import java.io.IOException;
  import java.util.concurrent.CompletableFuture;
  
  /**
   * The interface for the data integrity check feature. This feature allows
   * a bookie to handle data loss scenarios such as when running without
   * the journal or after a disk failure has caused the loss of all data.
   */
  public interface DataIntegrityCheck {
      /**
       * Run quick preboot check. This check should do enough to ensure that
       * it is safe to complete the boot sequence without compromising correctness.
       * To this end, if it finds that this bookie is part of the last ensemble of
       * an unclosed ledger, it must prevent the bookie from being able store new
       * entries for that ledger and must prevent the bookie from taking part in
       * the discovery of the last entry of that ledger.
       */
      CompletableFuture<Void> runPreBootCheck(String reason);
  
      /**
       * Whether we need to run a full check.
       * This condition can be set by the runPreBoot() call to run a full check
       * in the background once the bookie is running. This can later be used
       * to run the full check periodically, or to exponentially backoff and retry
       * when some transient condition prevents a ledger being fixed during a
       * full check.
       */
      boolean needsFullCheck() throws IOException;
  
      /**
       * Run full check of bookies local data. This check should ensure that
       * if the metadata service states that it should have an entry, then it
       * should have that entry. If the entry is missing, it should copy it
       * from another available source.
       */
      CompletableFuture<Void> runFullCheck();
  }
  