hbase-client/src/main/java/org/apache/hadoop/hbase/client/Consistency.java

/**
 * 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.hbase.client;

import org.apache.yetus.audience.InterfaceAudience;

/**
 * Consistency defines the expected consistency level for an operation.
 */
@InterfaceAudience.Public
public enum Consistency {
  // developer note: Do not reorder. Client.proto#Consistency depends on this order
  /**
   * Strong consistency is the default consistency model in HBase,
   * where reads and writes go through a single server which serializes
   * the updates, and returns all data that was written and ack'd.
   */
  STRONG,

  /**
   * Timeline consistent reads might return values that may not see
   * the most recent updates. Write transactions are always performed
   * in strong consistency model in HBase which guarantees that transactions
   * are ordered, and replayed in the same order by all copies of the data.
   * In timeline consistency, the get and scan requests can be answered from data
   * that may be stale.
   * <br>
   * The client may still observe transactions out of order if the requests are
   * responded from different servers.
   */
  TIMELINE,
}