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 com.datastax.oss.driver.internal.core.time;
  
  import com.datastax.oss.driver.api.core.context.DriverContext;
  import com.datastax.oss.driver.internal.core.context.InternalDriverContext;
  import com.datastax.oss.driver.shaded.guava.common.annotations.VisibleForTesting;
  import java.util.concurrent.atomic.AtomicLong;
  import net.jcip.annotations.ThreadSafe;
  
  /**
   * A timestamp generator that guarantees monotonically increasing timestamps across all client
   * threads, and logs warnings when timestamps drift in the future.
   *
   * <p>To activate this generator, modify the {@code advanced.timestamp-generator} section in the
   * driver configuration, for example:
   *
   * <pre>
   * datastax-java-driver {
   *   advanced.timestamp-generator {
   *     class = AtomicTimestampGenerator
   *     drift-warning {
   *       threshold = 1 second
   *       interval = 10 seconds
   *     }
   *     force-java-clock = false
   *   }
   * }
   * </pre>
   *
   * See {@code reference.conf} (in the manual or core driver JAR) for more details.
   */
  @ThreadSafe
  public class AtomicTimestampGenerator extends MonotonicTimestampGenerator {
  
    private final AtomicLong lastRef = new AtomicLong(0);
  
    public AtomicTimestampGenerator(DriverContext context) {
      super(context);
    }
  
    @VisibleForTesting
    AtomicTimestampGenerator(Clock clock, InternalDriverContext context) {
      super(clock, context);
    }
  
    @Override
    public long next() {
      while (true) {
        long last = lastRef.get();
        long next = computeNext(last);
        if (lastRef.compareAndSet(last, next)) {
          return next;
        }
      }
    }
  }
  