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.cassandra.service.reads;
  
  import org.apache.cassandra.exceptions.ConfigurationException;
  import org.apache.cassandra.metrics.SnapshottingTimer;
  import org.apache.cassandra.schema.TableParams;
  
  public interface SpeculativeRetryPolicy
  {
      public enum Kind
      {
          NEVER, FIXED, PERCENTILE, HYBRID, ALWAYS
      }
  
      /**
       * Calculate the delay in microseconds after which speculation takes place
       *
       * @param latency       snapshot of coordinator latencies (in microseconds)
       * @param existingValue existing speculation threshold (in microseconds)
       * @return speculation delay (in microseconds).
       */
      long calculateThreshold(SnapshottingTimer latency, long existingValue);
  
      Kind kind();
  
      public static SpeculativeRetryPolicy fromString(String str)
      {
          if (AlwaysSpeculativeRetryPolicy.stringMatches(str))
              return AlwaysSpeculativeRetryPolicy.INSTANCE;
  
          if (NeverSpeculativeRetryPolicy.stringMatches(str))
              return NeverSpeculativeRetryPolicy.INSTANCE;
  
          if (PercentileSpeculativeRetryPolicy.stringMatches(str))
              return PercentileSpeculativeRetryPolicy.fromString(str);
  
          if (FixedSpeculativeRetryPolicy.stringMatches(str))
              return FixedSpeculativeRetryPolicy.fromString(str);
  
          if (HybridSpeculativeRetryPolicy.stringMatches(str))
              return HybridSpeculativeRetryPolicy.fromString(str);
  
          throw new ConfigurationException(String.format("Invalid value %s for option '%s'", str, TableParams.Option.SPECULATIVE_RETRY));
      }
  }
  