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.api.core.specex;
  
  import com.datastax.oss.driver.api.core.CqlIdentifier;
  import com.datastax.oss.driver.api.core.metadata.Node;
  import com.datastax.oss.driver.api.core.session.Request;
  import com.datastax.oss.driver.api.core.session.SessionBuilder;
  import edu.umd.cs.findbugs.annotations.NonNull;
  import edu.umd.cs.findbugs.annotations.Nullable;
  
  /**
   * The policy that decides if the driver will send speculative queries to the next nodes when the
   * current node takes too long to respond.
   */
  public interface SpeculativeExecutionPolicy extends AutoCloseable {
  
    /**
     * @param node the node that caused the speculative execution (that is, the node that was queried
     *     previously but was too slow to answer)
     * @param keyspace the CQL keyspace currently associated to the session. This is set either
     *     through the configuration, by calling {@link SessionBuilder#withKeyspace(CqlIdentifier)},
     *     or by manually executing a {@code USE} CQL statement. It can be {@code null} if the session
     *     has no keyspace.
     * @param request the request to execute.
     * @param runningExecutions the number of executions that are already running (including the
     *     initial, non-speculative request). For example, if this is 2 it means the initial attempt
     *     was sent, then the driver scheduled a first speculative execution, and it is now asking for
     *     the delay until the second speculative execution.
     * @return the time (in milliseconds) until a speculative request is sent to the next node, or 0
     *     to send it immediately, or a negative value to stop sending requests.
     */
    long nextExecution(
        @NonNull Node node,
        @Nullable CqlIdentifier keyspace,
        @NonNull Request request,
        int runningExecutions);
  
    /** Called when the cluster that this policy is associated with closes. */
    @Override
    void close();
  }
  