/*
 * 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.concurrent;

import org.apache.cassandra.service.ClientWarn;
import org.apache.cassandra.tracing.Tracing;

public interface ExecutorLocal<T>
{
    ExecutorLocal[] all = { Tracing.instance, ClientWarn.instance };

    
This is called when scheduling the task, and also before calling set(Object) when running on a executor thread. 
Returns:
The thread-local value that we want to copy across executor boundaries; may be null if not set./**
     * This is called when scheduling the task, and also before calling {@link #set(Object)} when running on a
     * executor thread.
     *
     * @return The thread-local value that we want to copy across executor boundaries; may be null if not set.
     */
    T get();

    
Before a task has been run, this will be called with the value from the thread that scheduled the task, and after
the task is finished, the value that was previously retrieved from this thread is restored.
Params:
value – Value to use for the executor local state; may be null./**
     * Before a task has been run, this will be called with the value from the thread that scheduled the task, and after
     * the task is finished, the value that was previously retrieved from this thread is restored.
     *
     * @param value Value to use for the executor local state; may be null.
     */
    void set(T value);
}