| /* |
| * 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.drill.common; |
| |
| import java.util.LinkedList; |
| import java.util.concurrent.Executor; |
| |
| /** |
| * Serializes execution of multiple submissions to a single target, while still |
| * using a thread pool to execute those submissions. Provides an implicit |
| * queueing capability for a single target that requires any commands that |
| * execute against it to be serialized. |
| */ |
| public abstract class SerializedExecutor implements Executor { |
| |
| private boolean isProcessing = false; |
| private final LinkedList<Runnable> queuedRunnables = new LinkedList<>(); |
| private final Executor underlyingExecutor; |
| private final String name; |
| |
| /** |
| * Constructor. |
| * |
| * @param underlyingExecutor |
| * underlying executor to use to execute commands submitted to this |
| * SerializedExecutor |
| */ |
| public SerializedExecutor(String name, Executor underlyingExecutor) { |
| this.underlyingExecutor = underlyingExecutor; |
| this.name = name; |
| } |
| |
| /** |
| * An exception occurred in the last command executed; this reports that to |
| * the subclass of SerializedExecutor. |
| * |
| * <p> |
| * The default implementation of this method throws an exception, which is |
| * considered an error (see below). Implementors have two alternatives: |
| * Arrange not to throw from your commands' run(), or if they do, provide an |
| * override of this method that handles any exception that is thrown. |
| * </p> |
| * |
| * <p> |
| * It is an error for this to throw an exception, and doing so will terminate |
| * the thread with an IllegalStateException. Derivers must handle any reported |
| * exceptions in other ways. |
| * </p> |
| * |
| * @param command |
| * the command that caused the exception |
| * @param t |
| * the exception |
| */ |
| protected abstract void runException(Runnable command, Throwable t); |
| |
| private class RunnableProcessor implements Runnable { |
| |
| private Runnable command; |
| |
| public RunnableProcessor(Runnable command) { |
| this.command = command; |
| } |
| |
| @Override |
| public void run() { |
| final Thread currentThread = Thread.currentThread(); |
| final String originalThreadName = currentThread.getName(); |
| currentThread.setName(name); |
| |
| try { |
| while (true) { |
| try { |
| command.run(); |
| } catch (Exception | AssertionError e) { |
| try { |
| runException(command, e); |
| } catch (Exception | AssertionError ee) { |
| throw new IllegalStateException("Exception handler threw an exception", ee); |
| } |
| } |
| synchronized (queuedRunnables) { |
| if (queuedRunnables.isEmpty()) { |
| isProcessing = false; |
| break; |
| } |
| |
| command = queuedRunnables.removeFirst(); |
| } |
| } |
| } finally { |
| currentThread.setName(originalThreadName); |
| } |
| } |
| } |
| |
| @Override |
| public void execute(Runnable command) { |
| synchronized (queuedRunnables) { |
| if (isProcessing) { |
| queuedRunnables.addLast(command); |
| return; |
| } |
| |
| isProcessing = true; |
| } |
| |
| underlyingExecutor.execute(new RunnableProcessor(command)); |
| } |
| } |