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Subject [GitHub] keith-turner commented on a change in pull request #402: ACCUMULO-4615: Updated get status for thread safety and with a per-task timeout
Date Mon, 26 Mar 2018 17:03:39 GMT
keith-turner commented on a change in pull request #402: ACCUMULO-4615: Updated get status
for thread safety and with a per-task timeout
URL: https://github.com/apache/accumulo/pull/402#discussion_r177163927
 
 

 ##########
 File path: server/master/src/main/java/org/apache/accumulo/master/TimeoutTaskExecutor.java
 ##########
 @@ -0,0 +1,235 @@
+/*
+ * 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.accumulo.master;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Objects;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.BlockingQueue;
+import java.util.concurrent.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+import javax.annotation.concurrent.NotThreadSafe;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import com.google.common.base.Preconditions;
+
+/**
+ * Runs one or more tasks with a timeout per task (instead of a timeout for the entire pool).
Uses callbacks to invoke functions on successful, timed out, or
+ * tasks that error.
+ *
+ * This class uses an underlying fixed thread pool to schedule the submitted tasks. Once
a task is submitted, the desired end time for the task is recorded and
+ * used to determine the timeout for the task's associated {@link Future}.
+ *
+ * The timeout will not be exact as the start time is recorded prior to submitting the {@link
Callable}. This may result in an effective timeout that is
+ * slightly smaller than expected. The timeout used during initialization should be adjusted
accordingly.
+ *
+ * The {@link TimeoutTaskExecutor} itself is not a thread-safe class. Only a single thread
should submit tasks and complete them.
+ *
+ * @param <T> The return type for the corresponding Callable.
+ * @param <C> The type of Callable submitted to this executor.
+ */
+@NotThreadSafe
+public class TimeoutTaskExecutor<T, C extends Callable<T>> implements AutoCloseable
{
+
+  private final static Logger log = LoggerFactory.getLogger(TimeoutTaskExecutor.class);
+
+  private final long timeout;
+  private final ExecutorService executorService;
+  private final BlockingQueue<WrappedTask> startedTasks;
 
 Review comment:
   I like how you solved the busy wait problem by adding this queue.

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