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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, 19 Mar 2018 21:37:31 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_r175576157
 
 

 ##########
 File path: server/master/src/main/java/org/apache/accumulo/master/TimeoutTaskExecutor.java
 ##########
 @@ -0,0 +1,198 @@
+/*
+ * 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.Callable;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Future;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+
+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.
+ *
+ * @param <T>
+ *          The return type for the corresponding Callable.
+ * @param <C>
+ *          The type of Callable submitted to this executor.
+ */
+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 List<WrappedTask> wrappedTasks;
+
+  private SuccessCallback<T,C> successCallback;
+  private ExceptionCallback<C> exceptionCallback;
+  private TimeoutCallback<C> timeoutCallback;
+
+  /**
+   * Constructs a new TimeoutTaskExecutor using the given executor to schedule tasks with
a max timeout. Takes an expected number of Callables to initialize the
+   * underlying task collection more appropriately.
+   *
+   * @param executorService
+   *          The executor to schedule tasks with.
+   * @param timeout
+   *          The timeout for each task.
+   * @param expectedNumCallables
+   *          The expected number of callables you will schedule (for sizing optimization).
+   */
+  public TimeoutTaskExecutor(ExecutorService executorService, long timeout, int expectedNumCallables)
{
+    this.executorService = executorService;
+    this.timeout = timeout;
+    this.wrappedTasks = new ArrayList<>(expectedNumCallables);
+  }
+
+  /**
+   * Submits a new task to the executor.
+   *
+   * @param callable
+   *          Task to run
+   */
+  public void submit(C callable) {
+    WrappedTask wt = new WrappedTask(callable, executorService.submit(callable));
+    wrappedTasks.add(wt);
+  }
+
+  /**
+   * Registers the callback to use on successful tasks.
+   *
+   * @param successCallback
+   *          The callback function to invoke on success.
+   * @throws NullPointerException
+   *           when a null successCallback is passed in
+   */
+  public void onSuccess(SuccessCallback<T,C> successCallback) {
+    this.successCallback = Objects.requireNonNull(successCallback, "Must provide a non-null
successCallback.");
+  }
+
+  /**
+   * Registers the callback to use on tasks that throw exceptions.
+   *
+   * @param exceptionCallback
+   *          The callback function to invoke on exceptions.
+   * @throws NullPointerException
+   *           when a null exceptionCallback is passed in
+   */
+  public void onException(ExceptionCallback<C> exceptionCallback) {
+    this.exceptionCallback = Objects.requireNonNull(exceptionCallback, "Must provide a non-null
exceptionCallback.");
+  }
+
+  /**
+   * Registers the callback to use on tasks that time out.
+   *
+   * @param timeoutCallback
+   *          The callback function to invoke on timeouts.
+   * @throws NullPointerException
+   *           when a null timeoutCallback is passed in
+   */
+  public void onTimeout(TimeoutCallback<C> timeoutCallback) {
+    this.timeoutCallback = Objects.requireNonNull(timeoutCallback, "Must provide a non-null
timeoutCallback.");
+  }
+
+  /**
+   * Completes all the current tasks by dispatching to the appropriated callback.
+   *
+   * @throws IllegalStateException
+   *           If all of the callbacks were not registered before calling this method.
+   * @throws InterruptedException
+   *           If interrupted while awaiting callable results.
+   */
+  public void complete() throws InterruptedException {
+    Preconditions.checkState(successCallback != null, "Must set a success callback before
completing " + this);
+    Preconditions.checkState(exceptionCallback != null, "Must set an exception callback before
completing " + this);
+    Preconditions.checkState(timeoutCallback != null, "Must set a timeout callback before
completing " + this);
+
+    for (WrappedTask wt : wrappedTasks) {
+      try {
+        successCallback.accept(wt.callable, wt.future.get(timeout, TimeUnit.MILLISECONDS));
+      } catch (InterruptedException e) {
+        throw e;
+      } catch (TimeoutException e) {
+        wt.future.cancel(true);
+        timeoutCallback.accept(wt.callable);
 
 Review comment:
   Its possible a future that is queued to execute, but has not yet executed could be canceled.
 And if this happens 3 times for a tserver, the master will try to halt it.

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