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Date: Mon, 7 Nov 2016 20:20:58 +0000 (UTC)
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Subject: [jira] [Commented] (HDFS-11114) Support for running async disk
 checks in DataNode
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archived-at: Mon, 07 Nov 2016 20:21:01 -0000


    [ https://issues.apache.org/jira/browse/HDFS-11114?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15645304#comment-15645304 ] 

ASF GitHub Bot commented on HDFS-11114:
---------------------------------------

Github user anuengineer commented on a diff in the pull request:

    https://github.com/apache/hadoop/pull/153#discussion_r86860005
  
    --- Diff: hadoop-hdfs-project/hadoop-hdfs/src/main/java/org/apache/hadoop/hdfs/server/datanode/checker/AsyncChecker.java ---
    @@ -0,0 +1,62 @@
    +/**
    + * 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
    + * <p>
    + * http://www.apache.org/licenses/LICENSE-2.0
    + * <p>
    + * 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.hadoop.hdfs.server.datanode.checker;
    +
    +import com.google.common.util.concurrent.ListenableFuture;
    +import org.apache.hadoop.classification.InterfaceAudience;
    +import org.apache.hadoop.classification.InterfaceStability;
    +
    +import java.util.concurrent.ExecutorService;
    +import java.util.concurrent.TimeUnit;
    +
    +/**
    + * A class that can be used to schedule an asynchronous check on a given
    + * {@link Checkable}. If the check is successfully scheduled then a
    + * {@link ListenableFuture} is returned.
    + *
    + */
    +@InterfaceAudience.Private
    +@InterfaceStability.Unstable
    +public interface AsyncChecker<K, V> {
    +
    +  /**
    +   * Schedule an asynchronous check for the given object.
    +   *
    +   * @param target object to be checked.
    +   *
    +   * @param context the interpretation of the context depends on the
    +   *                target.
    +   *
    +   * @return returns a {@link ListenableFuture} that can be used to
    +   *         retrieve the result of the asynchronous check.
    +   */
    +  ListenableFuture<V> schedule(Checkable<K, V> target, K context);
    +
    +  /**
    +   * Cancel all executing checks and wait for them to complete.
    +   * First attempts a graceful cancellation, then cancels forcefully.
    +   * Waits for the supplied timeout after both attempts.
    +   *
    +   * See {@link ExecutorService#awaitTermination} for a description of
    +   * the parameters.
    +   *
    +   * @throws InterruptedException
    +   */
    +  void join(long timeout, TimeUnit timeUnit) throws InterruptedException;
    --- End diff --
    
    Just trying to understand this a little better, From the signature and implementation this function looks more a awaitTermination in executorService. That is this function will wait for a while and cancel and task if the timeout occurs, in that case would you consider calling this await or awaitTermination. Java "join" seems to imply a wait without timeouts. Just making sure that the intended was indeed a shutdown/await pattern.


> Support for running async disk checks in DataNode
> -------------------------------------------------
>
>                 Key: HDFS-11114
>                 URL: https://issues.apache.org/jira/browse/HDFS-11114
>             Project: Hadoop HDFS
>          Issue Type: Sub-task
>          Components: datanode
>            Reporter: Arpit Agarwal
>            Assignee: Arpit Agarwal
>         Attachments: HDFS-11114.01.patch, HDFS-11114.02.patch
>
>
> Introduce support for running async checks.


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