[jira] [Commented] (TWILL-158) Provides an implementation of Location and LocationFactory using FileContext instead of FileSystem

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/TWILL-158?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15081865#comment-15081865 ] 

ASF GitHub Bot commented on TWILL-158:
--------------------------------------

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

    https://github.com/apache/incubator-twill/pull/73#discussion_r48784930
  
    --- Diff: twill-yarn/src/main/java/org/apache/twill/filesystem/FileContextLocationFactory.java ---
    @@ -0,0 +1,119 @@
    +/*
    + * 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.twill.filesystem;
    +
    +import com.google.common.base.Preconditions;
    +import com.google.common.base.Throwables;
    +import org.apache.hadoop.conf.Configuration;
    +import org.apache.hadoop.fs.FileContext;
    +import org.apache.hadoop.fs.Path;
    +import org.apache.hadoop.fs.UnsupportedFileSystemException;
    +
    +import java.net.URI;
    +import java.util.Objects;
    +
    +/**
    + * A {@link LocationFactory} implementation that uses {@link FileContext} to create {@link Location}.
    + */
    +public class FileContextLocationFactory implements LocationFactory {
    +
    +  private final Configuration configuration;
    +  private final FileContext fc;
    +  private final Path pathBase;
    +
    +  /**
    +   * Same as {@link #FileContextLocationFactory(Configuration, String) FileContextLocationFactory(configuration, "/")}.
    +   */
    +  public FileContextLocationFactory(Configuration configuration) {
    +    this(configuration, "/");
    +  }
    +
    +  /**
    +   * Creates a new instance.
    +   *
    +   * @param configuration the hadoop configuration
    +   * @param pathBase base path for all non-absolute location created through this {@link LocationFactory}.
    +   */
    +  public FileContextLocationFactory(Configuration configuration, String pathBase) {
    +    this.configuration = configuration;
    +    this.fc = createFileContext(configuration);
    +    this.pathBase = new Path(pathBase.startsWith("/") ? pathBase : "/" + pathBase);
    +  }
    +
    +  @Override
    +  public Location create(String path) {
    +    if (path.startsWith("/")) {
    +      path = path.substring(1);
    +    }
    +    Path locationPath;
    +    if (path.isEmpty()) {
    +      locationPath = pathBase;
    +    } else {
    +      locationPath = new Path(path);
    +    }
    +    locationPath = locationPath.makeQualified(fc.getDefaultFileSystem().getUri(), pathBase);
    +    return new FileContextLocation(this, fc, locationPath);
    +  }
    +
    +  @Override
    +  public Location create(URI uri) {
    +    URI contextURI = fc.getWorkingDirectory().toUri();
    +    if (Objects.equals(contextURI.getScheme(), uri.getScheme())
    +      && Objects.equals(contextURI.getAuthority(), uri.getAuthority())) {
    +      // A full URI
    +      return new FileContextLocation(this, fc, new Path(uri));
    +    }
    +
    +    if (uri.isAbsolute()) {
    --- End diff --
    
    It will be good to have a comment on what a full URI and an absolute URI mean.


> Provides an implementation of Location and LocationFactory using FileContext instead of FileSystem
> --------------------------------------------------------------------------------------------------
>
>                 Key: TWILL-158
>                 URL: https://issues.apache.org/jira/browse/TWILL-158
>             Project: Apache Twill
>          Issue Type: New Feature
>            Reporter: Terence Yim
>            Assignee: Terence Yim
>             Fix For: 0.7.0-incubating
>
>
> FileContext is more intended for application developer. It provides better support for the rename operation, while the current FileSystem one uses a hacky way to implement rename().



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