[GitHub] [crunch] noslowerdna commented on a change in pull request #20: CRUNCH-679: Improvements for usage of DistCp

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noslowerdna commented on a change in pull request #20: CRUNCH-679: Improvements for usage of DistCp
URL: https://github.com/apache/crunch/pull/20#discussion_r262615465
 
 

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 File path: crunch-core/src/main/java/org/apache/crunch/util/CrunchRenameCopyListing.java
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+/**
+ * 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.crunch.util;
+
+import org.apache.hadoop.conf.Configuration;
+import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.FileSystem;
+import org.apache.hadoop.fs.Path;
+import org.apache.hadoop.io.SequenceFile;
+import org.apache.hadoop.io.Text;
+import org.apache.hadoop.security.Credentials;
+import org.apache.hadoop.tools.CopyListing;
+import org.apache.hadoop.tools.CopyListingFileStatus;
+import org.apache.hadoop.tools.DistCpOptions;
+import org.apache.hadoop.tools.DistCpOptions.FileAttribute;
+import org.apache.hadoop.tools.SimpleCopyListing;
+import org.apache.hadoop.tools.util.DistCpUtils;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.Stack;
+
+/**
+ * A custom {@link CopyListing} implementation capable of dynamically renaming
+ * the target paths according to a configured set of values.
+ * <p>
+ * Once https://issues.apache.org/jira/browse/HADOOP-16147 is available, this
+ * class can be significantly simplified.
+ * </p>
+ */
+public class CrunchRenameCopyListing extends SimpleCopyListing {
+  /**
+   * Comma-separated list of original-file:renamed-file path rename pairs.
+   */
+  public static final String DISTCP_PATH_RENAMES = "crunch.distcp.path.renames";
+
+  private static final Logger LOG = LoggerFactory.getLogger(CrunchRenameCopyListing.class);
+  private final Map<String, String> pathRenames;
+
+  private long totalPaths = 0;
+  private long totalBytesToCopy = 0;
+
+  /**
+   * Protected constructor, to initialize configuration.
+   *
+   * @param configuration The input configuration, with which the source/target FileSystems may be accessed.
+   * @param credentials - Credentials object on which the FS delegation tokens are cached. If null
+   * delegation token caching is skipped
+   */
+  protected CrunchRenameCopyListing(Configuration configuration, Credentials credentials) {
+    super(configuration, credentials);
+
+    pathRenames = new HashMap<>();
+
+    String[] pathRenameConf = configuration.getStrings(DISTCP_PATH_RENAMES);
 
 Review comment:
   I ran some tests and did not encounter any problems I would consider showstopping. My largest concern is it appeared that the DistCp job completion time was delayed roughly proportionally to the size of the configuration, with a delay of nearly two minutes observed in the worst case test - I think probably due to persisting the configuration into job history. 
   
   ```
   19/03/05 11:04:53 INFO mapreduce.Job:  map 100% reduce 0%
   19/03/05 11:06:48 INFO mapreduce.Job: Job job_1538164922410_717171 completed successfully
   ```
   
   Otherwise everything looked good, and viewing the job configuration through the web UI worked fine although slow when the size was in multiple MBs.
   
   The configuration property value size was retrieved by,
   ```
   conf.get(CrunchRenameCopyListing.DISTCP_PATH_RENAMES).length()
   ```
   
   Number of part files | Configuration size | Completion delay
   -- | -- | --
   10k | 260kb | 0:05
   50k | 1.3mb | 0:29
   250k | 6.8mb | 0:54
   500k | 13.8mb | 1:55

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