[GitHub] [hadoop] kai33 commented on a change in pull request #919: HADOOP-16158. DistCp to support checksum validation when copy blocks in parallel

[GitBox <gi...@apache.org>]

kai33 commented on a change in pull request #919: HADOOP-16158. DistCp to support checksum validation when copy blocks in parallel
URL: https://github.com/apache/hadoop/pull/919#discussion_r313064959
 
 

 ##########
 File path: hadoop-tools/hadoop-distcp/src/main/java/org/apache/hadoop/tools/util/DistCpUtils.java
 ##########
 @@ -583,6 +583,63 @@ public static boolean checksumsAreEqual(FileSystem sourceFS, Path source,
             sourceChecksum.equals(targetChecksum));
   }
 
+  /**
+   * Utility to compare file lengths and checksums for source and target.
+   *
+   * @param sourceFS FileSystem for the source path.
+   * @param source The source path.
+   * @param sourceChecksum The checksum of the source file. If it is null we
+   * still need to retrieve it through sourceFS.
+   * @param targetFS FileSystem for the target path.
+   * @param target The target path.
+   * @param skipCrc The flag to indicate whether to skip checksums.
+   * @throws IOException if there's a mismatch in file lengths or checksums.
+   */
+  public static void compareFileLengthsAndChecksums(
+      FileSystem sourceFS, Path source, FileChecksum sourceChecksum,
+      FileSystem targetFS, Path target, boolean skipCrc) throws IOException {
+    long srcLen = sourceFS.getFileStatus(source).getLen();
+    long tgtLen = targetFS.getFileStatus(target).getLen();
+    if (srcLen != tgtLen) {
+      throw new IOException(
+          "Mismatch in length of source:" + source + " (" + srcLen
+              + ") and target:" + target + " (" + tgtLen + ")");
+    }
+
+    //At this point, src & dest lengths are same. if length==0, we skip checksum
+    if ((srcLen != 0) && (!skipCrc)) {
+      if (!checksumsAreEqual(sourceFS, source, sourceChecksum,
+          targetFS, target)) {
+        StringBuilder errorMessage =
+            new StringBuilder("Checksum mismatch between ")
+                .append(source).append(" and ").append(target).append(".");
+        boolean addSkipHint = false;
+        String srcScheme = sourceFS.getScheme();
+        String targetScheme = targetFS.getScheme();
+        if (!srcScheme.equals(targetScheme)
+            && !(srcScheme.contains("hdfs") && targetScheme.contains("hdfs"))) {
 
 Review comment:
   removed in the latest commit

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