YARN-5277. When localizers fail due to resource timestamps being out, provide more diagnostics. Contributed by Siddharth Ahuja

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/main/java/org/apache/hadoop/yarn/util/FSDownload.java

@@ -32,6 +32,7 @@ import java.util.regex.Pattern;
 
 import org.apache.commons.io.FileUtils;
 import org.apache.commons.io.IOUtils;
+import org.apache.hadoop.util.Time;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 import org.apache.hadoop.classification.InterfaceAudience.LimitedPrivate;
@@ -269,9 +270,12 @@ public class FSDownload implements Callable<Path> {
     FileSystem sourceFs = sCopy.getFileSystem(conf);
     FileStatus sStat = sourceFs.getFileStatus(sCopy);
     if (sStat.getModificationTime() != resource.getTimestamp()) {
-      throw new IOException("Resource " + sCopy +
-          " changed on src filesystem (expected " + resource.getTimestamp() +
-          ", was " + sStat.getModificationTime());
+      throw new IOException("Resource " + sCopy + " changed on src filesystem" +
+          " - expected: " +
+          "\"" + Times.formatISO8601(resource.getTimestamp()) + "\"" +
+          ", was: " +
+          "\"" + Times.formatISO8601(sStat.getModificationTime()) + "\"" +
+          ", current time: " + "\"" + Times.formatISO8601(Time.now()) + "\"");
     }
     if (resource.getVisibility() == LocalResourceVisibility.PUBLIC) {
       if (!isPublic(sourceFs, sCopy, sStat, statCache)) {

hadoop-yarn-project/hadoop-yarn/hadoop-yarn-common/src/test/java/org/apache/hadoop/yarn/util/TestFSDownload.java

@@ -711,4 +711,78 @@ public class TestFSDownload {
     // destination directory (passed as an argument) + file name.
     Assert.assertEquals(destPath, rPath.get().getParent());
   }
+
+  /**
+   * This test method is responsible for creating an IOException resulting
+   * from modification to the local resource's timestamp on the source FS just
+   * before the download of this local resource has started.
+   */
+  @Test(timeout=10000)
+  public void testResourceTimestampChangeDuringDownload()
+      throws IOException, InterruptedException {
+    conf = new Configuration();
+    FileContext files = FileContext.getLocalFSFileContext(conf);
+    final Path basedir = files.makeQualified(
+        new Path("target", TestFSDownload.class.getSimpleName()));
+    files.mkdir(basedir, null, true);
+    conf.setStrings(TestFSDownload.class.getName(), basedir.toString());
+
+    LocalDirAllocator dirs =
+        new LocalDirAllocator(TestFSDownload.class.getName());
+
+    Path path = new Path(basedir, "test-file");
+    Random rand = new Random();
+    long sharedSeed = rand.nextLong();
+    rand.setSeed(sharedSeed);
+    int size = 512;
+    LocalResourceVisibility vis = LocalResourceVisibility.PUBLIC;
+    LocalResource localResource = createFile(files, path, size, rand, vis);
+
+    Path destPath = dirs.getLocalPathForWrite(basedir.toString(), size, conf);
+    destPath = new Path(destPath,
+        Long.toString(uniqueNumberGenerator.incrementAndGet()));
+
+    FSDownload fsDownload = new FSDownload(files,
+        UserGroupInformation.getCurrentUser(), conf, destPath, localResource);
+
+    // Store the original local resource timestamp used to set up the
+    // FSDownload object just before (but before the download starts)
+    // for comparison purposes later on.
+    long origLRTimestamp = localResource.getTimestamp();
+
+    // Modify the local resource's timestamp to yesterday on the Filesystem
+    // just before FSDownload starts.
+    final long msInADay = 86400 * 1000;
+    long modifiedFSTimestamp = origLRTimestamp - msInADay;
+    try {
+      Path sourceFsPath = localResource.getResource().toPath();
+      FileSystem sourceFs = sourceFsPath.getFileSystem(conf);
+      sourceFs.setTimes(sourceFsPath, modifiedFSTimestamp, modifiedFSTimestamp);
+    } catch (URISyntaxException use) {
+      Assert.fail("No exception expected.");
+    }
+
+    // Execute the FSDownload operation.
+    Map<LocalResource, Future<Path>> pending = new HashMap<>();
+    ExecutorService exec = HadoopExecutors.newSingleThreadExecutor();
+    pending.put(localResource, exec.submit(fsDownload));
+
+    exec.shutdown();
+
+    exec.awaitTermination(1000, TimeUnit.MILLISECONDS);
+    Assert.assertTrue(pending.get(localResource).isDone());
+
+    try {
+      for (Map.Entry<LocalResource, Future<Path>> p : pending.entrySet()) {
+        p.getValue().get();
+      }
+      Assert.fail("Exception expected from timestamp update during download");
+    } catch (ExecutionException ee) {
+      Assert.assertTrue(ee.getCause() instanceof IOException);
+      Assert.assertTrue("Exception contains original timestamp",
+          ee.getMessage().contains(Times.formatISO8601(origLRTimestamp)));
+      Assert.assertTrue("Exception contains modified timestamp",
+          ee.getMessage().contains(Times.formatISO8601(modifiedFSTimestamp)));
+    }
+  }
 }