HADOOP-16858. S3Guard fsck: Add option to remove orphaned entries (#1851). Contributed by Gabor Bota.

Adding a new feature to S3GuardTool's fsck: -fix. 

Change-Id: I2cdb6601fea1d859b54370046b827ef06eb1107d

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/s3guard/S3GuardFsck.java

@@ -159,7 +159,9 @@ public class S3GuardFsck {
     // Create a handler and handle each violated pairs
     S3GuardFsckViolationHandler handler =
         new S3GuardFsckViolationHandler(rawFS, metadataStore);
-    comparePairs.forEach(handler::handle);
+    for (ComparePair comparePair : comparePairs) {
+      handler.logError(comparePair);
+    }
 
     LOG.info("Total scan time: {}s", stopwatch.now(TimeUnit.SECONDS));
     LOG.info("Scanned entries: {}", scannedItems);
@@ -344,6 +346,31 @@ public class S3GuardFsck {
     return rawFS.makeQualified(new Path(s));
   }
 
+  /**
+   * Fix violations found during check.
+   *
+   * Currently only supports handling the following violation:
+   * - Violation.ORPHAN_DDB_ENTRY
+   *
+   * @param violations to be handled
+   * @throws IOException throws the error if there's any during handling
+   */
+  public void fixViolations(List<ComparePair> violations) throws IOException {
+    S3GuardFsckViolationHandler handler =
+        new S3GuardFsckViolationHandler(rawFS, metadataStore);
+
+    for (ComparePair v : violations) {
+      if (v.getViolations().contains(Violation.ORPHAN_DDB_ENTRY)) {
+        try {
+          handler.doFix(v);
+        } catch (IOException e) {
+          LOG.error("Error during handling the violation: ", e);
+          throw e;
+        }
+      }
+    }
+  }
+
   /**
    * A compare pair with the pair of metadata and the list of violations.
    */
@@ -542,7 +569,9 @@ public class S3GuardFsck {
     // Create a handler and handle each violated pairs
     S3GuardFsckViolationHandler handler =
         new S3GuardFsckViolationHandler(rawFS, metadataStore);
-    comparePairs.forEach(handler::handle);
+    for (ComparePair comparePair : comparePairs) {
+      handler.logError(comparePair);
+    }
 
     stopwatch.stop();
     LOG.info("Total scan time: {}s", stopwatch.now(TimeUnit.SECONDS));

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/s3guard/S3GuardFsckViolationHandler.java

@@ -18,6 +18,7 @@
 
 package org.apache.hadoop.fs.s3a.s3guard;
 
+import java.io.IOException;
 import java.lang.reflect.InvocationTargetException;
 import java.util.Arrays;
 import java.util.List;
@@ -26,6 +27,7 @@ import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import org.apache.hadoop.fs.FileStatus;
+import org.apache.hadoop.fs.Path;
 import org.apache.hadoop.fs.s3a.S3AFileStatus;
 import org.apache.hadoop.fs.s3a.S3AFileSystem;
 
@@ -43,6 +45,10 @@ public class S3GuardFsckViolationHandler {
 
   private static String newLine = System.getProperty("line.separator");
 
+  public enum HandleMode {
+    FIX, LOG
+  }
+
   public S3GuardFsckViolationHandler(S3AFileSystem fs,
       DynamoDBMetadataStore ddbms) {
 
@@ -50,7 +56,7 @@ public class S3GuardFsckViolationHandler {
     this.rawFs = fs;
   }
 
-  public void handle(S3GuardFsck.ComparePair comparePair) {
+  public void logError(S3GuardFsck.ComparePair comparePair) throws IOException {
     if (!comparePair.containsViolation()) {
       LOG.debug("There is no violation in the compare pair: {}", comparePair);
       return;
@@ -60,11 +66,26 @@ public class S3GuardFsckViolationHandler {
     sB.append(newLine)
         .append("On path: ").append(comparePair.getPath()).append(newLine);
 
-    handleComparePair(comparePair, sB);
+    handleComparePair(comparePair, sB, HandleMode.LOG);
 
     LOG.error(sB.toString());
   }
 
+  public void doFix(S3GuardFsck.ComparePair comparePair) throws IOException {
+    if (!comparePair.containsViolation()) {
+      LOG.debug("There is no violation in the compare pair: {}", comparePair);
+      return;
+    }
+
+    StringBuilder sB = new StringBuilder();
+    sB.append(newLine)
+        .append("On path: ").append(comparePair.getPath()).append(newLine);
+
+    handleComparePair(comparePair, sB, HandleMode.FIX);
+
+    LOG.info(sB.toString());
+  }
+
   /**
    * Create a new instance of the violation handler for all the violations
    * found in the compare pair and use it.
@@ -72,16 +93,28 @@ public class S3GuardFsckViolationHandler {
    * @param comparePair the compare pair with violations
    * @param sB StringBuilder to append error strings from violations.
    */
-  protected static void handleComparePair(S3GuardFsck.ComparePair comparePair,
-      StringBuilder sB) {
+  protected void handleComparePair(S3GuardFsck.ComparePair comparePair,
+      StringBuilder sB, HandleMode handleMode) throws IOException {
 
     for (S3GuardFsck.Violation violation : comparePair.getViolations()) {
       try {
         ViolationHandler handler = violation.getHandler()
             .getDeclaredConstructor(S3GuardFsck.ComparePair.class)
             .newInstance(comparePair);
+
+        switch (handleMode) {
+          case FIX:
             final String errorStr = handler.getError();
             sB.append(errorStr);
+            break;
+          case LOG:
+            final String fixStr = handler.fixViolation(rawFs, metadataStore);
+            sB.append(fixStr);
+            break;
+          default:
+            throw new UnsupportedOperationException("Unknown handleMode: " + handleMode);
+        }
+
       } catch (NoSuchMethodException e) {
         LOG.error("Can not find declared constructor for handler: {}",
             violation.getHandler());
@@ -137,6 +170,12 @@ public class S3GuardFsckViolationHandler {
     public DirListingMetadata getMsDirListing() {
       return msDirListing;
     }
+
+    public String fixViolation(S3AFileSystem fs,
+        DynamoDBMetadataStore ddbms) throws IOException {
+      return String.format("Fixing of violation: %s is not supported yet.",
+          this.getClass().getSimpleName());
+    }
   }
 
   /**
@@ -357,6 +396,16 @@ public class S3GuardFsckViolationHandler {
     public String getError() {
       return "The DDB entry is orphan - there is no parent in the MS.";
     }
+
+    @Override
+    public String fixViolation(S3AFileSystem fs, DynamoDBMetadataStore ddbms)
+        throws IOException {
+      final Path path = getPathMetadata().getFileStatus().getPath();
+      ddbms.forgetMetadata(path);
+      return String.format(
+          "Fixing violation by removing metadata entry from the " +
+              "MS on path: %s", path);
+    }
   }
 
   /**

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/s3guard/S3GuardTool.java

@@ -25,6 +25,7 @@ import java.io.PrintStream;
 import java.net.URI;
 import java.net.URISyntaxException;
 import java.nio.file.AccessDeniedException;
+import java.util.Arrays;
 import java.util.Collection;
 import java.util.Date;
 import java.util.HashMap;
@@ -1609,6 +1610,7 @@ public abstract class S3GuardTool extends Configured implements Tool,
   static class Fsck extends S3GuardTool {
     public static final String CHECK_FLAG = "check";
     public static final String DDB_MS_CONSISTENCY_FLAG = "internal";
+    public static final String FIX_FLAG = "fix";
 
     public static final String NAME = "fsck";
     public static final String PURPOSE = "Compares S3 with MetadataStore, and "
@@ -1618,12 +1620,17 @@ public abstract class S3GuardTool extends Configured implements Tool,
         "\t" + PURPOSE + "\n\n" +
         "Common options:\n" +
         "  -" + CHECK_FLAG + " Check the metadata store for errors, but do "
-        + "not fix any issues.\n"+
+        + "not fix any issues.\n" +
         "  -" + DDB_MS_CONSISTENCY_FLAG + " Check the dynamodb metadata store "
-        + "for internal consistency.\n";
+        + "for internal consistency.\n" +
+        "  -" + FIX_FLAG + " Fix the errors found in the metadata store. Can " +
+        "be used with " + CHECK_FLAG + " or " + DDB_MS_CONSISTENCY_FLAG + " flags. "
+        + "\n\t\tFixes: \n" +
+        "\t\t\t- Remove orphan entries from DDB." +
+        "\n";
 
     Fsck(Configuration conf) {
-      super(conf, CHECK_FLAG, DDB_MS_CONSISTENCY_FLAG);
+      super(conf, CHECK_FLAG, DDB_MS_CONSISTENCY_FLAG, FIX_FLAG);
     }
 
     @Override
@@ -1648,17 +1655,19 @@ public abstract class S3GuardTool extends Configured implements Tool,
       final CommandFormat commandFormat = getCommandFormat();
 
       // check if there's more than one arguments
-      int flags = 0;
-      if (commandFormat.getOpt(CHECK_FLAG)) {
-        flags++;
-      }
-      if (commandFormat.getOpt(DDB_MS_CONSISTENCY_FLAG)) {
-        flags++;
-      }
+      // from CHECK and INTERNAL CONSISTENCY
+      int flags = countTrue(commandFormat.getOpt(CHECK_FLAG),
+          commandFormat.getOpt(DDB_MS_CONSISTENCY_FLAG));
       if (flags > 1) {
         out.println(USAGE);
         throw invalidArgs("There should be only one parameter used for checking.");
       }
+      if (flags == 0 && commandFormat.getOpt(FIX_FLAG)) {
+        errorln(FIX_FLAG + " flag can be used with either " + CHECK_FLAG + " or " +
+            DDB_MS_CONSISTENCY_FLAG + " flag, but not alone.");
+        errorln(USAGE);
+        return ERROR;
+      }
 
       String s3Path = paths.get(0);
       try {
@@ -1707,6 +1716,11 @@ public abstract class S3GuardTool extends Configured implements Tool,
         return ERROR;
       }
 
+      if (commandFormat.getOpt(FIX_FLAG)) {
+        S3GuardFsck s3GuardFsck = new S3GuardFsck(fs, ms);
+        s3GuardFsck.fixViolations(violations);
+      }
+
       out.flush();
 
       // We fail if there were compare pairs, as the returned compare pairs
@@ -1716,6 +1730,10 @@ public abstract class S3GuardTool extends Configured implements Tool,
       }
       return exitValue;
     }
+
+    int countTrue(Boolean... bools) {
+      return (int) Arrays.stream(bools).filter(p -> p).count();
+    }
   }
   /**
    * Audits a DynamoDB S3Guard repository for all the entries being

hadoop-tools/hadoop-aws/src/site/markdown/tools/hadoop-aws/s3guard.md

@@ -1165,7 +1165,7 @@ Compares S3 with MetadataStore, and returns a failure status if any
 rules or invariants are violated. Only works with DynamoDB metadata stores.
 
 ```bash
-hadoop s3guard fsck [-check | -internal] (s3a://BUCKET | s3a://PATH_PREFIX)
+hadoop s3guard fsck [-check | -internal] [-fix] (s3a://BUCKET | s3a://PATH_PREFIX)
 ```
 
 `-check` operation checks the metadata store from the S3 perspective, but
@@ -1175,6 +1175,12 @@ The consistency issues will be logged in ERROR loglevel.
 `-internal` operation checks the internal consistency of the metadata store,
 but does not fix any issues.
 
+`-fix` operation fixes consistency issues between the metadatastore and the S3
+bucket. This parameter is optional, and can be used together with check or
+internal parameters, but not alone.
+The following fix is implemented:
+- Remove orphan entries from DDB
+
 The errors found will be logged at the ERROR log level.
 
 *Note*: `-check` and `-internal` operations can be used only as separate

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/ITestS3GuardFsck.java

@@ -24,6 +24,7 @@ import java.net.URI;
 import java.util.Collections;
 import java.util.List;
 import java.util.UUID;
+import java.util.stream.Collectors;
 
 import org.assertj.core.api.Assertions;
 import org.junit.Before;
@@ -499,6 +500,19 @@ public class ITestS3GuardFsck extends AbstractS3ATestBase {
       assertComparePairsSize(comparePairs, 1);
       checkForViolationInPairs(file, comparePairs,
           S3GuardFsck.Violation.ORPHAN_DDB_ENTRY);
+
+      // fix the violation
+      s3GuardFsck.fixViolations(
+          comparePairs.stream().filter(cP -> cP.getViolations()
+              .contains(S3GuardFsck.Violation.ORPHAN_DDB_ENTRY))
+              .collect(Collectors.toList())
+      );
+
+      // assert that the violation is fixed
+      final List<S3GuardFsck.ComparePair> fixedComparePairs =
+          s3GuardFsck.checkDdbInternalConsistency(cwd);
+      checkNoViolationInPairs(file, fixedComparePairs,
+          S3GuardFsck.Violation.ORPHAN_DDB_ENTRY);
     } finally {
       cleanup(file, cwd);
     }
@@ -596,14 +610,27 @@ public class ITestS3GuardFsck extends AbstractS3ATestBase {
         .contains(violation);
   }
 
-  private void checkNoViolationInPairs(Path file2,
+  /**
+   * Check that there is no violation in the pair provided.
+   *
+   * @param file the path to filter to in the comparePairs list.
+   * @param comparePairs the list to validate.
+   * @param violation the violation that should not be in the list.
+   */
+  private void checkNoViolationInPairs(Path file,
       List<S3GuardFsck.ComparePair> comparePairs,
       S3GuardFsck.Violation violation) {
-    final S3GuardFsck.ComparePair file2Pair = comparePairs.stream()
-        .filter(p -> p.getPath().equals(file2))
+
+    if (comparePairs.size() == 0) {
+      LOG.info("Compare pairs is empty, so there's no violation. (As expected.)");
+      return;
+    }
+
+    final S3GuardFsck.ComparePair comparePair = comparePairs.stream()
+        .filter(p -> p.getPath().equals(file))
         .findFirst().get();
-    assertNotNull("The pair should not be null.", file2Pair);
-    Assertions.assertThat(file2Pair.getViolations())
+    assertNotNull("The pair should not be null.", comparePair);
+    Assertions.assertThat(comparePair.getViolations())
         .describedAs("Violations in the pair")
         .doesNotContain(violation);
   }

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/ITestS3GuardToolDynamoDB.java

@@ -354,6 +354,40 @@ public class ITestS3GuardToolDynamoDB extends AbstractS3GuardToolTestBase {
         "s3a://" + getFileSystem().getBucket()));
   }
 
+  @Test
+  public void testCLIFsckDDbFixOnlyFails() throws Exception {
+    describe("This test serves the purpose to run fsck with the correct " +
+        "parameters, so there will be no exception thrown.");
+    final int result = run(S3GuardTool.Fsck.NAME,
+        "-" + Fsck.FIX_FLAG,
+        "s3a://" + getFileSystem().getBucket());
+    LOG.info("The return value of the run: {}", result);
+    assertEquals(ERROR, result);
+  }
+
+  /**
+   * Test that the fix flag is accepted by the fsck.
+   *
+   * Note that we don't have an assert at the end of this test because
+   * there maybe some errors found during the check and the returned value
+   * will be ERROR and not SUCCESS. So if we assert on SUCCESS, then the test
+   * could (likely) to be flaky.
+   * If the FIX_FLAG parameter is not accepted here an exception will be thrown
+   * so the test will break.
+   *
+   * @throws Exception
+   */
+  @Test
+  public void testCLIFsckDDbFixAndInternalSucceed() throws Exception {
+    describe("This test serves the purpose to run fsck with the correct " +
+        "parameters, so there will be no exception thrown.");
+    final int result = run(S3GuardTool.Fsck.NAME,
+        "-" + Fsck.FIX_FLAG,
+        "-" + Fsck.DDB_MS_CONSISTENCY_FLAG,
+        "s3a://" + getFileSystem().getBucket());
+    LOG.info("The return value of the run: {}", result);
+  }
+
   /**
    * Test that when init, the CMK option can not live without SSE enabled.
    */