HADOOP-14759 S3GuardTool prune to prune specific bucket entries. Contributed by Gabor Bota.

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

@@ -812,23 +812,33 @@ public class DynamoDBMetadataStore implements MetadataStore {
   }
 
   @Retries.OnceRaw
-  private ItemCollection<ScanOutcome> expiredFiles(long modTime) {
-    String filterExpression = "mod_time < :mod_time";
+  private ItemCollection<ScanOutcome> expiredFiles(long modTime,
+      String keyPrefix) {
+    String filterExpression =
+        "mod_time < :mod_time and begins_with(parent, :parent)";
     String projectionExpression = "parent,child";
-    ValueMap map = new ValueMap().withLong(":mod_time", modTime);
+    ValueMap map = new ValueMap()
+        .withLong(":mod_time", modTime)
+        .withString(":parent", keyPrefix);
     return table.scan(filterExpression, projectionExpression, null, map);
   }
 
   @Override
   @Retries.OnceRaw("once(batchWrite)")
   public void prune(long modTime) throws IOException {
+    prune(modTime, "/");
+  }
+
+  @Override
+  @Retries.OnceRaw("once(batchWrite)")
+  public void prune(long modTime, String keyPrefix) throws IOException {
     int itemCount = 0;
     try {
       Collection<Path> deletionBatch =
           new ArrayList<>(S3GUARD_DDB_BATCH_WRITE_REQUEST_LIMIT);
       int delay = conf.getInt(S3GUARD_DDB_BACKGROUND_SLEEP_MSEC_KEY,
           S3GUARD_DDB_BACKGROUND_SLEEP_MSEC_DEFAULT);
-      for (Item item : expiredFiles(modTime)) {
+      for (Item item : expiredFiles(modTime, keyPrefix)) {
         PathMetadata md = PathMetadataDynamoDBTranslation
             .itemToPathMetadata(item, username);
         Path path = md.getFileStatus().getPath();

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

@@ -303,12 +303,18 @@ public class LocalMetadataStore implements MetadataStore {
   }
 
   @Override
-  public synchronized void prune(long modTime) throws IOException {
+  public void prune(long modTime) throws IOException{
+    prune(modTime, "");
+  }
+
+  @Override
+  public synchronized void prune(long modTime, String keyPrefix)
+      throws IOException {
     Iterator<Map.Entry<Path, PathMetadata>> files =
         fileHash.entrySet().iterator();
     while (files.hasNext()) {
       Map.Entry<Path, PathMetadata> entry = files.next();
-      if (expired(entry.getValue().getFileStatus(), modTime)) {
+      if (expired(entry.getValue().getFileStatus(), modTime, keyPrefix)) {
         files.remove();
       }
     }
@@ -323,7 +329,7 @@ public class LocalMetadataStore implements MetadataStore {
 
       for (PathMetadata child : oldChildren) {
         FileStatus status = child.getFileStatus();
-        if (!expired(status, modTime)) {
+        if (!expired(status, modTime, keyPrefix)) {
           newChildren.add(child);
         }
       }
@@ -339,10 +345,11 @@ public class LocalMetadataStore implements MetadataStore {
     }
   }
 
-  private boolean expired(FileStatus status, long expiry) {
+  private boolean expired(FileStatus status, long expiry, String keyPrefix) {
     // Note: S3 doesn't track modification time on directories, so for
     // consistency with the DynamoDB implementation we ignore that here
-    return status.getModificationTime() < expiry && !status.isDirectory();
+    return status.getModificationTime() < expiry && !status.isDirectory()
+      && status.getPath().toString().startsWith(keyPrefix);
   }
 
   @VisibleForTesting

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

@@ -223,6 +223,18 @@ public interface MetadataStore extends Closeable {
    */
   void prune(long modTime) throws IOException, UnsupportedOperationException;
 
+  /**
+   * Same as {@link MetadataStore#prune(long)}, but with an additional
+   * keyPrefix parameter to filter the pruned keys with a prefix.
+   *
+   * @param modTime Oldest modification time to allow
+   * @param keyPrefix The prefix for the keys that should be removed
+   * @throws IOException if there is an error
+   * @throws UnsupportedOperationException if not implemented
+   */
+  void prune(long modTime, String keyPrefix)
+      throws IOException, UnsupportedOperationException;
+
   /**
    * Get any diagnostics information from a store, as a list of (key, value)
    * tuples for display. Arbitrary values; no guarantee of stability.

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

@@ -99,6 +99,10 @@ public class NullMetadataStore implements MetadataStore {
   public void prune(long modTime) {
   }
 
+  @Override
+  public void prune(long modTime, String keyPrefix) {
+  }
+
   @Override
   public String toString() {
     return "NullMetadataStore";

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

@@ -966,8 +966,16 @@ public abstract class S3GuardTool extends Configured implements Tool {
       long now = System.currentTimeMillis();
       long divide = now - delta;
 
+      // remove the protocol from path string to get keyPrefix
+      // by default the keyPrefix is "/" - unless the s3 URL is provided
+      String keyPrefix = "/";
+      if(paths.size() > 0) {
+        Path path = new Path(paths.get(0));
+        keyPrefix = PathMetadataDynamoDBTranslation.pathToParentKey(path);
+      }
+
       try {
-        getStore().prune(divide);
+        getStore().prune(divide, keyPrefix);
       } catch (UnsupportedOperationException e){
         errorln("Prune operation not supported in metadata store.");
       }

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

@@ -592,8 +592,8 @@ A time value of hours, minutes and/or seconds must be supplied.
 1. This does not delete the entries in the bucket itself.
 1. The modification time is effectively the creation time of the objects
 in the S3 Bucket.
-1. Even when an S3A URI is supplied, all entries in the table older than
-a specific age are deleted — even those from other buckets.
+1. If an S3A URI is supplied, only the entries in the table specified by the
+URI and older than a specific age are deleted.
 
 Example
 
@@ -604,6 +604,13 @@ hadoop s3guard prune -days 7 s3a://ireland-1
 Deletes all entries in the S3Guard table for files older than seven days from
 the table associated with `s3a://ireland-1`.
 
+```bash
+hadoop s3guard prune -days 7 s3a://ireland-1/path_prefix/
+```
+
+Deletes all entries in the S3Guard table for files older than seven days from
+the table associated with `s3a://ireland-1` and with the prefix "path_prefix"
+
 ```bash
 hadoop s3guard prune -hours 1 -minutes 30 -meta dynamodb://ireland-team -region eu-west-1
 ```

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/s3a/s3guard/AbstractS3GuardToolTestBase.java

@@ -181,22 +181,26 @@ public abstract class AbstractS3GuardToolTestBase extends AbstractS3ATestBase {
     }
   }
 
-  private void testPruneCommand(Configuration cmdConf, String...args)
-      throws Exception {
-    Path parent = path("prune-cli");
+  private void testPruneCommand(Configuration cmdConf, Path parent,
+      String...args) throws Exception {
+    Path keepParent = path("prune-cli-keep");
     try {
       getFileSystem().mkdirs(parent);
+      getFileSystem().mkdirs(keepParent);
 
       S3GuardTool.Prune cmd = new S3GuardTool.Prune(cmdConf);
       cmd.setMetadataStore(ms);
 
       createFile(new Path(parent, "stale"), true, true);
+      createFile(new Path(keepParent, "stale-to-keep"), true, true);
       Thread.sleep(TimeUnit.SECONDS.toMillis(2));
       createFile(new Path(parent, "fresh"), true, true);
 
       assertMetastoreListingCount(parent, "Children count before pruning", 2);
       exec(cmd, args);
       assertMetastoreListingCount(parent, "Pruned children count", 1);
+      assertMetastoreListingCount(keepParent,
+          "This child should have been kept (prefix restriction).", 1);
     } finally {
       getFileSystem().delete(parent, true);
       ms.prune(Long.MAX_VALUE);
@@ -213,17 +217,18 @@ public abstract class AbstractS3GuardToolTestBase extends AbstractS3ATestBase {
 
   @Test
   public void testPruneCommandCLI() throws Exception {
-    String testPath = path("testPruneCommandCLI").toString();
-    testPruneCommand(getFileSystem().getConf(),
-        "prune", "-seconds", "1", testPath);
+    Path testPath = path("testPruneCommandCLI");
+    testPruneCommand(getFileSystem().getConf(), testPath,
+        "prune", "-seconds", "1", testPath.toString());
   }
 
   @Test
   public void testPruneCommandConf() throws Exception {
     getConfiguration().setLong(Constants.S3GUARD_CLI_PRUNE_AGE,
         TimeUnit.SECONDS.toMillis(1));
-    String testPath = path("testPruneCommandConf").toString();
-    testPruneCommand(getConfiguration(), "prune", testPath);
+    Path testPath = path("testPruneCommandConf");
+    testPruneCommand(getConfiguration(), testPath,
+        "prune", testPath.toString());
   }
 
   @Test