| /* |
| * 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 |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * 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.hadoop.fs.s3a.s3guard; |
| |
| import java.io.IOException; |
| import java.util.ArrayList; |
| import java.util.Collection; |
| import java.util.HashSet; |
| import java.util.Iterator; |
| import java.util.LinkedList; |
| import java.util.Queue; |
| import java.util.Set; |
| |
| import com.google.common.base.Preconditions; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import org.apache.hadoop.classification.InterfaceAudience; |
| import org.apache.hadoop.classification.InterfaceStability; |
| import org.apache.hadoop.fs.FileStatus; |
| import org.apache.hadoop.fs.Path; |
| import org.apache.hadoop.fs.RemoteIterator; |
| |
| /** |
| * {@code MetadataStoreListFilesIterator} is a {@link RemoteIterator} that |
| * is similar to {@code DescendantsIterator} but does not return directories |
| * that have (or may have) children, and will also provide access to the set of |
| * tombstones to allow recently deleted S3 objects to be filtered out from a |
| * corresponding request. In other words, it returns tombstones and the same |
| * set of objects that should exist in S3: empty directories, and files, and not |
| * other directories whose existence is inferred therefrom. |
| * |
| * For example, assume the consistent store contains metadata representing this |
| * file system structure: |
| * |
| * <pre> |
| * /dir1 |
| * |-- dir2 |
| * | |-- file1 |
| * | `-- file2 |
| * `-- dir3 |
| * |-- dir4 |
| * | `-- file3 |
| * |-- dir5 |
| * | `-- file4 |
| * `-- dir6 |
| * </pre> |
| * |
| * Consider this code sample: |
| * <pre> |
| * final PathMetadata dir1 = get(new Path("/dir1")); |
| * for (MetadataStoreListFilesIterator files = |
| * new MetadataStoreListFilesIterator(dir1); files.hasNext(); ) { |
| * final FileStatus status = files.next().getFileStatus(); |
| * System.out.printf("%s %s%n", status.isDirectory() ? 'D' : 'F', |
| * status.getPath()); |
| * } |
| * </pre> |
| * |
| * The output is: |
| * <pre> |
| * F /dir1/dir2/file1 |
| * F /dir1/dir2/file2 |
| * F /dir1/dir3/dir4/file3 |
| * F /dir1/dir3/dir5/file4 |
| * D /dir1/dir3/dir6 |
| * </pre> |
| */ |
| @InterfaceAudience.Private |
| @InterfaceStability.Evolving |
| public class MetadataStoreListFilesIterator implements |
| RemoteIterator<FileStatus> { |
| public static final Logger LOG = LoggerFactory.getLogger( |
| MetadataStoreListFilesIterator.class); |
| |
| private final boolean allowAuthoritative; |
| private final MetadataStore metadataStore; |
| private final Set<Path> tombstones = new HashSet<>(); |
| private Iterator<FileStatus> leafNodesIterator = null; |
| |
| public MetadataStoreListFilesIterator(MetadataStore ms, PathMetadata meta, |
| boolean allowAuthoritative) throws IOException { |
| Preconditions.checkNotNull(ms); |
| this.metadataStore = ms; |
| this.allowAuthoritative = allowAuthoritative; |
| prefetch(meta); |
| } |
| |
| private void prefetch(PathMetadata meta) throws IOException { |
| final Queue<PathMetadata> queue = new LinkedList<>(); |
| final Collection<FileStatus> leafNodes = new ArrayList<>(); |
| |
| if (meta != null) { |
| final Path path = meta.getFileStatus().getPath(); |
| if (path.isRoot()) { |
| DirListingMetadata rootListing = metadataStore.listChildren(path); |
| if (rootListing != null) { |
| tombstones.addAll(rootListing.listTombstones()); |
| queue.addAll(rootListing.withoutTombstones().getListing()); |
| } |
| } else { |
| queue.add(meta); |
| } |
| } |
| |
| while(!queue.isEmpty()) { |
| PathMetadata nextMetadata = queue.poll(); |
| FileStatus nextStatus = nextMetadata.getFileStatus(); |
| if (nextStatus.isFile()) { |
| // All files are leaf nodes by definition |
| leafNodes.add(nextStatus); |
| continue; |
| } |
| if (nextStatus.isDirectory()) { |
| final Path path = nextStatus.getPath(); |
| DirListingMetadata children = metadataStore.listChildren(path); |
| if (children != null) { |
| tombstones.addAll(children.listTombstones()); |
| Collection<PathMetadata> liveChildren = |
| children.withoutTombstones().getListing(); |
| if (!liveChildren.isEmpty()) { |
| // If it's a directory, has children, not all deleted, then we |
| // add the children to the queue and move on to the next node |
| queue.addAll(liveChildren); |
| continue; |
| } else if (allowAuthoritative && children.isAuthoritative()) { |
| leafNodes.add(nextStatus); |
| } |
| } |
| } |
| // Directories that *might* be empty are ignored for now, since we |
| // cannot confirm that they are empty without incurring other costs. |
| // Users of this class can still discover empty directories via S3's |
| // fake directories, subject to the same consistency semantics as before. |
| // The only other possibility is a symlink, which is unsupported on S3A. |
| } |
| leafNodesIterator = leafNodes.iterator(); |
| } |
| |
| @Override |
| public boolean hasNext() { |
| return leafNodesIterator.hasNext(); |
| } |
| |
| @Override |
| public FileStatus next() { |
| return leafNodesIterator.next(); |
| } |
| |
| public Set<Path> listTombstones() { |
| return tombstones; |
| } |
| } |