/*
* 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;
import com.amazonaws.AmazonClientException;
import com.amazonaws.services.s3.model.ListObjectsRequest;
import com.amazonaws.services.s3.model.ObjectListing;
import com.amazonaws.services.s3.model.S3ObjectSummary;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.LocatedFileStatus;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.fs.PathFilter;
import org.apache.hadoop.fs.RemoteIterator;
import org.slf4j.Logger;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import static org.apache.hadoop.fs.s3a.Constants.S3N_FOLDER_SUFFIX;
import static org.apache.hadoop.fs.s3a.S3AUtils.createFileStatus;
import static org.apache.hadoop.fs.s3a.S3AUtils.objectRepresentsDirectory;
import static org.apache.hadoop.fs.s3a.S3AUtils.stringify;
import static org.apache.hadoop.fs.s3a.S3AUtils.translateException;
/**
* Place for the S3A listing classes; keeps all the small classes under control.
*/
public class Listing {
private final S3AFileSystem owner;
private static final Logger LOG = S3AFileSystem.LOG;
public Listing(S3AFileSystem owner) {
this.owner = owner;
}
/**
* Create a FileStatus iterator against a path, with a given
* list object request.
* @param listPath path of the listing
* @param request initial request to make
* @param filter the filter on which paths to accept
* @param acceptor the class/predicate to decide which entries to accept
* in the listing based on the full file status.
* @return the iterator
* @throws IOException IO Problems
*/
FileStatusListingIterator createFileStatusListingIterator(
Path listPath,
ListObjectsRequest request,
PathFilter filter,
Listing.FileStatusAcceptor acceptor) throws IOException {
return new FileStatusListingIterator(
new ObjectListingIterator(listPath, request),
filter,
acceptor);
}
/**
* Create a located status iterator over a file status iterator.
* @param statusIterator an iterator over the remote status entries
* @return a new remote iterator
*/
LocatedFileStatusIterator createLocatedFileStatusIterator(
RemoteIterator<FileStatus> statusIterator) {
return new LocatedFileStatusIterator(statusIterator);
}
/**
* Interface to implement by the logic deciding whether to accept a summary
* entry or path as a valid file or directory.
*/
interface FileStatusAcceptor {
/**
* Predicate to decide whether or not to accept a summary entry.
* @param keyPath qualified path to the entry
* @param summary summary entry
* @return true if the entry is accepted (i.e. that a status entry
* should be generated.
*/
boolean accept(Path keyPath, S3ObjectSummary summary);
/**
* Predicate to decide whether or not to accept a prefix.
* @param keyPath qualified path to the entry
* @param commonPrefix the prefix
* @return true if the entry is accepted (i.e. that a status entry
* should be generated.)
*/
boolean accept(Path keyPath, String commonPrefix);
}
/**
* A remote iterator which only iterates over a single `LocatedFileStatus`
* value.
*
* If the status value is null, the iterator declares that it has no data.
* This iterator is used to handle {@link listStatus()} calls where the path
* handed in refers to a file, not a directory: this is the iterator
* returned.
*/
static final class SingleStatusRemoteIterator
implements RemoteIterator<LocatedFileStatus> {
/**
* The status to return; set to null after the first iteration.
*/
private LocatedFileStatus status;
/**
* Constructor.
* @param status status value: may be null, in which case
* the iterator is empty.
*/
public SingleStatusRemoteIterator(LocatedFileStatus status) {
this.status = status;
}
/**
* {@inheritDoc}
* @return true if there is a file status to return: this is always false
* for the second iteration, and may be false for the first.
* @throws IOException never
*/
@Override
public boolean hasNext() throws IOException {
return status != null;
}
/**
* {@inheritDoc}
* @return the non-null status element passed in when the instance was
* constructed, if it ha not already been retrieved.
* @throws IOException never
* @throws NoSuchElementException if this is the second call, or it is
* the first call and a null {@link LocatedFileStatus} entry was passed
* to the constructor.
*/
@Override
public LocatedFileStatus next() throws IOException {
if (hasNext()) {
LocatedFileStatus s = this.status;
status = null;
return s;
} else {
throw new NoSuchElementException();
}
}
}
/**
* Wraps up object listing into a remote iterator which will ask for more
* listing data if needed.
*
* This is a complex operation, especially the process to determine
* if there are more entries remaining. If there are no more results
* remaining in the (filtered) results of the current listing request, then
* another request is made <i>and those results filtered</i> before the
* iterator can declare that there is more data available.
*
* The need to filter the results precludes the iterator from simply
* declaring that if the {@link S3AFileSystem.ObjectListingIterator#hasNext()}
* is true then there are more results. Instead the next batch of results must
* be retrieved and filtered.
*
* What does this mean? It means that remote requests to retrieve new
* batches of object listings are made in the {@link #hasNext()} call;
* the {@link #next()} call simply returns the filtered results of the last
* listing processed. However, do note that {@link #next()} calls
* {@link #hasNext()} during its operation. This is critical to ensure
* that a listing obtained through a sequence of {@link #next()} will
* complete with the same set of results as a classic
* {@code while(it.hasNext()} loop.
*
* Thread safety: None.
*/
class FileStatusListingIterator
implements RemoteIterator<FileStatus> {
/** Source of objects. */
private final ObjectListingIterator source;
/** Filter of paths from API call. */
private final PathFilter filter;
/** Filter of entries from file status. */
private final FileStatusAcceptor acceptor;
/** request batch size. */
private int batchSize;
/** Iterator over the current set of results. */
private ListIterator<FileStatus> statusBatchIterator;
/**
* Create an iterator over file status entries.
* @param source the listing iterator from a listObjects call.
* @param filter the filter on which paths to accept
* @param acceptor the class/predicate to decide which entries to accept
* in the listing based on the full file status.
* @throws IOException IO Problems
*/
FileStatusListingIterator(ObjectListingIterator source,
PathFilter filter,
FileStatusAcceptor acceptor) throws IOException {
this.source = source;
this.filter = filter;
this.acceptor = acceptor;
// build the first set of results. This will not trigger any
// remote IO, assuming the source iterator is in its initial
// iteration
requestNextBatch();
}
/**
* Report whether or not there is new data available.
* If there is data in the local filtered list, return true.
* Else: request more data util that condition is met, or there
* is no more remote listing data.
* @return true if a call to {@link #next()} will succeed.
* @throws IOException
*/
@Override
public boolean hasNext() throws IOException {
return statusBatchIterator.hasNext() || requestNextBatch();
}
@Override
public FileStatus next() throws IOException {
if (!hasNext()) {
throw new NoSuchElementException();
}
return statusBatchIterator.next();
}
/**
* Try to retrieve another batch.
* Note that for the initial batch,
* {@link S3AFileSystem.ObjectListingIterator} does not generate a request;
* it simply returns the initial set.
*
* @return true if a new batch was created.
* @throws IOException IO problems
*/
private boolean requestNextBatch() throws IOException {
// look for more object listing batches being available
while (source.hasNext()) {
// if available, retrieve it and build the next status
if (buildNextStatusBatch(source.next())) {
// this batch successfully generated entries matching the filters/
// acceptors; declare that the request was successful
return true;
} else {
LOG.debug("All entries in batch were filtered...continuing");
}
}
// if this code is reached, it means that all remaining
// object lists have been retrieved, and there are no new entries
// to return.
return false;
}
/**
* Build the next status batch from a listing.
* @param objects the next object listing
* @return true if this added any entries after filtering
*/
private boolean buildNextStatusBatch(ObjectListing objects) {
// counters for debug logs
int added = 0, ignored = 0;
// list to fill in with results. Initial size will be list maximum.
List<FileStatus> stats = new ArrayList<>(
objects.getObjectSummaries().size() +
objects.getCommonPrefixes().size());
// objects
for (S3ObjectSummary summary : objects.getObjectSummaries()) {
String key = summary.getKey();
Path keyPath = owner.keyToQualifiedPath(key);
if (LOG.isDebugEnabled()) {
LOG.debug("{}: {}", keyPath, stringify(summary));
}
// Skip over keys that are ourselves and old S3N _$folder$ files
if (acceptor.accept(keyPath, summary) && filter.accept(keyPath)) {
FileStatus status = createFileStatus(keyPath, summary,
owner.getDefaultBlockSize(keyPath), owner.getUsername());
LOG.debug("Adding: {}", status);
stats.add(status);
added++;
} else {
LOG.debug("Ignoring: {}", keyPath);
ignored++;
}
}
// prefixes: always directories
for (String prefix : objects.getCommonPrefixes()) {
Path keyPath = owner.keyToQualifiedPath(prefix);
if (acceptor.accept(keyPath, prefix) && filter.accept(keyPath)) {
FileStatus status = new S3AFileStatus(false, keyPath,
owner.getUsername());
LOG.debug("Adding directory: {}", status);
added++;
stats.add(status);
} else {
LOG.debug("Ignoring directory: {}", keyPath);
ignored++;
}
}
// finish up
batchSize = stats.size();
statusBatchIterator = stats.listIterator();
boolean hasNext = statusBatchIterator.hasNext();
LOG.debug("Added {} entries; ignored {}; hasNext={}; hasMoreObjects={}",
added, ignored, hasNext, objects.isTruncated());
return hasNext;
}
/**
* Get the number of entries in the current batch.
* @return a number, possibly zero.
*/
public int getBatchSize() {
return batchSize;
}
}
/**
* Wraps up AWS `ListObjects` requests in a remote iterator
* which will ask for more listing data if needed.
*
* That is:
*
* 1. The first invocation of the {@link #next()} call will return the results
* of the first request, the one created during the construction of the
* instance.
*
* 2. Second and later invocations will continue the ongoing listing,
* calling {@link #continueListObjects(ObjectListing)} to request the next
* batch of results.
*
* 3. The {@link #hasNext()} predicate returns true for the initial call,
* where {@link #next()} will return the initial results. It declares
* that it has future results iff the last executed request was truncated.
*
* Thread safety: none.
*/
class ObjectListingIterator implements RemoteIterator<ObjectListing> {
/** The path listed. */
private final Path listPath;
/** The most recent listing results. */
private ObjectListing objects;
/** Indicator that this is the first listing. */
private boolean firstListing = true;
/**
* Count of how many listings have been requested
* (including initial result).
*/
private int listingCount = 1;
/**
* Maximum keys in a request.
*/
private int maxKeys;
/**
* Constructor -calls `listObjects()` on the request to populate the
* initial set of results/fail if there was a problem talking to the bucket.
* @param listPath path of the listing
* @param request initial request to make
* */
ObjectListingIterator(
Path listPath,
ListObjectsRequest request) {
this.listPath = listPath;
this.maxKeys = owner.getMaxKeys();
this.objects = owner.listObjects(request);
}
/**
* Declare that the iterator has data if it is either is the initial
* iteration or it is a later one and the last listing obtained was
* incomplete.
* @throws IOException never: there is no IO in this operation.
*/
@Override
public boolean hasNext() throws IOException {
return firstListing || objects.isTruncated();
}
/**
* Ask for the next listing.
* For the first invocation, this returns the initial set, with no
* remote IO. For later requests, S3 will be queried, hence the calls
* may block or fail.
* @return the next object listing.
* @throws IOException if a query made of S3 fails.
* @throws NoSuchElementException if there is no more data to list.
*/
@Override
public ObjectListing next() throws IOException {
if (firstListing) {
// on the first listing, don't request more data.
// Instead just clear the firstListing flag so that it future calls
// will request new data.
firstListing = false;
} else {
try {
if (!objects.isTruncated()) {
// nothing more to request: fail.
throw new NoSuchElementException("No more results in listing of "
+ listPath);
}
// need to request a new set of objects.
LOG.debug("[{}], Requesting next {} objects under {}",
listingCount, maxKeys, listPath);
objects = owner.continueListObjects(objects);
listingCount++;
LOG.debug("New listing status: {}", this);
} catch (AmazonClientException e) {
throw translateException("listObjects()", listPath, e);
}
}
return objects;
}
@Override
public String toString() {
return "Object listing iterator against " + listPath
+ "; listing count "+ listingCount
+ "; isTruncated=" + objects.isTruncated();
}
/**
* Get the path listed.
* @return the path used in this listing.
*/
public Path getListPath() {
return listPath;
}
/**
* Get the count of listing requests.
* @return the counter of requests made (including the initial lookup).
*/
public int getListingCount() {
return listingCount;
}
}
/**
* Accept all entries except the base path and those which map to S3N
* pseudo directory markers.
*/
static class AcceptFilesOnly implements FileStatusAcceptor {
private final Path qualifiedPath;
public AcceptFilesOnly(Path qualifiedPath) {
this.qualifiedPath = qualifiedPath;
}
/**
* Reject a summary entry if the key path is the qualified Path, or
* it ends with {@code "_$folder$"}.
* @param keyPath key path of the entry
* @param summary summary entry
* @return true if the entry is accepted (i.e. that a status entry
* should be generated.
*/
@Override
public boolean accept(Path keyPath, S3ObjectSummary summary) {
return !keyPath.equals(qualifiedPath)
&& !summary.getKey().endsWith(S3N_FOLDER_SUFFIX)
&& !objectRepresentsDirectory(summary.getKey(), summary.getSize());
}
/**
* Accept no directory paths.
* @param keyPath qualified path to the entry
* @param prefix common prefix in listing.
* @return false, always.
*/
@Override
public boolean accept(Path keyPath, String prefix) {
return false;
}
}
/**
* Take a remote iterator over a set of {@link FileStatus} instances and
* return a remote iterator of {@link LocatedFileStatus} instances.
*/
class LocatedFileStatusIterator
implements RemoteIterator<LocatedFileStatus> {
private final RemoteIterator<FileStatus> statusIterator;
/**
* Constructor.
* @param statusIterator an iterator over the remote status entries
*/
LocatedFileStatusIterator(RemoteIterator<FileStatus> statusIterator) {
this.statusIterator = statusIterator;
}
@Override
public boolean hasNext() throws IOException {
return statusIterator.hasNext();
}
@Override
public LocatedFileStatus next() throws IOException {
return owner.toLocatedFileStatus(statusIterator.next());
}
}
/**
* Accept all entries except the base path and those which map to S3N
* pseudo directory markers.
*/
static class AcceptAllButSelfAndS3nDirs implements FileStatusAcceptor {
/** Base path. */
private final Path qualifiedPath;
/**
* Constructor.
* @param qualifiedPath an already-qualified path.
*/
public AcceptAllButSelfAndS3nDirs(Path qualifiedPath) {
this.qualifiedPath = qualifiedPath;
}
/**
* Reject a summary entry if the key path is the qualified Path, or
* it ends with {@code "_$folder$"}.
* @param keyPath key path of the entry
* @param summary summary entry
* @return true if the entry is accepted (i.e. that a status entry
* should be generated.)
*/
@Override
public boolean accept(Path keyPath, S3ObjectSummary summary) {
return !keyPath.equals(qualifiedPath) &&
!summary.getKey().endsWith(S3N_FOLDER_SUFFIX);
}
/**
* Accept all prefixes except the one for the base path, "self".
* @param keyPath qualified path to the entry
* @param prefix common prefix in listing.
* @return true if the entry is accepted (i.e. that a status entry
* should be generated.
*/
@Override
public boolean accept(Path keyPath, String prefix) {
return !keyPath.equals(qualifiedPath);
}
}
/**
* A Path filter which accepts all filenames.
*/
static final PathFilter ACCEPT_ALL = new PathFilter() {
@Override
public boolean accept(Path file) {
return true;
}
@Override
public String toString() {
return "ACCEPT_ALL";
}
};
}