hadoop Listing 源码
haddop Listing 代码
文件路径：/hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/Listing.java
/*
* 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.services.s3.model.S3ObjectSummary;
import org.apache.hadoop.classification.InterfaceAudience;
import org.apache.hadoop.classification.VisibleForTesting;
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.apache.hadoop.fs.s3a.impl.AbstractStoreOperation;
import org.apache.hadoop.fs.s3a.impl.ListingOperationCallbacks;
import org.apache.hadoop.fs.s3a.impl.StoreContext;
import org.apache.hadoop.fs.statistics.IOStatistics;
import org.apache.hadoop.fs.statistics.IOStatisticsAggregator;
import org.apache.hadoop.fs.statistics.IOStatisticsSource;
import org.apache.hadoop.fs.statistics.IOStatisticsContext;
import org.apache.hadoop.fs.statistics.impl.IOStatisticsStore;
import org.apache.hadoop.fs.store.audit.AuditSpan;
import org.apache.hadoop.util.functional.RemoteIterators;
import org.slf4j.Logger;
import java.io.Closeable;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import java.util.concurrent.CompletableFuture;
import java.util.StringJoiner;
import static org.apache.hadoop.fs.s3a.Constants.S3N_FOLDER_SUFFIX;
import static org.apache.hadoop.fs.s3a.Invoker.onceInTheFuture;
import static org.apache.hadoop.fs.s3a.S3AUtils.ACCEPT_ALL;
import static org.apache.hadoop.fs.s3a.S3AUtils.createFileStatus;
import static org.apache.hadoop.fs.s3a.S3AUtils.maybeAddTrailingSlash;
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.auth.RoleModel.pathToKey;
import static org.apache.hadoop.fs.statistics.StoreStatisticNames.OBJECT_CONTINUE_LIST_REQUEST;
import static org.apache.hadoop.fs.statistics.StoreStatisticNames.OBJECT_LIST_REQUEST;
import static org.apache.hadoop.fs.statistics.impl.IOStatisticsBinding.iostatisticsStore;
import static org.apache.hadoop.util.functional.RemoteIterators.filteringRemoteIterator;
import static org.apache.hadoop.util.functional.RemoteIterators.remoteIteratorFromArray;
import static org.apache.hadoop.util.functional.RemoteIterators.remoteIteratorFromSingleton;
/**
* Place for the S3A listing classes; keeps all the small classes under control.
*
* Spans passed in are attached to the listing iterators returned, but are not
* closed at the end of the iteration. This is because the same span
*/
@InterfaceAudience.Private
public class Listing extends AbstractStoreOperation {
private static final Logger LOG = S3AFileSystem.LOG;
private final boolean isCSEEnabled;
static final FileStatusAcceptor ACCEPT_ALL_BUT_S3N =
new AcceptAllButS3nDirs();
private final ListingOperationCallbacks listingOperationCallbacks;
public Listing(ListingOperationCallbacks listingOperationCallbacks,
StoreContext storeContext) {
super(storeContext);
this.listingOperationCallbacks = listingOperationCallbacks;
this.isCSEEnabled = storeContext.isCSEEnabled();
}
/**
* Create a FileStatus iterator against a provided list of file status, with
* a given status filter.
*
* @param fileStatuses the provided list of file status. NO remote calls.
* @param filter file path filter on which paths to accept
* @param acceptor the file status acceptor
* @return the file status iterator
*/
RemoteIterator<S3AFileStatus> createProvidedFileStatusIterator(
S3AFileStatus[] fileStatuses,
PathFilter filter,
FileStatusAcceptor acceptor) {
return filteringRemoteIterator(
remoteIteratorFromArray(fileStatuses),
status ->
filter.accept(status.getPath()) && acceptor.accept(status));
}
/**
* Create a FileStatus iterator against a provided list of file status.
* @param fileStatuses array of file status.
* @return the file status iterator.
*/
@VisibleForTesting
public static RemoteIterator<S3AFileStatus> toProvidedFileStatusIterator(
S3AFileStatus[] fileStatuses) {
return filteringRemoteIterator(
remoteIteratorFromArray(fileStatuses),
Listing.ACCEPT_ALL_BUT_S3N::accept);
}
/**
* 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.
* @param span audit span for this iterator
* @return the iterator
* @throws IOException IO Problems
*/
@Retries.RetryRaw
public FileStatusListingIterator createFileStatusListingIterator(
Path listPath,
S3ListRequest request,
PathFilter filter,
FileStatusAcceptor acceptor,
AuditSpan span) throws IOException {
return new FileStatusListingIterator(
createObjectListingIterator(listPath, request, span),
filter,
acceptor);
}
/**
* Create an object listing iterator against a path, with a given
* list object request.
* @param listPath path of the listing
* @param request initial request to make
* @param span audit span for this iterator
* @return the iterator
* @throws IOException IO Problems
*/
@Retries.RetryRaw
private ObjectListingIterator createObjectListingIterator(
final Path listPath,
final S3ListRequest request,
final AuditSpan span) throws IOException {
return new ObjectListingIterator(listPath, request, span);
}
/**
* Create a located status iterator over a file status iterator.
* @param statusIterator an iterator over the remote status entries
* @return a new remote iterator
*/
@VisibleForTesting
public RemoteIterator<S3ALocatedFileStatus> createLocatedFileStatusIterator(
RemoteIterator<S3AFileStatus> statusIterator) {
return RemoteIterators.mappingRemoteIterator(
statusIterator,
listingOperationCallbacks::toLocatedFileStatus);
}
/**
* Create a remote iterator from a single status entry.
* @param status status
* @return iterator.
*/
public RemoteIterator<S3ALocatedFileStatus> createSingleStatusIterator(
S3ALocatedFileStatus status) {
return remoteIteratorFromSingleton(status);
}
/**
* List files under a path assuming the path to be a directory.
* @param path input path.
* @param recursive recursive listing?
* @param acceptor file status filter
* @param span audit span for this iterator
* @return an iterator over listing.
* @throws IOException any exception.
*/
public RemoteIterator<S3ALocatedFileStatus> getListFilesAssumingDir(
Path path,
boolean recursive, FileStatusAcceptor acceptor,
AuditSpan span) throws IOException {
String key = maybeAddTrailingSlash(pathToKey(path));
String delimiter = recursive ? null : "/";
if (recursive) {
LOG.debug("Recursive list of all entries under {}", key);
} else {
LOG.debug("Requesting all entries under {} with delimiter '{}'",
key, delimiter);
}
return createLocatedFileStatusIterator(
createFileStatusListingIterator(path,
listingOperationCallbacks
.createListObjectsRequest(key,
delimiter,
span),
ACCEPT_ALL,
acceptor,
span));
}
/**
* Generate list located status for a directory.
* @param dir directory to check.
* @param filter a path filter.
* @param span audit span for this iterator
* @return an iterator that traverses statuses of the given dir.
* @throws IOException in case of failure.
*/
public RemoteIterator<S3ALocatedFileStatus> getLocatedFileStatusIteratorForDir(
Path dir, PathFilter filter, AuditSpan span) throws IOException {
span.activate();
final String key = maybeAddTrailingSlash(pathToKey(dir));
return createLocatedFileStatusIterator(
createFileStatusListingIterator(dir,
listingOperationCallbacks
.createListObjectsRequest(key, "/", span),
filter,
new AcceptAllButSelfAndS3nDirs(dir),
span));
}
/**
* Calculate list of file statuses assuming path
* to be a non-empty directory.
* @param path input path.
* @param span audit span for this iterator
* @return iterator of file statuses.
* @throws IOException Any IO problems.
*/
@Retries.RetryRaw
public RemoteIterator<S3AFileStatus>
getFileStatusesAssumingNonEmptyDir(Path path, final AuditSpan span)
throws IOException {
String key = pathToKey(path);
if (!key.isEmpty()) {
key = key + '/';
}
S3ListRequest request = createListObjectsRequest(key, "/", span);
LOG.debug("listStatus: doing listObjects for directory {}", key);
// return the results obtained from s3.
return createFileStatusListingIterator(
path,
request,
ACCEPT_ALL,
new AcceptAllButSelfAndS3nDirs(path),
span);
}
public S3ListRequest createListObjectsRequest(String key,
String delimiter,
final AuditSpan span) {
return listingOperationCallbacks.createListObjectsRequest(key, delimiter,
span);
}
/**
* 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);
/**
* Predicate to decide whether or not to accept a file status.
* @param status file status containing file path information
* @return true if the status is accepted else false
*/
boolean accept(FileStatus status);
}
/**
* 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 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<S3AFileStatus>, IOStatisticsSource, Closeable {
/** 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<S3AFileStatus> 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
*/
@Retries.RetryTranslated
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.
* Lastly, return true if the {@code providedStatusIterator}
* has left items.
* @return true if a call to {@link #next()} will succeed.
* @throws IOException IO Problems
*/
@Override
@Retries.RetryTranslated
public boolean hasNext() throws IOException {
return sourceHasNext();
}
@Retries.RetryTranslated
private boolean sourceHasNext() throws IOException {
return statusBatchIterator.hasNext() || requestNextBatch();
}
@Override
@Retries.RetryTranslated
public S3AFileStatus next() throws IOException {
final S3AFileStatus status;
if (sourceHasNext()) {
status = statusBatchIterator.next();
} else {
throw new NoSuchElementException();
}
return status;
}
/**
* Close, if called, will update
* the thread statistics context with the value.
*/
@Override
public void close() {
source.close();
}
/**
* Try to retrieve another batch.
* Note that for the initial batch,
* {@link ObjectListingIterator} does not generate a request;
* it simply returns the initial set.
*
* @return true if a new batch was created.
* @throws IOException IO problems
*/
@Retries.RetryTranslated
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(S3ListResult objects) {
// counters for debug logs
int added = 0, ignored = 0;
// list to fill in with results. Initial size will be list maximum.
List<S3AFileStatus> stats = new ArrayList<>(
objects.getObjectSummaries().size() +
objects.getCommonPrefixes().size());
// objects
for (S3ObjectSummary summary : objects.getObjectSummaries()) {
String key = summary.getKey();
Path keyPath = getStoreContext().getContextAccessors().keyToPath(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)) {
S3AFileStatus status = createFileStatus(keyPath, summary,
listingOperationCallbacks.getDefaultBlockSize(keyPath),
getStoreContext().getUsername(),
summary.getETag(), null, isCSEEnabled);
LOG.debug("Adding: {}", status);
stats.add(status);
added++;
} else {
LOG.debug("Ignoring: {}", keyPath);
ignored++;
}
}
// prefixes: always directories
for (String prefix : objects.getCommonPrefixes()) {
Path keyPath = getStoreContext()
.getContextAccessors()
.keyToPath(prefix);
if (acceptor.accept(keyPath, prefix) && filter.accept(keyPath)) {
S3AFileStatus status = new S3AFileStatus(Tristate.FALSE, keyPath,
getStoreContext().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;
}
/**
* Return any IOStatistics provided by the underlying stream.
* @return IO stats from the inner stream.
*/
@Override
public IOStatistics getIOStatistics() {
return source.getIOStatistics();
}
@Override
public String toString() {
return new StringJoiner(", ",
FileStatusListingIterator.class.getSimpleName() + "[", "]")
.add(source.toString())
.toString();
}
}
/**
* 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 S3AFileSystem#continueListObjects} 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<S3ListResult>,
IOStatisticsSource, Closeable {
/** The path listed. */
private final Path listPath;
private final AuditSpan span;
/**
* Context statistics aggregator.
*/
private final IOStatisticsAggregator aggregator;
/** The most recent listing results. */
private S3ListResult objects;
/** The most recent listing request. */
private S3ListRequest request;
/** 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;
private final IOStatisticsStore iostats;
/**
* Future to store current batch listing result.
*/
private CompletableFuture<S3ListResult> s3ListResultFuture;
/**
* Result of previous batch.
*/
private S3ListResult objectsPrev;
/**
* 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
* @param span audit span for this iterator.
* @throws IOException if listObjects raises one.
*/
@Retries.RetryRaw
ObjectListingIterator(
Path listPath,
S3ListRequest request,
AuditSpan span) throws IOException {
this.listPath = listPath;
this.maxKeys = listingOperationCallbacks.getMaxKeys();
this.request = request;
this.objectsPrev = null;
this.iostats = iostatisticsStore()
.withDurationTracking(OBJECT_LIST_REQUEST)
.withDurationTracking(OBJECT_CONTINUE_LIST_REQUEST)
.build();
this.span = span;
this.s3ListResultFuture = listingOperationCallbacks
.listObjectsAsync(request, iostats, span);
this.aggregator = IOStatisticsContext.getCurrentIOStatisticsContext()
.getAggregator();
}
/**
* 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 ||
(objectsPrev != null && objectsPrev.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
@Retries.RetryTranslated
public S3ListResult next() throws IOException {
if (firstListing) {
// clear the firstListing flag for future calls.
firstListing = false;
// Calculating the result of last async list call.
objects = onceInTheFuture("listObjects()", listPath.toString(), s3ListResultFuture);
fetchNextBatchAsyncIfPresent();
} else {
if (objectsPrev!= null && !objectsPrev.isTruncated()) {
// nothing more to request: fail.
throw new NoSuchElementException("No more results in listing of "
+ listPath);
}
// Calculating the result of last async list call.
objects = onceInTheFuture("listObjects()", listPath.toString(), s3ListResultFuture);
// Requesting next batch of results.
fetchNextBatchAsyncIfPresent();
listingCount++;
LOG.debug("New listing status: {}", this);
}
// Storing the current result to be used by hasNext() call.
objectsPrev = objects;
return objectsPrev;
}
/**
* If there are more listings present, call for next batch async.
*/
private void fetchNextBatchAsyncIfPresent() {
if (objects.isTruncated()) {
LOG.debug("[{}], Requesting next {} objects under {}",
listingCount, maxKeys, listPath);
s3ListResultFuture = listingOperationCallbacks
.continueListObjectsAsync(request, objects, iostats, span);
}
}
@Override
public String toString() {
return "Object listing iterator against " + listPath
+ "; listing count "+ listingCount
+ "; isTruncated=" + objects.isTruncated()
+ "; " + iostats;
}
@Override
public IOStatistics getIOStatistics() {
return iostats;
}
/**
* 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;
}
/**
* Close, if called, will update
* the thread statistics context with the value.
*/
@Override
public void close() {
aggregator.aggregate(getIOStatistics());
}
}
/**
* 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());
}
/**
* 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;
}
@Override
public boolean accept(FileStatus status) {
return (status != null) && status.isFile();
}
}
/**
* Accept all entries except those which map to S3N pseudo directory markers.
*/
static class AcceptAllButS3nDirs implements FileStatusAcceptor {
public boolean accept(Path keyPath, S3ObjectSummary summary) {
return !summary.getKey().endsWith(S3N_FOLDER_SUFFIX);
}
public boolean accept(Path keyPath, String prefix) {
return !keyPath.toString().endsWith(S3N_FOLDER_SUFFIX);
}
public boolean accept(FileStatus status) {
return !status.getPath().toString().endsWith(S3N_FOLDER_SUFFIX);
}
}
/**
* Accept all entries except the base path and those which map to S3N
* pseudo directory markers.
*/
public 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);
}
@Override
public boolean accept(FileStatus status) {
return (status != null) && !status.getPath().equals(qualifiedPath);
}
}
@SuppressWarnings("unchecked")
public static RemoteIterator<LocatedFileStatus> toLocatedFileStatusIterator(
RemoteIterator<? extends LocatedFileStatus> iterator) {
return (RemoteIterator < LocatedFileStatus >) iterator;
}
}
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