package org.apache.lucene.index;
/*
* 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.
*/
import java.io.Closeable;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.nio.file.NoSuchFileException;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.regex.Matcher;
import org.apache.lucene.store.Directory;
import org.apache.lucene.store.NoSuchDirectoryException;
import org.apache.lucene.util.CollectionUtil;
import org.apache.lucene.util.InfoStream;
/*
* This class keeps track of each SegmentInfos instance that
* is still "live", either because it corresponds to a
* segments_N file in the Directory (a "commit", i.e. a
* committed SegmentInfos) or because it's an in-memory
* SegmentInfos that a writer is actively updating but has
* not yet committed. This class uses simple reference
* counting to map the live SegmentInfos instances to
* individual files in the Directory.
*
* The same directory file may be referenced by more than
* one IndexCommit, i.e. more than one SegmentInfos.
* Therefore we count how many commits reference each file.
* When all the commits referencing a certain file have been
* deleted, the refcount for that file becomes zero, and the
* file is deleted.
*
* A separate deletion policy interface
* (IndexDeletionPolicy) is consulted on creation (onInit)
* and once per commit (onCommit), to decide when a commit
* should be removed.
*
* It is the business of the IndexDeletionPolicy to choose
* when to delete commit points. The actual mechanics of
* file deletion, retrying, etc, derived from the deletion
* of commit points is the business of the IndexFileDeleter.
*
* The current default deletion policy is {@link
* KeepOnlyLastCommitDeletionPolicy}, which removes all
* prior commits when a new commit has completed. This
* matches the behavior before 2.2.
*
* Note that you must hold the write.lock before
* instantiating this class. It opens segments_N file(s)
* directly with no retry logic.
*/
final class IndexFileDeleter implements Closeable {
/* Files that we tried to delete but failed (likely
* because they are open and we are running on Windows),
* so we will retry them again later: */
private List<String> deletable;
/* Reference count for all files in the index.
* Counts how many existing commits reference a file.
**/
private Map<String, RefCount> refCounts = new HashMap<>();
/* Holds all commits (segments_N) currently in the index.
* This will have just 1 commit if you are using the
* default delete policy (KeepOnlyLastCommitDeletionPolicy).
* Other policies may leave commit points live for longer
* in which case this list would be longer than 1: */
private List<CommitPoint> commits = new ArrayList<>();
/* Holds files we had incref'd from the previous
* non-commit checkpoint: */
private final List<String> lastFiles = new ArrayList<>();
/* Commits that the IndexDeletionPolicy have decided to delete: */
private List<CommitPoint> commitsToDelete = new ArrayList<>();
private final InfoStream infoStream;
private Directory directory;
private IndexDeletionPolicy policy;
final boolean startingCommitDeleted;
private SegmentInfos lastSegmentInfos;
/** Change to true to see details of reference counts when
* infoStream is enabled */
public static boolean VERBOSE_REF_COUNTS = false;
// Used only for assert
private final IndexWriter writer;
// called only from assert
private boolean locked() {
return writer == null || Thread.holdsLock(writer);
}
/**
* Initialize the deleter: find all previous commits in
* the Directory, incref the files they reference, call
* the policy to let it delete commits. This will remove
* any files not referenced by any of the commits.
* @throws IOException if there is a low-level IO error
*/
public IndexFileDeleter(Directory directory, IndexDeletionPolicy policy, SegmentInfos segmentInfos,
InfoStream infoStream, IndexWriter writer, boolean initialIndexExists) throws IOException {
this.infoStream = infoStream;
this.writer = writer;
final String currentSegmentsFile = segmentInfos.getSegmentsFileName();
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "init: current segments file is \"" + currentSegmentsFile + "\"; deletionPolicy=" + policy);
}
this.policy = policy;
this.directory = directory;
// First pass: walk the files and initialize our ref
// counts:
long currentGen = segmentInfos.getGeneration();
CommitPoint currentCommitPoint = null;
String[] files = null;
try {
files = directory.listAll();
} catch (NoSuchDirectoryException e) {
// it means the directory is empty, so ignore it.
files = new String[0];
}
if (currentSegmentsFile != null) {
Matcher m = IndexFileNames.CODEC_FILE_PATTERN.matcher("");
for (String fileName : files) {
m.reset(fileName);
if (!fileName.endsWith("write.lock") && !fileName.equals(IndexFileNames.SEGMENTS_GEN)
&& (m.matches() || fileName.startsWith(IndexFileNames.SEGMENTS))) {
// Add this file to refCounts with initial count 0:
getRefCount(fileName);
if (fileName.startsWith(IndexFileNames.SEGMENTS)) {
// This is a commit (segments or segments_N), and
// it's valid (<= the max gen). Load it, then
// incref all files it refers to:
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "init: load commit \"" + fileName + "\"");
}
SegmentInfos sis = new SegmentInfos();
try {
sis.read(directory, fileName);
} catch (FileNotFoundException | NoSuchFileException e) {
// LUCENE-948: on NFS (and maybe others), if
// you have writers switching back and forth
// between machines, it's very likely that the
// dir listing will be stale and will claim a
// file segments_X exists when in fact it
// doesn't. So, we catch this and handle it
// as if the file does not exist
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "init: hit FileNotFoundException when loading commit \"" + fileName + "\"; skipping this commit point");
}
sis = null;
} catch (IOException e) {
if (SegmentInfos.generationFromSegmentsFileName(fileName) <= currentGen && directory.fileLength(fileName) > 0) {
throw e;
} else {
// Most likely we are opening an index that
// has an aborted "future" commit, so suppress
// exc in this case
sis = null;
}
}
if (sis != null) {
final CommitPoint commitPoint = new CommitPoint(commitsToDelete, directory, sis);
if (sis.getGeneration() == segmentInfos.getGeneration()) {
currentCommitPoint = commitPoint;
}
commits.add(commitPoint);
incRef(sis, true);
if (lastSegmentInfos == null || sis.getGeneration() > lastSegmentInfos.getGeneration()) {
lastSegmentInfos = sis;
}
}
}
}
}
}
if (currentCommitPoint == null && currentSegmentsFile != null && initialIndexExists) {
// We did not in fact see the segments_N file
// corresponding to the segmentInfos that was passed
// in. Yet, it must exist, because our caller holds
// the write lock. This can happen when the directory
// listing was stale (eg when index accessed via NFS
// client with stale directory listing cache). So we
// try now to explicitly open this commit point:
SegmentInfos sis = new SegmentInfos();
try {
sis.read(directory, currentSegmentsFile);
} catch (IOException e) {
throw new CorruptIndexException("failed to locate current segments_N file \"" + currentSegmentsFile + "\"");
}
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "forced open of current segments file " + segmentInfos.getSegmentsFileName());
}
currentCommitPoint = new CommitPoint(commitsToDelete, directory, sis);
commits.add(currentCommitPoint);
incRef(sis, true);
}
// We keep commits list in sorted order (oldest to newest):
CollectionUtil.timSort(commits);
// Now delete anything with ref count at 0. These are
// presumably abandoned files eg due to crash of
// IndexWriter.
for(Map.Entry<String, RefCount> entry : refCounts.entrySet() ) {
RefCount rc = entry.getValue();
final String fileName = entry.getKey();
if (0 == rc.count) {
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "init: removing unreferenced file \"" + fileName + "\"");
}
deleteFile(fileName);
}
}
// Finally, give policy a chance to remove things on
// startup:
policy.onInit(commits);
// Always protect the incoming segmentInfos since
// sometime it may not be the most recent commit
checkpoint(segmentInfos, false);
startingCommitDeleted = currentCommitPoint == null ? false : currentCommitPoint.isDeleted();
deleteCommits();
}
public SegmentInfos getLastSegmentInfos() {
return lastSegmentInfos;
}
/**
* Remove the CommitPoints in the commitsToDelete List by
* DecRef'ing all files from each SegmentInfos.
*/
private void deleteCommits() throws IOException {
int size = commitsToDelete.size();
if (size > 0) {
// First decref all files that had been referred to by
// the now-deleted commits:
for(int i=0;i<size;i++) {
CommitPoint commit = commitsToDelete.get(i);
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "deleteCommits: now decRef commit \"" + commit.getSegmentsFileName() + "\"");
}
for (final String file : commit.files) {
decRef(file);
}
}
commitsToDelete.clear();
// Now compact commits to remove deleted ones (preserving the sort):
size = commits.size();
int readFrom = 0;
int writeTo = 0;
while(readFrom < size) {
CommitPoint commit = commits.get(readFrom);
if (!commit.deleted) {
if (writeTo != readFrom) {
commits.set(writeTo, commits.get(readFrom));
}
writeTo++;
}
readFrom++;
}
while(size > writeTo) {
commits.remove(size-1);
size--;
}
}
}
/**
* Writer calls this when it has hit an error and had to
* roll back, to tell us that there may now be
* unreferenced files in the filesystem. So we re-list
* the filesystem and delete such files. If segmentName
* is non-null, we will only delete files corresponding to
* that segment.
*/
public void refresh(String segmentName) throws IOException {
assert locked();
String[] files = directory.listAll();
String segmentPrefix1;
String segmentPrefix2;
if (segmentName != null) {
segmentPrefix1 = segmentName + ".";
segmentPrefix2 = segmentName + "_";
} else {
segmentPrefix1 = null;
segmentPrefix2 = null;
}
Matcher m = IndexFileNames.CODEC_FILE_PATTERN.matcher("");
for(int i=0;i<files.length;i++) {
String fileName = files[i];
m.reset(fileName);
if ((segmentName == null || fileName.startsWith(segmentPrefix1) || fileName.startsWith(segmentPrefix2)) &&
!fileName.endsWith("write.lock") &&
!refCounts.containsKey(fileName) &&
!fileName.equals(IndexFileNames.SEGMENTS_GEN) &&
(m.matches() || fileName.startsWith(IndexFileNames.SEGMENTS))) {
// Unreferenced file, so remove it
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "refresh [prefix=" + segmentName + "]: removing newly created unreferenced file \"" + fileName + "\"");
}
deleteFile(fileName);
}
}
}
public void refresh() throws IOException {
// Set to null so that we regenerate the list of pending
// files; else we can accumulate same file more than
// once
assert locked();
deletable = null;
refresh(null);
}
@Override
public void close() throws IOException {
// DecRef old files from the last checkpoint, if any:
assert locked();
if (!lastFiles.isEmpty()) {
decRef(lastFiles);
lastFiles.clear();
}
deletePendingFiles();
}
/**
* Revisits the {@link IndexDeletionPolicy} by calling its
* {@link IndexDeletionPolicy#onCommit(List)} again with the known commits.
* This is useful in cases where a deletion policy which holds onto index
* commits is used. The application may know that some commits are not held by
* the deletion policy anymore and call
* {@link IndexWriter#deleteUnusedFiles()}, which will attempt to delete the
* unused commits again.
*/
void revisitPolicy() throws IOException {
assert locked();
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "now revisitPolicy");
}
if (commits.size() > 0) {
policy.onCommit(commits);
deleteCommits();
}
}
public void deletePendingFiles() throws IOException {
assert locked();
if (deletable != null) {
List<String> oldDeletable = deletable;
deletable = null;
int size = oldDeletable.size();
for(int i=0;i<size;i++) {
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "delete pending file " + oldDeletable.get(i));
}
deleteFile(oldDeletable.get(i));
}
}
}
/**
* For definition of "check point" see IndexWriter comments:
* "Clarification: Check Points (and commits)".
*
* Writer calls this when it has made a "consistent
* change" to the index, meaning new files are written to
* the index and the in-memory SegmentInfos have been
* modified to point to those files.
*
* This may or may not be a commit (segments_N may or may
* not have been written).
*
* We simply incref the files referenced by the new
* SegmentInfos and decref the files we had previously
* seen (if any).
*
* If this is a commit, we also call the policy to give it
* a chance to remove other commits. If any commits are
* removed, we decref their files as well.
*/
public void checkpoint(SegmentInfos segmentInfos, boolean isCommit) throws IOException {
assert locked();
assert Thread.holdsLock(writer);
long t0 = 0;
if (infoStream.isEnabled("IFD")) {
t0 = System.nanoTime();
infoStream.message("IFD", "now checkpoint \"" + writer.segString(writer.toLiveInfos(segmentInfos)) + "\" [" + segmentInfos.size() + " segments " + "; isCommit = " + isCommit + "]");
}
// Try again now to delete any previously un-deletable
// files (because they were in use, on Windows):
deletePendingFiles();
// Incref the files:
incRef(segmentInfos, isCommit);
if (isCommit) {
// Append to our commits list:
commits.add(new CommitPoint(commitsToDelete, directory, segmentInfos));
// Tell policy so it can remove commits:
policy.onCommit(commits);
// Decref files for commits that were deleted by the policy:
deleteCommits();
} else {
// DecRef old files from the last checkpoint, if any:
decRef(lastFiles);
lastFiles.clear();
// Save files so we can decr on next checkpoint/commit:
lastFiles.addAll(segmentInfos.files(directory, false));
}
if (infoStream.isEnabled("IFD")) {
long t1 = System.nanoTime();
infoStream.message("IFD", ((t1-t0)/1000000) + " msec to checkpoint");
}
}
void incRef(SegmentInfos segmentInfos, boolean isCommit) throws IOException {
assert locked();
// If this is a commit point, also incRef the
// segments_N file:
for(final String fileName: segmentInfos.files(directory, isCommit)) {
incRef(fileName);
}
}
void incRef(Collection<String> files) {
assert locked();
for(final String file : files) {
incRef(file);
}
}
void incRef(String fileName) {
assert locked();
RefCount rc = getRefCount(fileName);
if (infoStream.isEnabled("IFD")) {
if (VERBOSE_REF_COUNTS) {
infoStream.message("IFD", " IncRef \"" + fileName + "\": pre-incr count is " + rc.count);
}
}
rc.IncRef();
}
void decRef(Collection<String> files) throws IOException {
assert locked();
for(final String file : files) {
decRef(file);
}
}
void decRef(String fileName) throws IOException {
assert locked();
RefCount rc = getRefCount(fileName);
if (infoStream.isEnabled("IFD")) {
if (VERBOSE_REF_COUNTS) {
infoStream.message("IFD", " DecRef \"" + fileName + "\": pre-decr count is " + rc.count);
}
}
if (0 == rc.DecRef()) {
// This file is no longer referenced by any past
// commit points nor by the in-memory SegmentInfos:
deleteFile(fileName);
refCounts.remove(fileName);
}
}
void decRef(SegmentInfos segmentInfos) throws IOException {
assert locked();
for (final String file : segmentInfos.files(directory, false)) {
decRef(file);
}
}
public boolean exists(String fileName) {
assert locked();
if (!refCounts.containsKey(fileName)) {
return false;
} else {
return getRefCount(fileName).count > 0;
}
}
private RefCount getRefCount(String fileName) {
assert locked();
RefCount rc;
if (!refCounts.containsKey(fileName)) {
rc = new RefCount(fileName);
refCounts.put(fileName, rc);
} else {
rc = refCounts.get(fileName);
}
return rc;
}
void deleteFiles(List<String> files) throws IOException {
assert locked();
for(final String file: files) {
deleteFile(file);
}
}
/** Deletes the specified files, but only if they are new
* (have not yet been incref'd). */
void deleteNewFiles(Collection<String> files) throws IOException {
assert locked();
for (final String fileName: files) {
// NOTE: it's very unusual yet possible for the
// refCount to be present and 0: it can happen if you
// open IW on a crashed index, and it removes a bunch
// of unref'd files, and then you add new docs / do
// merging, and it reuses that segment name.
// TestCrash.testCrashAfterReopen can hit this:
if (!refCounts.containsKey(fileName) || refCounts.get(fileName).count == 0) {
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "delete new file \"" + fileName + "\"");
}
deleteFile(fileName);
}
}
}
void deleteFile(String fileName)
throws IOException {
assert locked();
try {
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "delete \"" + fileName + "\"");
}
directory.deleteFile(fileName);
} catch (IOException e) { // if delete fails
if (directory.fileExists(fileName)) {
// Some operating systems (e.g. Windows) don't
// permit a file to be deleted while it is opened
// for read (e.g. by another process or thread). So
// we assume that when a delete fails it is because
// the file is open in another process, and queue
// the file for subsequent deletion.
if (infoStream.isEnabled("IFD")) {
infoStream.message("IFD", "unable to remove file \"" + fileName + "\": " + e.toString() + "; Will re-try later.");
}
if (deletable == null) {
deletable = new ArrayList<>();
}
deletable.add(fileName); // add to deletable
}
}
}
/**
* Tracks the reference count for a single index file:
*/
final private static class RefCount {
// fileName used only for better assert error messages
final String fileName;
boolean initDone;
RefCount(String fileName) {
this.fileName = fileName;
}
int count;
public int IncRef() {
if (!initDone) {
initDone = true;
} else {
assert count > 0: Thread.currentThread().getName() + ": RefCount is 0 pre-increment for file \"" + fileName + "\"";
}
return ++count;
}
public int DecRef() {
assert count > 0: Thread.currentThread().getName() + ": RefCount is 0 pre-decrement for file \"" + fileName + "\"";
return --count;
}
}
/**
* Holds details for each commit point. This class is
* also passed to the deletion policy. Note: this class
* has a natural ordering that is inconsistent with
* equals.
*/
final private static class CommitPoint extends IndexCommit {
Collection<String> files;
String segmentsFileName;
boolean deleted;
Directory directory;
Collection<CommitPoint> commitsToDelete;
long generation;
final Map<String,String> userData;
private final int segmentCount;
public CommitPoint(Collection<CommitPoint> commitsToDelete, Directory directory, SegmentInfos segmentInfos) throws IOException {
this.directory = directory;
this.commitsToDelete = commitsToDelete;
userData = segmentInfos.getUserData();
segmentsFileName = segmentInfos.getSegmentsFileName();
generation = segmentInfos.getGeneration();
files = Collections.unmodifiableCollection(segmentInfos.files(directory, true));
segmentCount = segmentInfos.size();
}
@Override
public String toString() {
return "IndexFileDeleter.CommitPoint(" + segmentsFileName + ")";
}
@Override
public int getSegmentCount() {
return segmentCount;
}
@Override
public String getSegmentsFileName() {
return segmentsFileName;
}
@Override
public Collection<String> getFileNames() {
return files;
}
@Override
public Directory getDirectory() {
return directory;
}
@Override
public long getGeneration() {
return generation;
}
@Override
public Map<String,String> getUserData() {
return userData;
}
/**
* Called only be the deletion policy, to remove this
* commit point from the index.
*/
@Override
public void delete() {
if (!deleted) {
deleted = true;
commitsToDelete.add(this);
}
}
@Override
public boolean isDeleted() {
return deleted;
}
}
}