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/*
* Copyright Camunda Services GmbH and/or licensed to Camunda Services GmbH under
* one or more contributor license agreements. See the NOTICE file distributed
* with this work for additional information regarding copyright ownership.
* Licensed under the Zeebe Community License 1.1. You may not use this file
* except in compliance with the Zeebe Community License 1.1.
*/
package io.camunda.zeebe.journal.file;
import static com.google.common.base.Preconditions.checkNotNull;
import io.camunda.zeebe.journal.CorruptedJournalException;
import io.camunda.zeebe.journal.JournalException;
import io.camunda.zeebe.journal.JournalMetaStore;
import io.camunda.zeebe.util.logging.ThrottledLogger;
import java.io.File;
import java.io.IOException;
import java.nio.file.DirectoryStream;
import java.nio.file.Files;
import java.nio.file.Path;
import java.time.Duration;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Collections;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import java.util.SortedMap;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionException;
import java.util.concurrent.ConcurrentSkipListMap;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/** Create new segments. Load existing segments from the disk. Keep track of all segments. */
final class SegmentsManager implements AutoCloseable {
private static final long FIRST_SEGMENT_ID = 1;
private static final long INITIAL_INDEX = 1;
private static final long INITIAL_ASQN = SegmentedJournal.ASQN_IGNORE;
private static final Logger LOG = LoggerFactory.getLogger(SegmentsManager.class);
private static final Logger THROTTLED_LOG = new ThrottledLogger(LOG, Duration.ofSeconds(5));
private final NavigableMap segments = new ConcurrentSkipListMap<>();
private CompletableFuture nextSegment = null;
private final JournalMetrics journalMetrics;
private final JournalIndex journalIndex;
private final int maxSegmentSize;
private final File directory;
private final SegmentLoader segmentLoader;
private final String name;
private final JournalMetaStore metaStore;
private volatile Segment currentSegment;
SegmentsManager(
final JournalIndex journalIndex,
final int maxSegmentSize,
final File directory,
final String name,
final SegmentLoader segmentLoader,
final JournalMetrics journalMetrics,
final JournalMetaStore metaStore) {
this.name = checkNotNull(name, "name cannot be null");
this.journalIndex = journalIndex;
this.maxSegmentSize = maxSegmentSize;
this.directory = directory;
this.segmentLoader = segmentLoader;
this.journalMetrics = journalMetrics;
this.metaStore = metaStore;
}
@Override
public void close() {
segments
.values()
.forEach(
segment -> {
LOG.debug("Closing segment: {}", segment);
segment.close();
});
if (nextSegment != null) {
try {
nextSegment.join();
} catch (final Exception e) {
LOG.warn(
"Next segment preparation failed during close, ignoring and proceeding to close", e);
}
nextSegment = null;
}
currentSegment = null;
}
Segment getCurrentSegment() {
return currentSegment;
}
Segment getFirstSegment() {
final Map.Entry segment = segments.firstEntry();
return segment != null ? segment.getValue() : null;
}
Segment getLastSegment() {
final Map.Entry segment = segments.lastEntry();
return segment != null ? segment.getValue() : null;
}
/**
* Creates and returns the next segment.
*
* @return The next segment.
* @throws IllegalStateException if the segment manager is not open
*/
Segment getNextSegment() {
final Segment lastSegment = getLastSegment();
final var lastWrittenAsqn = lastSegment != null ? lastSegment.lastAsqn() : INITIAL_ASQN;
final var nextSegmentIndex = currentSegment.lastIndex() + 1;
final SegmentDescriptor descriptor =
SegmentDescriptor.builder()
.withId(lastSegment != null ? lastSegment.descriptor().id() + 1 : 1)
.withIndex(nextSegmentIndex)
.withMaxSegmentSize(maxSegmentSize)
.build();
if (nextSegment != null) {
try {
currentSegment =
nextSegment.join().initializeForUse(nextSegmentIndex, lastWrittenAsqn, journalMetrics);
} catch (final CompletionException e) {
LOG.error("Failed to acquire next segment, retrying synchronously now.", e);
nextSegment = null;
currentSegment = createSegment(descriptor, lastWrittenAsqn);
}
} else {
currentSegment = createSegment(descriptor, lastWrittenAsqn);
}
prepareNextSegment();
segments.put(descriptor.index(), currentSegment);
journalMetrics.incSegmentCount();
return currentSegment;
}
Segment getNextSegment(final long index) {
final Map.Entry nextSegment = segments.higherEntry(index);
return nextSegment != null ? nextSegment.getValue() : null;
}
Segment getSegment(final long index) {
// Check if the current segment contains the given index first in order to prevent an
// unnecessary map lookup.
if (currentSegment != null && index > currentSegment.index()) {
return currentSegment;
}
// If the index is in another segment, get the entry with the next lowest first index.
final Map.Entry segment = segments.floorEntry(index);
if (segment != null) {
return segment.getValue();
}
return getFirstSegment();
}
private long getFirstIndex() {
final var firstSegment = getFirstSegment();
return firstSegment != null ? firstSegment.index() : 0;
}
boolean deleteUntil(final long index) {
final Map.Entry segmentEntry = segments.floorEntry(index);
if (segmentEntry == null) {
return false;
}
final SortedMap compactSegments =
segments.headMap(segmentEntry.getValue().index());
if (compactSegments.isEmpty()) {
THROTTLED_LOG.debug(
"No segments can be deleted with index < {} (first log index: {})",
index,
getFirstIndex());
return false;
}
LOG.debug(
"{} - Deleting log up from {} up to {} (removing {} segments)",
name,
getFirstIndex(),
compactSegments.get(compactSegments.lastKey()).index(),
compactSegments.size());
for (final Segment segment : compactSegments.values()) {
LOG.trace("{} - Deleting segment: {}", name, segment);
segment.delete();
journalMetrics.decSegmentCount();
}
// removes them from the segment map
compactSegments.clear();
journalIndex.deleteUntil(index);
return true;
}
/**
* Resets and returns the first segment in the journal.
*
* @param index the starting index of the journal
* @return the first segment
*/
Segment resetSegments(final long index) {
// reset the last flushed index before deleting data to avoid data corruption on start up in
// case of node crash
// setting the last flushed index to a semantic-null value will let us know on start up that
// there is "nothing" written, even if we cannot read the descriptor (e.g. if we crash after
// creating the segment but before writing its descriptor)
metaStore.resetLastFlushedIndex();
// delete the segments in reverse order, such that if the operation is interrupted (e.g. crash)
// in the middle, there are no gaps in the log (or between the log and snapshot)
final Iterator it = segments.descendingMap().values().iterator();
while (it.hasNext()) {
// we explicitly do not want to close the segment, as we may be only soft deleting it here to
// allow readers to finish what they're doing and avoid a race condition with unmapping the
// underlying buffer
//noinspection resource
final var segment = it.next();
segment.delete();
it.remove();
journalMetrics.decSegmentCount();
}
final SegmentDescriptor descriptor =
SegmentDescriptor.builder()
.withId(1)
.withIndex(index)
.withMaxSegmentSize(maxSegmentSize)
.build();
currentSegment = createSegment(descriptor, INITIAL_ASQN);
segments.put(index, currentSegment);
journalMetrics.incSegmentCount();
return currentSegment;
}
/**
* Removes a segment.
*
* @param segment The segment to remove.
*/
void removeSegment(final Segment segment) {
//noinspection resource
segments.remove(segment.index());
journalMetrics.decSegmentCount();
segment.delete();
resetCurrentSegment();
}
/** Resets the current segment, creating a new segment if necessary. */
private void resetCurrentSegment() {
final Segment lastSegment = getLastSegment();
if (lastSegment != null) {
currentSegment = lastSegment;
} else {
final SegmentDescriptor descriptor =
SegmentDescriptor.builder()
.withId(FIRST_SEGMENT_ID)
.withIndex(INITIAL_INDEX)
.withMaxSegmentSize(maxSegmentSize)
.build();
currentSegment = createSegment(descriptor, INITIAL_ASQN);
segments.put(1L, currentSegment);
journalMetrics.incSegmentCount();
}
}
/** Loads existing segments from the disk */
void open() {
final var openDurationTimer = journalMetrics.startJournalOpenDurationTimer();
// Load existing log segments from disk.
for (final Segment segment : loadSegments()) {
segments.put(segment.descriptor().index(), segment);
journalMetrics.incSegmentCount();
}
// If a segment doesn't already exist, create an initial segment starting at index 1.
if (!segments.isEmpty()) {
currentSegment = segments.lastEntry().getValue();
} else {
final SegmentDescriptor descriptor =
SegmentDescriptor.builder()
.withId(FIRST_SEGMENT_ID)
.withIndex(INITIAL_INDEX)
.withMaxSegmentSize(maxSegmentSize)
.build();
currentSegment = createSegment(descriptor, INITIAL_ASQN);
segments.put(1L, currentSegment);
journalMetrics.incSegmentCount();
}
// observe the journal open duration
openDurationTimer.close();
// Delete files that were previously marked for deletion but did not get deleted because the
// node was stopped. It is safe to delete it now since there are no readers opened for these
// segments.
deleteDeferredFiles();
}
private void prepareNextSegment() {
final var descriptor =
SegmentDescriptor.builder()
.withId(currentSegment.id() + 1)
.withIndex(INITIAL_INDEX)
.withMaxSegmentSize(maxSegmentSize)
.build();
nextSegment = CompletableFuture.supplyAsync(() -> createUninitializedSegment(descriptor));
}
Collection getTailSegments(final long index) {
final var segment = getSegment(index);
if (segment == null) {
return Collections.emptySet();
}
return Collections.unmodifiableSortedMap(segments.tailMap(segment.index(), true)).values();
}
private UninitializedSegment createUninitializedSegment(final SegmentDescriptor descriptor) {
final var segmentFile = SegmentFile.createSegmentFile(name, directory, descriptor.id());
return segmentLoader.createUninitializedSegment(segmentFile.toPath(), descriptor, journalIndex);
}
private Segment createSegment(final SegmentDescriptor descriptor, final long lastWrittenAsqn) {
final var segmentFile = SegmentFile.createSegmentFile(name, directory, descriptor.id());
return segmentLoader.createSegment(
segmentFile.toPath(), descriptor, lastWrittenAsqn, journalIndex);
}
/**
* Loads all segments from disk.
*
* @return A collection of segments for the log.
*/
private Collection loadSegments() {
final var lastFlushedIndex = metaStore.loadLastFlushedIndex();
// Ensure log directories are created.
//noinspection ResultOfMethodCallIgnored
directory.mkdirs();
final List segments = new ArrayList<>();
final List files = getSortedLogSegments();
Segment previousSegment = null;
for (int i = 0; i < files.size(); i++) {
final File file = files.get(i);
try {
LOG.debug("Found segment file: {}", file.getName());
final Segment segment =
segmentLoader.loadExistingSegment(
file.toPath(),
previousSegment != null ? previousSegment.lastAsqn() : INITIAL_ASQN,
journalIndex);
if (i > 0) {
// throws CorruptedJournalException if there is gap
checkForIndexGaps(segments.get(i - 1), segment);
}
final boolean isLastSegment = i == files.size() - 1;
if (isLastSegment && segment.lastIndex() < lastFlushedIndex) {
throw new CorruptedJournalException(
"Expected to find records until index %d, but last index is %d"
.formatted(lastFlushedIndex, segment.lastIndex()));
}
segments.add(segment);
previousSegment = segment;
} catch (final CorruptedJournalException e) {
if (handleSegmentCorruption(files, segments, i, lastFlushedIndex)) {
return segments;
}
throw e;
}
}
return segments;
}
private void checkForIndexGaps(final Segment prevSegment, final Segment segment) {
if (prevSegment.lastIndex() != segment.index() - 1) {
throw new CorruptedJournalException(
String.format(
"Log segment %s is not aligned with previous segment %s (last index: %d).",
segment, prevSegment, prevSegment.lastIndex()));
}
}
/** Returns true if segments after corrupted segment were deleted; false, otherwise */
private boolean handleSegmentCorruption(
final List files,
final List segments,
final int failedIndex,
final long lastFlushedIndex) {
// if we've never flushed anything, then we can simply go head and delete the segment; otherwise
// fail if we've already flushed the failing index
if (metaStore.hasLastFlushedIndex()) {
long lastSegmentIndex = 0;
if (!segments.isEmpty()) {
final Segment previousSegment = segments.get(segments.size() - 1);
lastSegmentIndex = previousSegment.lastIndex();
}
if (lastFlushedIndex > lastSegmentIndex) {
return false;
}
}
deleteUnflushedSegments(files, failedIndex, lastFlushedIndex);
return true;
}
private void deleteUnflushedSegments(
final List files, final int failedIndex, final long lastFlushedIndex) {
LOG.debug(
"Found corrupted segment after last ack'ed index {}. Deleting segments {} - {}",
lastFlushedIndex,
files.get(failedIndex).getName(),
files.get(files.size() - 1).getName());
for (int i = failedIndex; i < files.size(); i++) {
final File file = files.get(i);
try {
Files.delete(file.toPath());
} catch (final IOException e) {
throw new JournalException(
String.format(
"Failed to delete log segment '%s' when handling corruption.", file.getName()),
e);
}
}
}
/** Returns an array of valid log segments sorted by their id which may be empty but not null. */
private List getSortedLogSegments() {
final File[] files =
directory.listFiles(file -> file.isFile() && SegmentFile.isSegmentFile(name, file));
if (files == null) {
throw new IllegalStateException(
String.format(
"Could not list files in directory '%s'. Either the path doesn't point to a directory or an I/O error occurred.",
directory));
}
Arrays.sort(files, Comparator.comparingInt(f -> SegmentFile.getSegmentIdFromPath(f.getName())));
return Arrays.asList(files);
}
private void deleteDeferredFiles() {
try (final DirectoryStream segmentsToDelete =
Files.newDirectoryStream(
directory.toPath(),
path -> SegmentFile.isDeletedSegmentFile(name, path.getFileName().toString()))) {
segmentsToDelete.forEach(this::deleteDeferredFile);
} catch (final IOException e) {
LOG.warn(
"Could not delete segment files marked for deletion in {}. This can result in unnecessary disk usage.",
directory.toPath(),
e);
}
}
private void deleteDeferredFile(final Path segmentFileToDelete) {
try {
Files.deleteIfExists(segmentFileToDelete);
} catch (final IOException e) {
LOG.warn(
"Could not delete file {} which is marked for deletion. This can result in unnecessary disk usage.",
segmentFileToDelete,
e);
}
}
}
