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MajorCompaction.java
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/
MajorCompaction.java
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/*
* Copyright 2015 the original author or authors.
*
* Licensed 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 net.kuujo.copycat.raft.log;
import net.kuujo.copycat.raft.log.entry.Entry;
import net.kuujo.copycat.raft.log.entry.EntryFilter;
import net.kuujo.copycat.util.ExecutionContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.CompletableFuture;
/**
* Major compaction.
*
* @author <a href="http://github.com/kuujo">Jordan Halterman</a>
*/
public class MajorCompaction extends Compaction {
private final Logger LOGGER = LoggerFactory.getLogger(MajorCompaction.class);
private final EntryFilter filter;
private final ExecutionContext context;
public MajorCompaction(long index, EntryFilter filter, ExecutionContext context) {
super(index);
this.filter = filter;
this.context = context;
}
@Override
public Type type() {
return Type.MAJOR;
}
@Override
CompletableFuture<Void> run(SegmentManager segments) {
CompletableFuture<Void> future = new CompletableFuture<>();
context.execute(() -> {
LOGGER.info("Compacting the log");
setRunning(true);
compactSegments(getActiveSegments(segments).iterator(), segments, future).whenComplete((result, error) -> {
setRunning(false);
});
});
return future;
}
/**
* Returns a list of active segments.
*/
private List<Segment> getActiveSegments(SegmentManager manager) {
List<Segment> segments = new ArrayList<>();
for (Segment segment : manager.segments()) {
if (!segment.isEmpty() && segment.lastIndex() <= index()) {
segments.add(segment);
}
}
LOGGER.debug("found {} compactable segments", segments.size());
return segments;
}
/**
* Compacts a list of active segments.
*/
private CompletableFuture<Void> compactSegments(Iterator<Segment> iterator, SegmentManager manager, CompletableFuture<Void> future) {
if (iterator.hasNext()) {
compactSegment(iterator.next(), manager).whenComplete((result, error) -> {
if (error == null) {
compactSegments(iterator, manager, future);
} else {
future.completeExceptionally(error);
}
});
} else {
future.complete(null);
}
return future;
}
/**
* Compacts a single active segment.
*/
private CompletableFuture<Void> compactSegment(Segment segment, SegmentManager manager) {
return shouldCompactSegment(segment, new CompletableFuture<>()).thenCompose(compact -> {
if (compact) {
LOGGER.debug("compacting {}", segment);
Segment compactSegment;
try (SegmentDescriptor descriptor = SegmentDescriptor.builder()
.withId(segment.descriptor().id())
.withVersion(segment.descriptor().version() + 1)
.withIndex(segment.descriptor().index())
.withMaxEntrySize(segment.descriptor().maxEntrySize())
.withMaxSegmentSize(segment.descriptor().maxSegmentSize())
.withMaxEntries(segment.descriptor().maxEntries())
.build()) {
compactSegment = manager.createSegment(descriptor);
}
return compactSegment(segment, segment.firstIndex(), compactSegment, new CompletableFuture<>()).thenAccept(manager::replace);
} else {
return CompletableFuture.completedFuture(null);
}
});
}
/**
* Compacts a single active segment recursively.
*/
private CompletableFuture<Segment> compactSegment(Segment segment, long index, Segment compactSegment, CompletableFuture<Segment> future) {
Entry entry = segment.getEntry(index);
if (entry != null) {
filter.accept(entry, this).whenCompleteAsync((accept, error) -> {
if (error == null) {
if (accept) {
compactSegment.appendEntry(entry);
} else {
compactSegment.skip(1);
}
if (index == segment.lastIndex()) {
future.complete(compactSegment);
} else {
compactSegment(segment, index + 1, compactSegment, future);
}
}
entry.close();
}, context);
} else {
compactSegment.skip(1);
if (index == segment.lastIndex()) {
future.complete(compactSegment);
} else {
context.execute(() -> compactSegment(segment, index + 1, compactSegment, future));
}
}
return future;
}
/**
* Determines whether a segment should be compacted.
*/
private CompletableFuture<Boolean> shouldCompactSegment(Segment segment, CompletableFuture<Boolean> future) {
LOGGER.debug("evaluating {} for major compaction", segment);
return shouldCompactSegment(segment, segment.firstIndex(), future);
}
/**
* Determines whether a segment should be compacted.
*/
private CompletableFuture<Boolean> shouldCompactSegment(Segment segment, long index, CompletableFuture<Boolean> future) {
Entry entry = segment.getEntry(index);
if (entry != null) {
filter.accept(entry, this).whenCompleteAsync((accept, error) -> {
entry.close();
if (error == null) {
if (!accept) {
future.complete(true);
} else if (index == segment.lastIndex()) {
future.complete(false);
} else {
shouldCompactSegment(segment, index + 1, future);
}
} else {
future.complete(true);
}
}, context);
} else if (index == segment.lastIndex()) {
future.complete(false);
} else {
context.execute(() -> shouldCompactSegment(segment, index + 1, future));
}
return future;
}
}