org.apache.jackrabbit.oak.segment.file.Reclaimers Maven / Gradle / Ivy
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* 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.jackrabbit.oak.segment.file;
import static com.google.common.base.Preconditions.checkNotNull;
import com.google.common.base.Predicate;
import org.apache.jackrabbit.oak.segment.compaction.SegmentGCOptions.GCType;
import org.apache.jackrabbit.oak.segment.file.tar.GCGeneration;
import org.jetbrains.annotations.NotNull;
/**
* Helper class exposing static factories for reclaimers. A reclaimer
* is a predicate used during the cleanup phase of garbage collection
* to decide whether a segment of a given generation is reclaimable.
*/
class Reclaimers {
private Reclaimers() {
// Prevent instantiation.
}
/**
* Create a reclaimer for segments of old generations. Whether a segment is considered old and
* thus reclaimable depends on the type of the most recent GC operation and the number of
* retained generations.
*
* In the case of {@link GCType#FULL FULL} a segment is reclaimable if its
* {@link GCGeneration#getFullGeneration() full generation} is at least {@code retainedGenerations}
* in the past wrt. {@code referenceGeneration} or if its
* {@link GCGeneration#getGeneration() generation} is at least {@code retainedGenerations} in the
* past wrt. {@code referenceGeneration} and it not a {@link GCGeneration#isCompacted() compacted segment}.
*
* In the case of {@link GCType#TAIL TAIL} a segment is reclaimable if its
* {@link GCGeneration#getGeneration() generation} is at least {@code retainedGenerations} in the
* past wrt. {@code referenceGeneration} and the segment is not in the same tail as
* segments of the {@code referenceGeneration}. A segment is in the same tail as another segment
* if it is a {@link GCGeneration#isCompacted() compacted segment} and both segments have
* the same {@code full generation}.
*
* @param lastGCType type of the most recent GC operation. {@link GCType#FULL} if unknown.
* @param referenceGeneration generation used as reference for determining the age of other segments.
* @param retainedGenerations number of generations to retain.
*/
static Predicate newOldReclaimer(
@NotNull GCType lastGCType,
@NotNull final GCGeneration referenceGeneration,
int retainedGenerations) {
switch (checkNotNull(lastGCType)) {
case FULL:
return newOldFullReclaimer(referenceGeneration, retainedGenerations);
case TAIL:
return newOldTailReclaimer(referenceGeneration, retainedGenerations);
default:
throw new IllegalArgumentException("Invalid gc type: " + lastGCType);
}
}
private static Predicate newOldFullReclaimer(
@NotNull final GCGeneration referenceGeneration,
int retainedGenerations) {
return new Predicate() {
@Override
public boolean apply(GCGeneration generation) {
return isOldFull(generation) || (isOld(generation) && !generation.isCompacted());
}
private boolean isOld(GCGeneration generation) {
return referenceGeneration.compareWith(generation) >= retainedGenerations;
}
private boolean isOldFull(GCGeneration generation) {
return referenceGeneration.compareFullGenerationWith(generation) >= retainedGenerations;
}
@Override
public String toString() {
return String.format(
"(full generation older than %d.%d, with %d retained generations)",
referenceGeneration.getGeneration(),
referenceGeneration.getFullGeneration(),
retainedGenerations
);
}
};
}
private static Predicate newOldTailReclaimer(
@NotNull final GCGeneration referenceGeneration,
int retainedGenerations) {
return new Predicate() {
@Override
public boolean apply(GCGeneration generation) {
return isOld(generation) && !sameCompactedTail(generation);
}
private boolean isOld(GCGeneration generation) {
return referenceGeneration.compareWith(generation) >= retainedGenerations;
}
private boolean sameCompactedTail(GCGeneration generation) {
return generation.isCompacted()
&& generation.getFullGeneration() == referenceGeneration.getFullGeneration();
}
@Override
public String toString() {
return String.format(
"(generation older than %d.%d, with %d retained generations and not in the same compacted tail)",
referenceGeneration.getGeneration(),
referenceGeneration.getFullGeneration(),
retainedGenerations
);
}
};
}
/**
* Create an exact reclaimer. An exact reclaimer reclaims only segment of on single generation.
* @param referenceGeneration the generation to collect.
* @return an new instance of an exact reclaimer for segments with their generation
* matching {@code referenceGeneration}.
*/
static Predicate newExactReclaimer(@NotNull final GCGeneration referenceGeneration) {
return new Predicate() {
@Override
public boolean apply(GCGeneration generation) {
return generation.equals(referenceGeneration);
}
@Override
public String toString() {
return "(generation==" + referenceGeneration + ")";
}
};
}
}