com.google.gerrit.server.cache.PerThreadProjectCache Maven / Gradle / Ivy
// Copyright (C) 2023 The Android Open Source Project
//
// 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 com.google.gerrit.server.cache;
import com.google.common.collect.Maps;
import com.google.gerrit.entities.Project;
import java.util.Map;
import java.util.function.Supplier;
/**
* To prevent OOM errors on requests that would cache a lot of objects, this class enforces an
* internal limit after which no new elements are cached. All {@code computeIfAbsentWithinLimit}
* calls are served by invoking the {@code Supplier} after that.
*/
public class PerThreadProjectCache {
private static final PerThreadCache.Key PER_THREAD_PROJECT_CACHE_KEY =
PerThreadCache.Key.create(PerThreadProjectCache.class);
/**
* Cache at maximum 25 values per thread. This value was chosen arbitrarily. Some endpoints (like
* ListProjects) break the assumption that the data cached in a request is limited. To prevent
* this class from accumulating an unbound number of objects, we enforce this limit.
*/
private static final int PER_THREAD_PROJECT_CACHE_SIZE = 25;
private final Map, Object> valueByNameKey =
Maps.newHashMapWithExpectedSize(PER_THREAD_PROJECT_CACHE_SIZE);
private PerThreadProjectCache() {}
public static T getOrCompute(PerThreadCache.Key key, Supplier loader) {
PerThreadCache perThreadCache = PerThreadCache.get();
if (perThreadCache != null) {
PerThreadProjectCache perThreadProjectCache =
perThreadCache.get(PER_THREAD_PROJECT_CACHE_KEY, PerThreadProjectCache::new);
return perThreadProjectCache.computeIfAbsentWithinLimit(key, loader);
}
return loader.get();
}
protected T computeIfAbsentWithinLimit(
PerThreadCache.Key key, Supplier loader) {
@SuppressWarnings("unchecked")
T value = (T) valueByNameKey.get(key);
if (value == null) {
value = loader.get();
if (valueByNameKey.size() < PER_THREAD_PROJECT_CACHE_SIZE) {
valueByNameKey.put(key, value);
}
}
return value;
}
}