szetszwo commented on code in PR #1239: URL: https://github.com/apache/ratis/pull/1239#discussion_r2001805183
########## ratis-server-api/src/main/java/org/apache/ratis/server/protocol/TermIndexImpl.java: ########## @@ -0,0 +1,144 @@ +/* + * 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.ratis.server.protocol; + +import org.apache.ratis.thirdparty.com.google.common.collect.MapMaker; + +import java.util.Map; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; +import java.util.concurrent.atomic.AtomicInteger; +import java.util.function.Consumer; + +/** + * An implementation of {@link TermIndex}. + * Note that this is not a public API. + */ +class TermIndexImpl implements TermIndex { + private static final AtomicInteger OBJECT_COUNT = new AtomicInteger(); + + /** Weak value cache -- the same {@link TermIndex} will not be created more than once. */ + static final class Cache { + private Cache() {} + + private static <K, V> ConcurrentMap<K, V> newMap() { + return new MapMaker().weakValues().makeMap(); + } + + /** Map: term -> (index -> {@link TermIndex}). */ + private static final ConcurrentMap<Long, ConcurrentMap<Long, TermIndexImpl>> MAP = new ConcurrentHashMap<>(); + + private static TermIndex getOrCreate(long term, long index) { + final ConcurrentMap<Long, TermIndexImpl> indexMap = MAP.computeIfAbsent(term, k -> newMap()); + final TermIndex computed = indexMap.computeIfAbsent(index, i -> new TermIndexImpl(term, i)); + if ((OBJECT_COUNT.get() & 0xFFFF) == 0) { + cleanupEmptyInnerMaps(); // cleanup empty maps once in a while + } + return computed; + } + + static int indexCount(long term) { + final ConcurrentMap<Long, TermIndexImpl> indexMap = MAP.get(term); + if (indexMap == null) { + return 0; + } + + // size() may return incorrect result; see Guava MapMaker javadoc + int n = 0; + for (Long ignored : indexMap.keySet()) { + n++; + } + return n; + } + + static void cleanupEmptyInnerMaps() { + // isEmpty() may return incorrect result; see Guava MapMaker javadoc + MAP.values().removeIf(e -> !e.entrySet().iterator().hasNext()); + } + + static int dump(Consumer<Object> out) { + out.accept("TermIndex Cache:\n"); + int emptyCount = 0; + for (Map.Entry<Long, ConcurrentMap<Long, TermIndexImpl>> entry : MAP.entrySet()) { + final long term = entry.getKey(); + final ConcurrentMap<Long, TermIndexImpl> indexMap = entry.getValue(); + final int count = indexCount(term); + if (count == 0) { + emptyCount++; + } + + out.accept(" term=" + term); + out.accept(indexMap.keySet()); + out.accept(" count=" + indexCount(term)); Review Comment: You are right, we should reuse `count`. -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
