VladRodionov commented on code in PR #8231: URL: https://github.com/apache/hbase/pull/8231#discussion_r3238193794
########## hbase-server/src/main/java/org/apache/hadoop/hbase/io/hfile/cache/NoOpCacheAccessService.java: ########## @@ -0,0 +1,216 @@ +/* + * 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.hadoop.hbase.io.hfile.cache; + +import java.util.Objects; +import org.apache.hadoop.conf.Configuration; +import org.apache.hadoop.hbase.io.hfile.BlockCacheKey; +import org.apache.hadoop.hbase.io.hfile.CacheStats; +import org.apache.hadoop.hbase.io.hfile.Cacheable; +import org.apache.yetus.audience.InterfaceAudience; + +/** + * Disabled-cache implementation of {@link CacheAccessService}. + * <p> + * {@code NoOpCacheAccessService} is useful when block cache access is disabled but callers still + * want to depend on a non-null {@link CacheAccessService}. It never stores blocks, never returns + * cached blocks, reports zero capacity and occupancy, and treats all invalidation requests as + * no-ops. + * </p> + * <p> + * This implementation should not be used to hide configuration mistakes. It represents an explicit + * disabled-cache state and should be selected only when the caller has determined that no block + * cache is available or desired. + * </p> + */ [email protected] +public final class NoOpCacheAccessService implements CacheAccessService { + + private static final String NAME = "NoOpCacheAccessService"; + + private final CacheStats stats; + + /** + * Creates a disabled cache access service with its own {@link CacheStats} instance. + */ + public NoOpCacheAccessService() { + this(new CacheStats(NAME)); + } + + /** + * Creates a disabled cache access service with the supplied statistics object. + * <p> + * Allowing the statistics object to be supplied makes tests easier and allows callers to preserve + * existing metrics conventions if needed. + * </p> + * @param stats cache statistics object + */ + public NoOpCacheAccessService(CacheStats stats) { + this.stats = Objects.requireNonNull(stats, "stats must not be null"); + } + + /** + * Returns the service name. + * @return service name + */ + @Override + public String getName() { + return NAME; + } + + /** + * Always returns {@code null} because this service does not store blocks. + * @param cacheKey block to fetch + * @param context cache request context + * @return always {@code null} + */ + @Override + public Cacheable getBlock(BlockCacheKey cacheKey, CacheRequestContext context) { + return null; + } Review Comment: Fixed. -- 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]
