ahmedabu98 commented on code in PR #38264: URL: https://github.com/apache/beam/pull/38264#discussion_r3156441559
########## sdks/java/io/google-cloud-platform/src/main/java/org/apache/beam/sdk/io/gcp/bigquery/AppendClientCache.java: ########## @@ -0,0 +1,140 @@ +/* + * 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.beam.sdk.io.gcp.bigquery; + +import java.util.concurrent.Callable; +import java.util.concurrent.ExecutorService; +import java.util.concurrent.Executors; +import java.util.concurrent.TimeUnit; +import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.cache.Cache; +import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.cache.CacheBuilder; +import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.cache.RemovalNotification; +import org.checkerframework.checker.nullness.qual.NonNull; +import org.checkerframework.checker.nullness.qual.Nullable; +import org.joda.time.Duration; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * Encapsulates the cache of {@link AppendClientInfo} objects and the synchronization protocol + * required to use them safely. The Guava cache object is thread-safe. However our protocol requires + * that client pin the StreamAppendClient after looking up the cache, and we must ensure that the + * cache is not accessed in between the lookup and the pin (any access of the cache could trigger + * element expiration). + */ +class AppendClientCache<KeyT extends @NonNull Object> { + private static final Logger LOG = LoggerFactory.getLogger(AppendClientCache.class); + private final ExecutorService closeWriterExecutor = Executors.newCachedThreadPool(); + + private final Cache<KeyT, AppendClientInfo> appendCache; + + @SuppressWarnings({"FutureReturnValueIgnored"}) + AppendClientCache(Duration expireAfterAccess) { + this.appendCache = + CacheBuilder.newBuilder() + .expireAfterAccess(expireAfterAccess.getMillis(), TimeUnit.MILLISECONDS) + .removalListener( + (RemovalNotification<KeyT, AppendClientInfo> removal) -> { + LOG.info("Expiring append client for {}", removal.getKey()); + final @Nullable AppendClientInfo appendClientInfo = removal.getValue(); + if (appendClientInfo != null) { + // Remove the pin owned by the cache itself. Since the client has not been + // marked as closed, we + // can call unpin in this thread without worrying about blocking the thread. + appendClientInfo.unpinAppendClient(null); + // Close the client in another thread to avoid blocking the main thread. + closeWriterExecutor.submit(appendClientInfo::close); + } + }) + .build(); + } + + // The cache itself always own one pin on the object. This Callable is always used to ensure that + // the cache + // adds a pin before loading a value. + private static Callable<AppendClientInfo> wrapWithPin(Callable<AppendClientInfo> loader) { + return () -> { + AppendClientInfo client = loader.call(); + client.pinAppendClient(); + return client; + }; + } + + /** + * Atomically get an append client from the cache and add a pin. This pin is owned by the client, + * which has the responsibility of removing it. If the client is not in the cache, loader will be + * used to load the client; in this case an additional pin will be added owned by the cache, + * removed when the item is evicted. + */ + public AppendClientInfo getAndPin(KeyT key, Callable<AppendClientInfo> loader) throws Exception { + synchronized (this) { + AppendClientInfo info = appendCache.get(key, wrapWithPin(loader)); + info.pinAppendClient(); + return info; + } + } + + public AppendClientInfo putAndPin(KeyT key, Callable<AppendClientInfo> loader) throws Exception { + synchronized (this) { + AppendClientInfo info = wrapWithPin(loader).call(); Review Comment: Sorry I think I just got mixed up on the unpinning logic. I thought we were leaking resources by not unpinning the consuming `processElement`s, but I just did another pass and it looks fine to me. -- 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]
