m-trieu commented on code in PR #27593: URL: https://github.com/apache/beam/pull/27593#discussion_r1274302561
########## runners/google-cloud-dataflow-java/worker/src/main/java/org/apache/beam/runners/dataflow/worker/windmill/WindmillStreamPool.java: ########## @@ -0,0 +1,178 @@ +/* + * 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.runners.dataflow.worker.windmill; + +import java.util.ArrayList; +import java.util.List; +import java.util.Map; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ThreadLocalRandom; +import java.util.function.Supplier; +import javax.annotation.concurrent.ThreadSafe; +import org.apache.beam.vendor.guava.v26_0_jre.com.google.common.annotations.VisibleForTesting; +import org.joda.time.Duration; +import org.joda.time.Instant; + +/** + * Pool of homogeneous streams to Windmill. + * + * <p>The pool holds a fixed total number of streams, and keeps each stream open for a specified + * time to allow for better load-balancing. + */ +@ThreadSafe +public class WindmillStreamPool<StreamT extends WindmillServerStub.WindmillStream> { + + private final Duration streamTimeout; + private final Supplier<StreamT> streamSupplier; + private final List<WindmillStreamPool.StreamData<StreamT>> streams; + private final Map<StreamT, StreamData<StreamT>> holds; + + private WindmillStreamPool( + Duration streamTimeout, + Supplier<StreamT> streamSupplier, + List<WindmillStreamPool.StreamData<StreamT>> streams, + ConcurrentHashMap<StreamT, StreamData<StreamT>> holds) { + this.streams = streams; + this.streamTimeout = streamTimeout; + this.streamSupplier = streamSupplier; + this.holds = holds; + } + + public static <StreamT extends WindmillServerStub.WindmillStream> + WindmillStreamPool<StreamT> create( + int numStreams, Duration streamTimeout, Supplier<StreamT> streamSupplier) { + return new WindmillStreamPool<>( + streamTimeout, streamSupplier, emptyStreamList(numStreams), new ConcurrentHashMap<>()); + } + + /** + * Return a list of the given capacity populated with null. This list is used to load balance + * {@link WindmillStreamPool#getStream()} requests. It never grows in size and must be filled to + * capacity since the random used to grab a random stream is bound by the size of the list. + */ + @SuppressWarnings("nullness") + private static <StreamT extends WindmillServerStub.WindmillStream> + List<WindmillStreamPool.StreamData<StreamT>> emptyStreamList(int capacity) { + List<WindmillStreamPool.StreamData<StreamT>> streams = new ArrayList<>(capacity); + for (int i = 0; i < capacity; i++) { + streams.add(null); + } + + return streams; + } + + @VisibleForTesting + static <StreamT extends WindmillServerStub.WindmillStream> WindmillStreamPool<StreamT> forTesting( + Duration streamTimeout, + Supplier<StreamT> streamSupplier, + List<WindmillStreamPool.StreamData<StreamT>> streams, + ConcurrentHashMap<StreamT, StreamData<StreamT>> holds) { + return new WindmillStreamPool<>(streamTimeout, streamSupplier, streams, holds); + } + + /** + * Returns a stream for use that may be cached from a previous call. Each call of getStream must + * be matched with a call of releaseStream. If the stream has been cached but has timed out and no + * longer has any holds, the stream will be closed. + * + * @implNote Streams are stored in an indexed list where the index is the key to fetch the stream. + * This is so that we can "randomly" fetch a stream for better load balancing. + */ + public StreamT getStream() { + int index = ThreadLocalRandom.current().nextInt(streams.size()); Review Comment: done. -- 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]
