zentol commented on code in PR #20757: URL: https://github.com/apache/flink/pull/20757#discussion_r980973383
########## flink-core/src/main/java/org/apache/flink/api/connector/source/lib/util/GatedRateLimiter.java: ########## @@ -0,0 +1,64 @@ +/* + * 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.flink.api.connector.source.lib.util; + +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.CompletionStage; + +/** + * An implementation of {@link RateLimiter} that completes defined number of futures in-between the + * external notification events. The first cycle completes immediately, without waiting for the + * external notifications. + */ +public class GatedRateLimiter implements RateLimiter { + + private final int capacityPerCycle; + private int capacityLeft; + + /** + * Instantiates a new GatedRateLimiter. + * + * @param capacityPerCycle The number of completed futures per cycle. + */ + public GatedRateLimiter(int capacityPerCycle) { + this.capacityPerCycle = capacityPerCycle; + this.capacityLeft = capacityPerCycle + 1; + } + + CompletableFuture<Void> gatingFuture; + + @Override + public CompletionStage<Void> acquire() { + if (capacityLeft-- > 0) { + return CompletableFuture.completedFuture(null); + } else { + if (gatingFuture == null) { + gatingFuture = new CompletableFuture<>(); + } + return gatingFuture; + } + } + + @Override + public void notifyCheckpointComplete(long checkpointId) { + capacityLeft = capacityPerCycle - 1; Review Comment: I think it's a problem that the first cycle is somehow treated differently than the others; conceptually it should be _possible_ to just call notifyCheckpointComplete immediately (e.g., in the constructor) without it affecting the behavior. As I understood the reason we need this distinction is that we decrement the count _before_ the future completes, causing us to smuggle some decrements over into the next cycle. I'm currently experimenting to avoid that problem (and others incidentally): ``` public GatedRateLimiter(int capacityPerCycle) { this.capacityPerCycle = capacityPerCycle; this.capacityLeft = capacityPerCycle; } transient CompletableFuture<Void> gatingFuture = null; @Override public CompletionStage<Void> acquire() { if (gatingFuture == null) { gatingFuture = CompletableFuture.completedFuture(null); } if (capacityLeft <= 0) { gatingFuture = new CompletableFuture<>(); } return gatingFuture.thenRun(() -> capacityLeft -= 1); } @Override public void notifyCheckpointComplete(long checkpointId) { capacityLeft = capacityPerCycle; gatingFuture.complete(null); } ``` -- 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: issues-unsubscr...@flink.apache.org For queries about this service, please contact Infrastructure at: us...@infra.apache.org
