pjfanning commented on code in PR #1494: URL: https://github.com/apache/pekko-connectors/pull/1494#discussion_r2959066207
########## google-cloud-pub-sub-grpc/src/main/scala/org/apache/pekko/stream/connectors/googlecloud/pubsub/grpc/FlowControl.scala: ########## @@ -0,0 +1,78 @@ +/* + * 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.pekko.stream.connectors.googlecloud.pubsub.grpc + +import org.apache.pekko.annotation.ApiMayChange + +import java.util.concurrent.atomic.AtomicLong + +/** + * Tracks the number of outstanding (unacknowledged) messages and provides + * a mechanism for the downstream acknowledge/nack stages to signal that + * messages have been processed, allowing the upstream gate to resume pulling. + * + * Create an instance and pass it to both `flowControlGate` (which applies + * backpressure) and `acknowledge`/`nack` overloads (which release permits). + * + * Usage: + * {{{ + * val fc = FlowControl(maxOutstandingMessages = 1000) + * + * GooglePubSub.subscribe(request, 1.second) + * .via(GooglePubSub.flowControlGate(fc)) + * .mapAsync(4)(processMessage) + * .map(msg => AcknowledgeRequest(sub, Seq(msg.ackId))) + * .to(GooglePubSub.acknowledge(parallelism = 1, fc)) + * }}} + * + * @param maxOutstandingMessages maximum number of messages allowed in-flight + * @since 2.0.0 + */ +@ApiMayChange +final class FlowControl(val maxOutstandingMessages: Long) { + require(maxOutstandingMessages > 0, "maxOutstandingMessages must be > 0") + + private[grpc] val outstanding = new AtomicLong(0) + + @volatile private[grpc] var onRelease: () => Unit = () => () + + /** Current number of outstanding (unacknowledged) messages. */ + def outstandingCount: Long = outstanding.get() + + /** Release `count` permits, signalling that messages have been acknowledged. */ + private[grpc] def release(count: Int): Unit = { + outstanding.addAndGet(-count) + onRelease() + } + + /** Acquire one permit. Returns true if under the limit. */ + private[grpc] def acquire(): Boolean = + outstanding.incrementAndGet() <= maxOutstandingMessages +} + +@ApiMayChange +object FlowControl { + + /** Create a new [[FlowControl]] instance. */ + def apply(maxOutstandingMessages: Long): FlowControl = + new FlowControl(maxOutstandingMessages) + + /** Java API: Create a new [[FlowControl]] instance. */ + def create(maxOutstandingMessages: Long): FlowControl = + new FlowControl(maxOutstandingMessages) +} Review Comment: No file should end with this symbol. The Red Circle with a line through it. Can you add an EOL at the end of all text files? -- 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] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
