pnowojski commented on code in PR #24895: URL: https://github.com/apache/flink/pull/24895#discussion_r1631423299
########## flink-streaming-java/src/main/java/org/apache/flink/streaming/api/operators/MailboxWatermarkProcessor.java: ########## @@ -0,0 +1,92 @@ +/* + * 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.streaming.api.operators; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.api.common.operators.MailboxExecutor; +import org.apache.flink.streaming.api.watermark.Watermark; +import org.apache.flink.streaming.runtime.streamrecord.StreamRecord; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * A helper class to let operators emit watermarks incrementally from mailbox. Instead of emitting + * all the watermarks at once in a single {@code processWatermark} call, if a mail in mailbox is + * present, the process of firing timers is interrupted and a continuation to finish it off later is + * scheduled via a mailbox mail. + * + * <p>Note that interrupting firing timers can change order of some invocations. It is possible that + * between firing timers, some records might be processed. + */ +@Internal +public class MailboxWatermarkProcessor<OUT> { + protected static final Logger LOG = LoggerFactory.getLogger(MailboxWatermarkProcessor.class); + + private final Output<StreamRecord<OUT>> output; + private final MailboxExecutor mailboxExecutor; + private final InternalTimeServiceManager<?> internalTimeServiceManager; + /** + * Flag to indicate whether a progress watermark is scheduled in the mailbox. This is used to + * avoid duplicate scheduling in case we have multiple watermarks to process. + */ + private boolean progressWatermarkScheduled = false; + + private Watermark maxInputWatermark = Watermark.UNINITIALIZED; + + public MailboxWatermarkProcessor( + Output<StreamRecord<OUT>> output, + MailboxExecutor mailboxExecutor, + InternalTimeServiceManager<?> internalTimeServiceManager) { + this.output = checkNotNull(output); + this.mailboxExecutor = checkNotNull(mailboxExecutor); + this.internalTimeServiceManager = checkNotNull(internalTimeServiceManager); + } + + public void emitWatermarkInsideMailbox(Watermark mark) throws Exception { + maxInputWatermark = + new Watermark(Math.max(maxInputWatermark.getTimestamp(), mark.getTimestamp())); Review Comment: Not swallow, but supersede. I don't see how it should cause any problems, because ultimately all timers will be fired in the same order regardless. We also have never made any guarantees that `#processWatermark(x)` will be called for any specific values `x`. Also note, watermarks can be superseded in other places as well. For example watermark valves/gates/multiplexers can behave in the same way as well. If there some hiccup, watermarks smaller watermarks can be aggregated into larger one. -- 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]
