rkhachatryan commented on a change in pull request #10151: [FLINK-14231] Handle the processing-time timers when closing operators to make endInput semantics on the operator chain strict URL: https://github.com/apache/flink/pull/10151#discussion_r355541063
########## File path: flink-streaming-java/src/main/java/org/apache/flink/streaming/runtime/tasks/StreamOperatorWrapper.java ########## @@ -0,0 +1,253 @@ +/* + * 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.runtime.tasks; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.annotation.VisibleForTesting; +import org.apache.flink.streaming.api.operators.BoundedMultiInput; +import org.apache.flink.streaming.api.operators.BoundedOneInput; +import org.apache.flink.streaming.api.operators.MailboxExecutor; +import org.apache.flink.streaming.api.operators.StreamOperator; + +import javax.annotation.Nullable; + +import java.util.Iterator; +import java.util.NoSuchElementException; +import java.util.concurrent.CompletableFuture; +import java.util.concurrent.CompletionException; +import java.util.concurrent.ExecutionException; + +import static org.apache.flink.util.Preconditions.checkNotNull; + +/** + * This class wraps a {@link StreamOperator} and handles its close, endInput and other related logic. + * It also supports automatically transmitting the close operation to all operators on the operator chain + * behind it in the topological order. + * + * <p>Before closing the wrapped operator, it quiesces its processing time service, cancels the timers + * which registered but not yet scheduled for execution, and waits for all pending (executing) timers to + * finish. + */ +@Internal +public class StreamOperatorWrapper<OUT, OP extends StreamOperator<OUT>> { + + @Nullable + private final OP wrapped; + + private final MailboxExecutor mailboxExecutor; + + private StreamOperatorWrapper<?, ?> previous; + + private StreamOperatorWrapper<?, ?> next; + + private ProcessingTimeServiceImpl processingTimeService; + + StreamOperatorWrapper(OP wrapped, MailboxExecutor mailboxExecutor) { + this.wrapped = wrapped; + this.mailboxExecutor = checkNotNull(mailboxExecutor); + } + + public void close(StreamTask<?, ?> containingTask, boolean transitive) throws Exception { + close(containingTask, transitive, false); + } + + /** + * Ends an input of the operator contained by this wrapper. + * + * @param inputId the input ID starts from 1 which indicates the first input. + */ + public void endOperatorInput(int inputId) throws Exception { + if (wrapped instanceof BoundedOneInput) { + ((BoundedOneInput) wrapped).endInput(); + } else if (wrapped instanceof BoundedMultiInput) { + ((BoundedMultiInput) wrapped).endInput(inputId); + } + } + + public OP getStreamOperator() { + return wrapped; + } + + public MailboxExecutor getMailboxExecutor() { + return mailboxExecutor; + } + + public ProcessingTimeService getProcessingTimeService() { + return processingTimeService; + } + + void setProcessingTimeService(ProcessingTimeServiceImpl processingTimeService) { + this.processingTimeService = processingTimeService; + } + + void setPrevious(StreamOperatorWrapper previous) { + this.previous = previous; + } + + void setNext(StreamOperatorWrapper next) { + this.next = next; + } + + @VisibleForTesting + void close(StreamTask<?, ?> containingTask, boolean transitive, boolean invokingEndInput) throws Exception { + if (invokingEndInput) { + // NOTE: This only do for the case where the operator is one-input operator. At present, + // any non-head operator on the operator chain is one-input operator. + synchronized (containingTask.getCheckpointLock()) { + endOperatorInput(1); + } + } + + closeGracefully(containingTask); + + // transmit the close operation to the next operator on the operator chain in the topological order + if (transitive && next != null) { + next.close(containingTask, true, true); + } + } + + private void closeGracefully(StreamTask<?, ?> containingTask) throws InterruptedException, ExecutionException { + CompletableFuture<Void> closedFuture = new CompletableFuture<>(); + + // make sure no new processing-time timers come in + quiesceProcessingTimeService(); + + // 1. executing the close operation must be deferred to the mailbox to ensure that mails already + // in the mailbox are finished before closing the operator + // 2. to ensure that there is no longer output triggered by the processing-time timers before invoke + // the "endInput" methods of downstream operators in the operator chain, we must cancel timers not + // in executing after closing the operator and wait for timers in executing to finish + // 3. when the second step is finished, send a close mail to ensure that the processing-time timers + // yet in mailbox are finished before exiting the following mailbox processing loop + // TODO: To ensure the strict semantics of "close", the operator should be allowed to decide how to + // handle (cancel or trigger) the pending timers before being closed, and the second step must be + // finished before the first step + // send an empty mail to trigger the following mailbox-processing loop to exit + CompletableFuture<Void> closingFuture = deferCloseOperatorToMailbox(containingTask) + .thenRun(this::cancelProcessingTimeTimers) + .thenRun(() -> sendClosedMail(closedFuture)); + + // run the mailbox processing loop until the closing operation is finished + while (!(closingFuture.isCompletedExceptionally() || closedFuture.isDone())) { + mailboxExecutor.yield(); + } + + // expose the exception thrown when closing the operator + if (closingFuture.isCompletedExceptionally()) { + closingFuture.get(); + } + } + + private void quiesceProcessingTimeService() { + if (processingTimeService != null) { + processingTimeService.quiesce(); + } + } + + private CompletableFuture<Void> deferCloseOperatorToMailbox(StreamTask<?, ?> containingTask) { + CompletableFuture<Void> closeOperatorFuture = new CompletableFuture<>(); + + mailboxExecutor.execute( + () -> { + try { + closeOperator(containingTask); + closeOperatorFuture.complete(null); + } catch (Throwable t) { + closeOperatorFuture.completeExceptionally(t); + } + }, + "StreamOperatorWrapper#closeOperator for " + wrapped + ); + return closeOperatorFuture; + } + + private void cancelProcessingTimeTimers() throws CompletionException { + if (processingTimeService == null) { + return; + } + + try { + processingTimeService.cancelTimersGracefullyAfterQuiesce().get(); + } catch (Throwable throwable) { + throw new CompletionException(throwable); + } + } + + private void sendClosedMail(CompletableFuture<Void> closedFuture) { + mailboxExecutor.execute( + () -> closedFuture.complete(null), "emptyMail in StreamOperatorWrapper#closeGracefully for " + wrapped); + } + + private void closeOperator(StreamTask<?, ?> containingTask) throws Exception { + synchronized (containingTask.getCheckpointLock()) { + if (wrapped != null) { + wrapped.close(); + } + } + } + + static class ReadIterator implements Iterator<StreamOperatorWrapper<?, ?>> { + + private StreamOperatorWrapper<?, ?> next; + + ReadIterator(StreamOperatorWrapper<?, ?> first) { + this.next = first; + } + + @Override + public boolean hasNext() { + return this.next != null; + } + + @Override + public StreamOperatorWrapper<?, ?> next() { + if (hasNext()) { + StreamOperatorWrapper<?, ?> current = next; + this.next = this.next.next; + return current; + } + + throw new NoSuchElementException(); + } + } + + static class ReverseReadIterator implements Iterator<StreamOperatorWrapper<?, ?>> { + + private StreamOperatorWrapper<?, ?> next; + + ReverseReadIterator(StreamOperatorWrapper<?, ?> first) { + this.next = first; + } + + @Override + public boolean hasNext() { + return this.next != null; + } + + @Override + public StreamOperatorWrapper<?, ?> next() { + if (hasNext()) { + StreamOperatorWrapper<?, ?> current = next; + this.next = this.next.previous; + return current; + } + + throw new NoSuchElementException(); + } + } Review comment: We can have just one iterator class implementing `ListIterator` interface with `next()` and `previous()` methods. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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