zhijiangW commented on a change in pull request #11515: [FLINK-16744][task] implement channel state persistence for unaligned checkpoints URL: https://github.com/apache/flink/pull/11515#discussion_r405262725
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/channel/ChannelStateWriteRequestExecutorImpl.java ########## @@ -0,0 +1,161 @@ +/* + * 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.runtime.checkpoint.channel; + +import org.apache.flink.annotation.VisibleForTesting; +import org.apache.flink.util.ExceptionUtils; +import org.apache.flink.util.function.RunnableWithException; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.concurrent.ThreadSafe; + +import java.io.IOException; +import java.util.ArrayList; +import java.util.List; +import java.util.concurrent.BlockingDeque; +import java.util.concurrent.CancellationException; +import java.util.concurrent.LinkedBlockingDeque; + +/** + * Executes {@link ChannelStateWriteRequest}s in a separate thread. Any exception occurred during execution causes this + * thread to stop and the exception to be re-thrown on any subsequent call. + */ +@ThreadSafe +class ChannelStateWriteRequestExecutorImpl implements ChannelStateWriteRequestExecutor { + + private static final Logger LOG = LoggerFactory.getLogger(ChannelStateWriteRequestExecutorImpl.class); + private static final int DEFAULT_HANDOVER_CAPACITY = 10_000; + + private final ChannelStateWriteRequestDispatcher dispatcher; + private final BlockingDeque<ChannelStateWriteRequest> deque; + private final Thread thread; + private volatile Exception thrown = null; + private volatile boolean wasClosed = false; + + ChannelStateWriteRequestExecutorImpl(ChannelStateWriteRequestDispatcher dispatcher) { + this(dispatcher, new LinkedBlockingDeque<>(DEFAULT_HANDOVER_CAPACITY)); + } + + ChannelStateWriteRequestExecutorImpl(ChannelStateWriteRequestDispatcher dispatcher, BlockingDeque<ChannelStateWriteRequest> deque) { + this.dispatcher = dispatcher; + this.deque = deque; + this.thread = new Thread(this::run); + this.thread.setDaemon(true); + } + + @VisibleForTesting + void run() { + try { + loop(); + } catch (Exception ex) { + thrown = ex; + } finally { + cleanupRequests(); + dispatcher.close(thrown == null ? new CancellationException() : thrown); + } + LOG.debug("loop terminated"); + } + + private void loop() throws Exception { + while (isActive()) { + try { + dispatcher.dispatch(deque.take()); + } catch (InterruptedException e) { + if (isActive()) { + LOG.debug("interrupted while waiting for a request (continue waiting)", e); + } else { + Thread.currentThread().interrupt(); + } + } + } + } + + private void cleanupRequests() { + Throwable cause = thrown == null ? new CancellationException() : thrown; + List<ChannelStateWriteRequest> drained = new ArrayList<>(); + deque.drainTo(drained); + LOG.info("discarding {} drained requests", drained.size()); + for (ChannelStateWriteRequest request : drained) { + request.cancel(cause); + } + } + + @Override + public void start() throws IllegalStateException { + this.thread.start(); + } + + @Override + public void submit(ChannelStateWriteRequest request) throws Exception { + submitInternal(request, () -> deque.add(request)); + } + + @Override + public void submitPriority(ChannelStateWriteRequest request) throws Exception { + submitInternal(request, () -> deque.addFirst(request)); + } + + private void submitInternal(ChannelStateWriteRequest request, RunnableWithException action) throws Exception { + try { + action.run(); + } catch (Exception ex) { + request.cancel(ex); + throw ex; + } + ensureRunning(); + } + + private void ensureRunning() throws Exception { + // this check should be performed *at least after* enqueuing a request + // checking before is not enough because (check + enqueue) is not atomic + if (!isActive()) { + cleanupRequests(); + throw ExceptionUtils.firstOrSuppressed(new IllegalStateException("not running"), thrown); + } + } + + private boolean isActive() { + return !wasClosed && thread.isAlive(); + } + + @Override + public void close() throws IOException { + wasClosed = true; + while (thread.isAlive()) { + thread.interrupt(); + try { + thread.join(); + } catch (InterruptedException e) { + if (!thread.isAlive()) { Review comment: If the thread is still alive, do we also need to `Thread.currentThread().interrupt()`? ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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