AHeise 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_r405008659
########## File path: flink-runtime/src/main/java/org/apache/flink/runtime/checkpoint/channel/ChannelStateWriterImpl.java ########## @@ -0,0 +1,186 @@ +/* + * 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.Internal; +import org.apache.flink.runtime.checkpoint.CheckpointOptions; +import org.apache.flink.runtime.io.network.buffer.Buffer; +import org.apache.flink.runtime.state.CheckpointStorageWorkerView; +import org.apache.flink.runtime.state.CheckpointStreamFactory; +import org.apache.flink.util.Preconditions; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.concurrent.ThreadSafe; + +import java.io.IOException; +import java.util.concurrent.ConcurrentHashMap; +import java.util.concurrent.ConcurrentMap; + +import static org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequest.completeInput; +import static org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequest.completeOutput; +import static org.apache.flink.runtime.checkpoint.channel.ChannelStateWriteRequest.write; + +/** + * {@link ChannelStateWriter} implemented using + * {@link CheckpointStreamFactory.CheckpointStateOutputStream CheckpointStateOutputStreams}. Internally, it has by default + * <ul> + * <li>one stream per checkpoint; having multiple streams would mean more files written and more connections opened + * (and more latency on restore)</li> + * <li>one thread; having multiple threads means more connections, couples with the implementation and increases complexity</li> + * </ul> + * Thread-safety: this class is thread-safe when used with a thread-safe {@link ChannelStateWriteRequestExecutor executor} + * (e.g. default {@link ChannelStateWriteRequestExecutorImpl}. + */ +@Internal +@ThreadSafe +public class ChannelStateWriterImpl implements ChannelStateWriter { + + private static final Logger LOG = LoggerFactory.getLogger(ChannelStateWriterImpl.class); + private static final int DEFAULT_MAX_CHECKPOINTS = 5; // currently, only single in-flight checkpoint is supported + + private final ChannelStateWriteRequestExecutor executor; + private final ConcurrentMap<Long, ChannelStateWriteResult> results; + private final int maxCheckpoints; + + /** + * Creates a {@link ChannelStateWriterImpl} with {@link #DEFAULT_MAX_CHECKPOINTS} as {@link #maxCheckpoints}. + */ + public ChannelStateWriterImpl(CheckpointStorageWorkerView streamFactoryResolver) { + this(streamFactoryResolver, DEFAULT_MAX_CHECKPOINTS); + } + + /** + * Creates a {@link ChannelStateWriterImpl} with {@link ChannelStateSerializerImpl default} {@link ChannelStateSerializer}, + * and a {@link ChannelStateWriteRequestExecutorImpl}. + * + * @param maxCheckpoints maximum number of checkpoints to be written currently or finished but not taken yet. + * @param streamFactoryResolver a factory to obtain output stream factory for a given checkpoint + */ + ChannelStateWriterImpl(CheckpointStorageWorkerView streamFactoryResolver, int maxCheckpoints) { + this( + new ConcurrentHashMap<>(maxCheckpoints), + new ChannelStateWriteRequestExecutorImpl(new ChannelStateWriteRequestDispatcherImpl(streamFactoryResolver, new ChannelStateSerializerImpl())), + maxCheckpoints + ); + } + + ChannelStateWriterImpl(ConcurrentMap<Long, ChannelStateWriteResult> results, ChannelStateWriteRequestExecutor executor, int maxCheckpoints) { + this.results = results; + this.maxCheckpoints = maxCheckpoints; + this.executor = executor; + } + + @Override + public void start(long checkpointId, CheckpointOptions checkpointOptions) { + LOG.debug("start checkpoint {} ({})", checkpointId, checkpointOptions); + ChannelStateWriteResult result = new ChannelStateWriteResult(); + ChannelStateWriteResult put = results.computeIfAbsent(checkpointId, id -> { + Preconditions.checkState(results.size() < maxCheckpoints, "results.size() > maxCheckpoints", results.size(), maxCheckpoints); + enqueue(new CheckpointStartRequest(checkpointId, result, checkpointOptions.getTargetLocation()), false); + return result; + }); + Preconditions.checkArgument(put == result, "result future already present for checkpoint id: " + checkpointId); + } + + @Override + public void addInputData(long checkpointId, InputChannelInfo info, int startSeqNum, Buffer... data) { + LOG.debug("add input data, checkpoint id: {}, channel: {}, startSeqNum: {}, num buffers: {}", + checkpointId, info, startSeqNum, data == null ? 0 : data.length); + enqueue(write(checkpointId, info, checkBufferType(data)), false); + } + + @Override + public void addOutputData(long checkpointId, ResultSubpartitionInfo info, int startSeqNum, Buffer... data) { + LOG.debug("add output data, checkpoint id: {}, channel: {}, startSeqNum: {}, num buffers: {}", + checkpointId, info, startSeqNum, data == null ? 0 : data.length); + enqueue(write(checkpointId, info, checkBufferType(data)), false); + } + + @Override + public void finishInput(long checkpointId) { + LOG.debug("finish input data, checkpoint id: {}", checkpointId); + enqueue(completeInput(checkpointId), false); + } + + @Override + public void finishOutput(long checkpointId) { + LOG.debug("finish output data, checkpoint id: {}", checkpointId); + enqueue(completeOutput(checkpointId), false); + } + + @Override + public void abort(long checkpointId, Throwable cause) { + LOG.debug("abort, checkpoint id: {}", checkpointId); + enqueue(ChannelStateWriteRequest.abort(checkpointId, cause), true); // abort already started + enqueue(ChannelStateWriteRequest.abort(checkpointId, cause), false); // abort enqueued but not started + } + + @Override + public ChannelStateWriteResult getWriteResult(long checkpointId) { + LOG.debug("requested write result, checkpoint id: {}", checkpointId); + ChannelStateWriteResult result = results.remove(checkpointId); + Preconditions.checkArgument(result != null, "channel state write result not found for checkpoint id " + checkpointId); + return result; + } + + public void open() { + executor.start(); + } + + @Override + public void close() throws IOException { + results.clear(); + executor.close(); + } + + private void enqueue(ChannelStateWriteRequest request, boolean atTheFront) { + // state check and previous errors check are performed inside the worker + try { + if (atTheFront) { + executor.submitPriority(request); + } else { + executor.submit(request); + } + } catch (Exception e) { + request.cancel(e); + throw new RuntimeException("unable to send request to worker", e); + } + } + + private static Buffer[] checkBufferType(Buffer... data) { + if (data == null) { + return new Buffer[0]; + } + try { + for (Buffer buffer : data) { + Preconditions.checkArgument(buffer.isBuffer()); Review comment: Since we encountered a hard error in Flink, there is no way to proceed and I'd probably also switch `checkArgument` to `checkState`. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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