openinx commented on a change in pull request #1793: URL: https://github.com/apache/iceberg/pull/1793#discussion_r556252305
########## File path: flink/src/main/java/org/apache/iceberg/flink/source/StreamingReaderOperator.java ########## @@ -0,0 +1,233 @@ +/* + * 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.iceberg.flink.source; + +import java.io.IOException; +import java.util.Queue; +import org.apache.flink.api.common.state.ListState; +import org.apache.flink.api.common.state.ListStateDescriptor; +import org.apache.flink.runtime.state.JavaSerializer; +import org.apache.flink.runtime.state.StateInitializationContext; +import org.apache.flink.runtime.state.StateSnapshotContext; +import org.apache.flink.streaming.api.functions.source.SourceFunction; +import org.apache.flink.streaming.api.operators.AbstractStreamOperator; +import org.apache.flink.streaming.api.operators.AbstractStreamOperatorFactory; +import org.apache.flink.streaming.api.operators.MailboxExecutor; +import org.apache.flink.streaming.api.operators.OneInputStreamOperator; +import org.apache.flink.streaming.api.operators.OneInputStreamOperatorFactory; +import org.apache.flink.streaming.api.operators.StreamOperator; +import org.apache.flink.streaming.api.operators.StreamOperatorParameters; +import org.apache.flink.streaming.api.operators.StreamSourceContexts; +import org.apache.flink.streaming.api.operators.YieldingOperatorFactory; +import org.apache.flink.streaming.api.watermark.Watermark; +import org.apache.flink.streaming.runtime.streamrecord.StreamRecord; +import org.apache.flink.streaming.runtime.tasks.ProcessingTimeService; +import org.apache.flink.table.data.RowData; +import org.apache.iceberg.relocated.com.google.common.base.Preconditions; +import org.apache.iceberg.relocated.com.google.common.collect.Lists; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * The operator that reads the {@link FlinkInputSplit splits} received from the preceding {@link + * StreamingMonitorFunction}. Contrary to the {@link StreamingMonitorFunction} which has a parallelism of 1, + * this operator can have multiple parallelism. + * + * <p>As soon as a split descriptor is received, it is put in a queue, and use {@link MailboxExecutor} + * read the actual data of the split. This architecture allows the separation of the reading thread from the one split + * processing the checkpoint barriers, thus removing any potential back-pressure. + */ +public class StreamingReaderOperator extends AbstractStreamOperator<RowData> + implements OneInputStreamOperator<FlinkInputSplit, RowData> { + + private static final Logger LOG = LoggerFactory.getLogger(StreamingReaderOperator.class); + + private final MailboxExecutor executor; + private FlinkInputFormat format; + + private transient SourceFunction.SourceContext<RowData> sourceContext; + + private transient ListState<FlinkInputSplit> inputSplitsState; + private transient Queue<FlinkInputSplit> splits; + + // This state is used to control that only one split is occupying the executor for record reading. If there're more + // splits coming, we will buffer them in flink's state. Once the executor is idle (the currentSplitState will be + // marked as IDLE), it will schedule one new split from buffered splits in flink's state to executor (the + // currentSplitState will be marked as RUNNING). After finished all records processing, the currentSplitState will + // be marked as IDLE again. + // NOTICE: all the reader and writer of this variable are the same thread, so we don't need extra synchronization. + private transient SplitState currentSplitState; Review comment: There's only one thread (the thread that running `StreamTask` ) to access this `currentSplitState`, so we don't have to make it to be `volatile`. Hope I explained the mechanism clearly in above comment, if it's still no clear, Pls bring it up , I'd like to provide more background :-) ---------------------------------------------------------------- This is an automated message from the Apache Git Service. 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