SreeramGarlapati commented on a change in pull request #2660: URL: https://github.com/apache/iceberg/pull/2660#discussion_r652401702
########## File path: spark3/src/main/java/org/apache/iceberg/spark/source/SparkMicroBatchStream.java ########## @@ -0,0 +1,310 @@ +/* + * 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.spark.source; + +import java.io.BufferedWriter; +import java.io.IOException; +import java.io.InputStream; +import java.io.OutputStream; +import java.io.OutputStreamWriter; +import java.nio.charset.StandardCharsets; +import java.util.ArrayList; +import java.util.List; +import org.apache.hadoop.fs.Path; +import org.apache.iceberg.CombinedScanTask; +import org.apache.iceberg.DataOperations; +import org.apache.iceberg.FileScanTask; +import org.apache.iceberg.MicroBatches; +import org.apache.iceberg.MicroBatches.MicroBatch; +import org.apache.iceberg.Schema; +import org.apache.iceberg.SchemaParser; +import org.apache.iceberg.SerializableTable; +import org.apache.iceberg.Snapshot; +import org.apache.iceberg.Table; +import org.apache.iceberg.io.CloseableIterable; +import org.apache.iceberg.io.FileIO; +import org.apache.iceberg.io.InputFile; +import org.apache.iceberg.io.OutputFile; +import org.apache.iceberg.relocated.com.google.common.base.Preconditions; +import org.apache.iceberg.relocated.com.google.common.collect.Iterables; +import org.apache.iceberg.relocated.com.google.common.collect.Lists; +import org.apache.iceberg.spark.Spark3Util; +import org.apache.iceberg.spark.SparkReadOptions; +import org.apache.iceberg.spark.source.SparkBatchScan.ReadTask; +import org.apache.iceberg.spark.source.SparkBatchScan.ReaderFactory; +import org.apache.iceberg.util.PropertyUtil; +import org.apache.iceberg.util.SnapshotUtil; +import org.apache.iceberg.util.TableScanUtil; +import org.apache.spark.api.java.JavaSparkContext; +import org.apache.spark.broadcast.Broadcast; +import org.apache.spark.sql.connector.read.InputPartition; +import org.apache.spark.sql.connector.read.PartitionReaderFactory; +import org.apache.spark.sql.connector.read.streaming.MicroBatchStream; +import org.apache.spark.sql.connector.read.streaming.Offset; +import org.apache.spark.sql.util.CaseInsensitiveStringMap; + +import static org.apache.iceberg.TableProperties.SPLIT_LOOKBACK; +import static org.apache.iceberg.TableProperties.SPLIT_LOOKBACK_DEFAULT; +import static org.apache.iceberg.TableProperties.SPLIT_OPEN_FILE_COST; +import static org.apache.iceberg.TableProperties.SPLIT_OPEN_FILE_COST_DEFAULT; +import static org.apache.iceberg.TableProperties.SPLIT_SIZE; +import static org.apache.iceberg.TableProperties.SPLIT_SIZE_DEFAULT; + +public class SparkMicroBatchStream implements MicroBatchStream { + private final JavaSparkContext sparkContext; + private final Table table; + private final boolean caseSensitive; + private final Schema expectedSchema; + private final Long splitSize; + private final Integer splitLookback; + private final Long splitOpenFileCost; + private final boolean localityPreferred; + private final StreamingOffset initialOffset; + + SparkMicroBatchStream(JavaSparkContext sparkContext, + Table table, boolean caseSensitive, Schema expectedSchema, + CaseInsensitiveStringMap options, String checkpointLocation) { + this.sparkContext = sparkContext; + this.table = table; + this.caseSensitive = caseSensitive; + this.expectedSchema = expectedSchema; + this.localityPreferred = Spark3Util.isLocalityEnabled(table.io(), table.location(), options); + + long tableSplitSize = PropertyUtil.propertyAsLong(table.properties(), SPLIT_SIZE, SPLIT_SIZE_DEFAULT); + this.splitSize = Spark3Util.propertyAsLong(options, SparkReadOptions.SPLIT_SIZE, tableSplitSize); + + int tableSplitLookback = PropertyUtil.propertyAsInt(table.properties(), SPLIT_LOOKBACK, SPLIT_LOOKBACK_DEFAULT); + this.splitLookback = Spark3Util.propertyAsInt(options, SparkReadOptions.LOOKBACK, tableSplitLookback); + + long tableSplitOpenFileCost = PropertyUtil.propertyAsLong( + table.properties(), SPLIT_OPEN_FILE_COST, SPLIT_OPEN_FILE_COST_DEFAULT); + this.splitOpenFileCost = Spark3Util.propertyAsLong(options, SPLIT_OPEN_FILE_COST, tableSplitOpenFileCost); + + InitialOffsetStore initialOffsetStore = InitialOffsetStore.getInstance(table, checkpointLocation); + this.initialOffset = getOrWriteInitialOffset(initialOffsetStore); + } + + @Override + public Offset latestOffset() { + table.refresh(); + Snapshot latestSnapshot = table.currentSnapshot(); + if (latestSnapshot == null) { + return StreamingOffset.START_OFFSET; + } + + // a readStream on an Iceberg table can be started from 2 types of snapshots + // 1. a valid starting Snapshot: + // when this valid starting Snapshot is the initialOffset - then, scanAllFiles must be set to true; + // for all StreamingOffsets following this - scanAllFiles must be set to false + // 2. START_OFFSET: + // if the stream started on the table from START_OFFSET - it implies - that all the subsequent Snapshots added + // will have all files as net New manifests & hence scanAllFiles can be false. + boolean scanAllFiles = !StreamingOffset.START_OFFSET.equals(initialOffset) && + latestSnapshot.snapshotId() == initialOffset.snapshotId(); + + long filesNewlyAddedInLatestSnapshot = Iterables.size(latestSnapshot.addedFiles()); + long existingFilesInheritedByLatestSnapshot = SnapshotUtil.existingDataFiles(latestSnapshot); + long positionValue = scanAllFiles ? existingFilesInheritedByLatestSnapshot + filesNewlyAddedInLatestSnapshot : + filesNewlyAddedInLatestSnapshot; + + return new StreamingOffset(latestSnapshot.snapshotId(), positionValue, scanAllFiles); + } + + @Override + public InputPartition[] planInputPartitions(Offset start, Offset end) { + if (end.equals(StreamingOffset.START_OFFSET)) { + return new InputPartition[0]; + } + + // broadcast the table metadata as input partitions will be sent to executors + Broadcast<Table> tableBroadcast = sparkContext.broadcast(SerializableTable.copyOf(table)); + String expectedSchemaString = SchemaParser.toJson(expectedSchema); + + Preconditions.checkState( + end instanceof StreamingOffset, + "The end offset passed to planInputPartitions() is not an instance of StreamingOffset."); + + Preconditions.checkState( + start instanceof StreamingOffset, + "The start offset passed to planInputPartitions() is not an instance of StreamingOffset."); + + StreamingOffset endOffset = (StreamingOffset) end; + StreamingOffset startOffset = (StreamingOffset) start; + + List<FileScanTask> fileScanTasks = calculateFileScanTasks(startOffset, endOffset); + + CloseableIterable<FileScanTask> splitTasks = TableScanUtil.splitFiles( + CloseableIterable.withNoopClose(fileScanTasks), + splitSize); + List<CombinedScanTask> combinedScanTasks = Lists.newArrayList( + TableScanUtil.planTasks(splitTasks, splitSize, splitLookback, splitOpenFileCost)); + InputPartition[] readTasks = new InputPartition[combinedScanTasks.size()]; + + for (int i = 0; i < combinedScanTasks.size(); i++) { + readTasks[i] = new ReadTask( + combinedScanTasks.get(i), tableBroadcast, expectedSchemaString, + caseSensitive, localityPreferred); + } + + return readTasks; + } + + @Override + public PartitionReaderFactory createReaderFactory() { + return new ReaderFactory(0); + } + + @Override + public Offset initialOffset() { + return initialOffset; + } + + @Override + public Offset deserializeOffset(String json) { + return StreamingOffset.fromJson(json); + } + + @Override + public void commit(Offset end) { + } + + @Override + public void stop() { + } + + private static StreamingOffset getOrWriteInitialOffset(InitialOffsetStore initialOffsetStore) { + if (initialOffsetStore.isOffsetStoreInitialized()) { + return initialOffsetStore.getInitialOffset(); + } + + return initialOffsetStore.addInitialOffset(); + } + + private List<FileScanTask> calculateFileScanTasks(StreamingOffset startOffset, StreamingOffset endOffset) { + List<FileScanTask> fileScanTasks = new ArrayList<>(); + MicroBatch latestMicroBatch = null; + StreamingOffset batchStartOffset = StreamingOffset.START_OFFSET.equals(startOffset) ? + new StreamingOffset(SnapshotUtil.oldestSnapshot(table).snapshotId(), 0, false) : + startOffset; + + do { + final StreamingOffset currentOffset = + latestMicroBatch != null && latestMicroBatch.lastIndexOfSnapshot() ? + getNextAvailableSnapshot(latestMicroBatch.snapshotId()) : + batchStartOffset; + + latestMicroBatch = MicroBatches.from(table.snapshot(currentOffset.snapshotId()), table.io()) + .caseSensitive(caseSensitive) + .specsById(table.specs()) + .generate(currentOffset.position(), Long.MAX_VALUE, currentOffset.shouldScanAllFiles()); + + fileScanTasks.addAll(latestMicroBatch.tasks()); + } while (latestMicroBatch.snapshotId() != endOffset.snapshotId()); + + return fileScanTasks; + } + + private StreamingOffset getNextAvailableSnapshot(long snapshotId) { + Snapshot previousSnapshot = table.snapshot(snapshotId); + Snapshot pointer = table.currentSnapshot(); + while (pointer != null && previousSnapshot.snapshotId() != pointer.parentId()) { + Preconditions.checkState(pointer.operation().equals(DataOperations.APPEND), + "Encountered Snapshot DataOperation other than APPEND."); + + pointer = table.snapshot(pointer.parentId()); + } + + Preconditions.checkState(pointer != null, + "Cannot read data from snapshot which has already expired: %s", snapshotId); + + return new StreamingOffset(pointer.snapshotId(), 0L, false); + } + + interface InitialOffsetStore { + static InitialOffsetStore getInstance(Table table, String checkpointLocation) { + return new InitialOffsetStoreImpl(table, checkpointLocation); + } + + StreamingOffset addInitialOffset(); + + boolean isOffsetStoreInitialized(); + + StreamingOffset getInitialOffset(); + } + + private static class InitialOffsetStoreImpl implements InitialOffsetStore { + private final Table table; + private final FileIO io; + private final String initialOffsetLocation; + + InitialOffsetStoreImpl(Table table, String checkpointLocation) { + this.table = table; + this.io = table.io(); + this.initialOffsetLocation = new Path(checkpointLocation, "offsets/0").toString(); + } + + @Override + public StreamingOffset addInitialOffset() { Review comment: Yes, `START_OFFSET` is a valid initial offset - when the table is empty - by the time a streaming reader is created on the iceberg table. -- This is an automated message from the Apache Git Service. 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