jerryshao commented on a change in pull request #796: URL: https://github.com/apache/iceberg/pull/796#discussion_r464868520
########## File path: spark2/src/main/java/org/apache/iceberg/spark/source/StreamingReader.java ########## @@ -0,0 +1,288 @@ +/* + * 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.util.Collections; +import java.util.List; +import java.util.Optional; +import java.util.stream.Collectors; +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.Snapshot; +import org.apache.iceberg.Table; +import org.apache.iceberg.encryption.EncryptionManager; +import org.apache.iceberg.io.CloseableIterable; +import org.apache.iceberg.io.FileIO; +import org.apache.iceberg.relocated.com.google.common.annotations.VisibleForTesting; +import org.apache.iceberg.relocated.com.google.common.base.Preconditions; +import org.apache.iceberg.relocated.com.google.common.collect.ImmutableList; +import org.apache.iceberg.relocated.com.google.common.collect.Lists; +import org.apache.iceberg.util.Pair; +import org.apache.iceberg.util.SnapshotUtil; +import org.apache.iceberg.util.TableScanUtil; +import org.apache.spark.broadcast.Broadcast; +import org.apache.spark.sql.sources.v2.DataSourceOptions; +import org.apache.spark.sql.sources.v2.reader.streaming.MicroBatchReader; +import org.apache.spark.sql.sources.v2.reader.streaming.Offset; +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +/** + * A mirco-batch based Spark Structured Streaming reader for Iceberg table. It will track the added + * files and generate tasks per batch to process newly added files. By default it will process + * all the newly added files to the current snapshot in each batch, user could also set this + * configuration "max-files-per-trigger" to control the number of files processed per batch. + */ +class StreamingReader extends Reader implements MicroBatchReader { + private static final Logger LOG = LoggerFactory.getLogger(StreamingReader.class); + + private StreamingOffset startOffset; + private StreamingOffset endOffset; + + private final Table table; + private final long maxSizePerBatch; + private final Long startSnapshotId; + + // Used to cache the pending batches for this streaming batch interval. + private Pair<StreamingOffset, List<MicroBatch>> cachedPendingBatches; + + StreamingReader(Table table, Broadcast<FileIO> io, Broadcast<EncryptionManager> encryptionManager, + boolean caseSensitive, DataSourceOptions options) { + super(table, io, encryptionManager, caseSensitive, options); + + this.table = table; + this.maxSizePerBatch = options.get("max-size-per-batch").map(Long::parseLong).orElse(Long.MAX_VALUE); + Preconditions.checkArgument(maxSizePerBatch > 0L, + "Option max-size-per-batch '%d' should > 0", maxSizePerBatch); + + this.startSnapshotId = options.get("starting-snapshot-id").map(Long::parseLong).orElse(null); + if (startSnapshotId != null) { + if (!SnapshotUtil.ancestorOf(table, table.currentSnapshot().snapshotId(), startSnapshotId)) { + throw new IllegalStateException("The option starting-snapshot-id " + startSnapshotId + + " is not an ancestor of the current snapshot"); + } + } + } + + @Override + @SuppressWarnings("unchecked") + public void setOffsetRange(Optional<Offset> start, Optional<Offset> end) { + table.refresh(); + + if (start.isPresent() && !StreamingOffset.START_OFFSET.equals(start.get())) { + this.startOffset = (StreamingOffset) start.get(); + this.endOffset = (StreamingOffset) end.orElse(calculateEndOffset(startOffset)); + } else { + // If starting offset is "START_OFFSET" (there's no snapshot in the last batch), or starting + // offset is not set, then we need to calculate the starting offset again. + this.startOffset = calculateStartingOffset(); + this.endOffset = calculateEndOffset(startOffset); + } + } + + @Override + public Offset getStartOffset() { + if (startOffset == null) { + throw new IllegalStateException("Start offset is not set"); + } + + return startOffset; + } + + @Override + public Offset getEndOffset() { + if (endOffset == null) { + throw new IllegalStateException("End offset is not set"); + } + + return endOffset; + } + + @Override + public Offset deserializeOffset(String json) { + return StreamingOffset.fromJson(json); + } + + @Override + public void commit(Offset end) { + // Since all the data and metadata of Iceberg is as it is, nothing needs to commit when + // offset is processed, so no need to implement this method. + } + + @Override + public void stop() {} + + @Override + public String toString() { + return String.format( + "IcebergStreamScan(table=%s, type=%s)", table, table.schema().asStruct()); + } + + @Override + @SuppressWarnings("unchecked") + protected List<CombinedScanTask> tasks() { + if (startOffset.equals(endOffset)) { + LOG.info("Start offset {} equals to end offset {}, no data to process", startOffset, endOffset); + return Collections.emptyList(); + } + + Preconditions.checkState(cachedPendingBatches != null, + "pendingBatches is null, which is unexpected as it will be set when calculating end offset"); + + List<MicroBatch> pendingBatches = cachedPendingBatches.second(); + if (pendingBatches.isEmpty()) { + LOG.info("There's no task to process in this batch"); + return Collections.emptyList(); + } + + MicroBatch lastBatch = pendingBatches.get(pendingBatches.size() - 1); + if (lastBatch.snapshotId() != endOffset.snapshotId() || lastBatch.endFileIndex() != endOffset.index()) { + throw new IllegalStateException("The cached pendingBatches doesn't match the current end offset " + endOffset); + } + + LOG.info("Processing data from {} to {}", startOffset, endOffset); + List<FileScanTask> tasks = pendingBatches.stream() + .flatMap(batch -> batch.tasks().stream()) + .collect(Collectors.toList()); + CloseableIterable<FileScanTask> splitTasks = TableScanUtil.splitFiles(CloseableIterable.withNoopClose(tasks), + splitSize()); + return Lists.newArrayList( + TableScanUtil.planTasks(splitTasks, splitSize(), splitLookback(), splitOpenFileCost())); + } + + private StreamingOffset calculateStartingOffset() { + StreamingOffset startingOffset; + if (startSnapshotId != null) { + startingOffset = new StreamingOffset(startSnapshotId, 0, true, false); + } else { + List<Long> snapshotIds = SnapshotUtil.currentAncestors(table); + if (snapshotIds.isEmpty()) { + // there's no snapshot currently. + startingOffset = StreamingOffset.START_OFFSET; + } else { + startingOffset = new StreamingOffset(snapshotIds.get(snapshotIds.size() - 1), 0, true, false); + } + } + + return startingOffset; + } + + private StreamingOffset calculateEndOffset(StreamingOffset start) { + if (start.equals(StreamingOffset.START_OFFSET)) { + return StreamingOffset.START_OFFSET; + } + + // Spark will invoke setOffsetRange more than once. If this is already calulated, use the cached one to avoid + // calculating again. + if (cachedPendingBatches == null || !cachedPendingBatches.first().equals(start)) { + this.cachedPendingBatches = Pair.of(start, getChangesWithRateLimit(start.snapshotId(), start.index(), + start.isStartingSnapshotId(), start.isLastIndexOfSnapshot(), maxSizePerBatch)); + } + + List<MicroBatch> batches = cachedPendingBatches.second(); + MicroBatch lastBatch = batches.isEmpty() ? null : batches.get(batches.size() - 1); + + if (lastBatch == null) { + return start; + } else { + boolean isStarting = lastBatch.snapshotId() == start.snapshotId() && start.isStartingSnapshotId(); + return new StreamingOffset(lastBatch.snapshotId(), lastBatch.endFileIndex(), isStarting, + lastBatch.lastIndexOfSnapshot()); + } + } + + @VisibleForTesting + @SuppressWarnings("checkstyle:CyclomaticComplexity") + List<MicroBatch> getChangesWithRateLimit(long snapshotId, int index, boolean isStarting, + boolean isLastIndexOfSnapshot, long maxSize) { + List<MicroBatch> batches = Lists.newArrayList(); + long currentLeftSize = maxSize; + MicroBatch lastBatch = null; + + if (!isLastIndexOfSnapshot && (isStarting || isValidSnapshot(table.snapshot(snapshotId)))) { + MicroBatch batch = MicroBatches.from(table.snapshot(snapshotId), table.io()) + .caseSensitive(super.caseSensitive()) + .specsById(table.specs()) + .generate(index, currentLeftSize, isStarting); + + batches.add(batch); + currentLeftSize -= batch.sizeInBytes(); + lastBatch = batch; + } + + // Current snapshot can already satisfy the size needs. + // Or DataFile size cannot satisfy the current needs of max size. For example: the request left size is 100, but the + // file size is 200, then file cannot add to this batch. + if (currentLeftSize <= 0L || (lastBatch != null && !lastBatch.lastIndexOfSnapshot())) { + return batches; + } + + long currentSnapshotId = table.currentSnapshot().snapshotId(); + if (currentSnapshotId == snapshotId) { + // the snapshot of current offset is already the latest snapshot of this table. + return batches; + } Review comment: `SnapshotUtil.snapshotIdsBetween` will not return an empty list, instead it will throw an exception when `from` and `to` snapshot is the same. So the code above is still required. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. 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