[GitHub] spark pull request #20253: [SPARK-22908][SS] Roll forward continuous process...

[tdas <gi...@git.apache.org>]

Github user tdas commented on a diff in the pull request:

    https://github.com/apache/spark/pull/20253#discussion_r161357488
  
    --- Diff: external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/KafkaContinuousReader.scala ---
    @@ -0,0 +1,253 @@
    +/*
    + * 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.spark.sql.kafka010
    +
    +import java.{util => ju}
    +import java.util.concurrent.TimeoutException
    +
    +import org.apache.kafka.clients.consumer.{ConsumerRecord, OffsetOutOfRangeException}
    +import org.apache.kafka.common.TopicPartition
    +
    +import org.apache.spark.TaskContext
    +import org.apache.spark.internal.Logging
    +import org.apache.spark.sql.SparkSession
    +import org.apache.spark.sql.catalyst.expressions.UnsafeRow
    +import org.apache.spark.sql.catalyst.expressions.codegen.{BufferHolder, UnsafeRowWriter}
    +import org.apache.spark.sql.catalyst.util.DateTimeUtils
    +import org.apache.spark.sql.kafka010.KafkaSource.{INSTRUCTION_FOR_FAIL_ON_DATA_LOSS_FALSE, INSTRUCTION_FOR_FAIL_ON_DATA_LOSS_TRUE}
    +import org.apache.spark.sql.sources.v2.reader._
    +import org.apache.spark.sql.sources.v2.streaming.reader.{ContinuousDataReader, ContinuousReader, Offset, PartitionOffset}
    +import org.apache.spark.sql.types.StructType
    +import org.apache.spark.unsafe.types.UTF8String
    +
    +/**
    + * A [[ContinuousReader]] for data from kafka.
    + *
    + * @param offsetReader  a reader used to get kafka offsets. Note that the actual data will be
    + *                      read by per-task consumers generated later.
    + * @param kafkaParams   String params for per-task Kafka consumers.
    + * @param sourceOptions The [[org.apache.spark.sql.sources.v2.DataSourceV2Options]] params which
    + *                      are not Kafka consumer params.
    + * @param metadataPath Path to a directory this reader can use for writing metadata.
    + * @param initialOffsets The Kafka offsets to start reading data at.
    + * @param failOnDataLoss Flag indicating whether reading should fail in data loss
    + *                       scenarios, where some offsets after the specified initial ones can't be
    + *                       properly read.
    + */
    +class KafkaContinuousReader(
    +    offsetReader: KafkaOffsetReader,
    +    kafkaParams: ju.Map[String, Object],
    +    sourceOptions: Map[String, String],
    +    metadataPath: String,
    +    initialOffsets: KafkaOffsetRangeLimit,
    +    failOnDataLoss: Boolean)
    +  extends ContinuousReader with SupportsScanUnsafeRow with Logging {
    +
    +  private lazy val session = SparkSession.getActiveSession.get
    +  private lazy val sc = session.sparkContext
    +
    +  // Initialized when creating read tasks. If this diverges from the partitions at the latest
    +  // offsets, we need to reconfigure.
    +  // Exposed outside this object only for unit tests.
    +  private[sql] var knownPartitions: Set[TopicPartition] = _
    +
    +  override def readSchema: StructType = KafkaOffsetReader.kafkaSchema
    +
    +  private var offset: Offset = _
    +  override def setOffset(start: ju.Optional[Offset]): Unit = {
    +    offset = start.orElse {
    +      val offsets = initialOffsets match {
    +        case EarliestOffsetRangeLimit => KafkaSourceOffset(offsetReader.fetchEarliestOffsets())
    +        case LatestOffsetRangeLimit => KafkaSourceOffset(offsetReader.fetchLatestOffsets())
    +        case SpecificOffsetRangeLimit(p) => offsetReader.fetchSpecificOffsets(p, reportDataLoss)
    +      }
    +      logInfo(s"Initial offsets: $offsets")
    +      offsets
    +    }
    +  }
    +
    +  override def getStartOffset(): Offset = offset
    +
    +  override def deserializeOffset(json: String): Offset = {
    +    KafkaSourceOffset(JsonUtils.partitionOffsets(json))
    +  }
    +
    +  override def createUnsafeRowReadTasks(): ju.List[ReadTask[UnsafeRow]] = {
    +    import scala.collection.JavaConverters._
    +
    +    val oldStartPartitionOffsets = KafkaSourceOffset.getPartitionOffsets(offset)
    +
    +    val currentPartitionSet = offsetReader.fetchEarliestOffsets().keySet
    +    val newPartitions = currentPartitionSet.diff(oldStartPartitionOffsets.keySet)
    +    val newPartitionOffsets = offsetReader.fetchEarliestOffsets(newPartitions.toSeq)
    +
    +    val deletedPartitions = oldStartPartitionOffsets.keySet.diff(currentPartitionSet)
    +    if (deletedPartitions.nonEmpty) {
    +      reportDataLoss(s"Some partitions were deleted: $deletedPartitions")
    +    }
    +
    +    val startOffsets = newPartitionOffsets ++
    +      oldStartPartitionOffsets.filterKeys(!deletedPartitions.contains(_))
    +    knownPartitions = startOffsets.keySet
    +
    +    startOffsets.toSeq.map {
    +      case (topicPartition, start) =>
    +        KafkaContinuousReadTask(
    +          topicPartition, start, kafkaParams, failOnDataLoss)
    +          .asInstanceOf[ReadTask[UnsafeRow]]
    +    }.asJava
    +  }
    +
    +  /** Stop this source and free any resources it has allocated. */
    +  def stop(): Unit = synchronized {
    +    offsetReader.close()
    +  }
    +
    +  override def commit(end: Offset): Unit = {}
    +
    +  override def mergeOffsets(offsets: Array[PartitionOffset]): Offset = {
    +    val mergedMap = offsets.map {
    +      case KafkaSourcePartitionOffset(p, o) => Map(p -> o)
    +    }.reduce(_ ++ _)
    +    KafkaSourceOffset(mergedMap)
    +  }
    +
    +  override def needsReconfiguration(): Boolean = {
    +    knownPartitions != null && offsetReader.fetchLatestOffsets().keySet != knownPartitions
    +  }
    +
    +  override def toString(): String = s"KafkaSource[$offsetReader]"
    +
    +  /**
    +   * If `failOnDataLoss` is true, this method will throw an `IllegalStateException`.
    +   * Otherwise, just log a warning.
    +   */
    +  private def reportDataLoss(message: String): Unit = {
    +    if (failOnDataLoss) {
    +      throw new IllegalStateException(message + s". $INSTRUCTION_FOR_FAIL_ON_DATA_LOSS_TRUE")
    +    } else {
    +      logWarning(message + s". $INSTRUCTION_FOR_FAIL_ON_DATA_LOSS_FALSE")
    +    }
    +  }
    +}
    +
    +/**
    + * A read task for continuous Kafka processing. This will be serialized and transformed into a
    + * full reader on executors.
    + *
    + * @param topicPartition The (topic, partition) pair this task is responsible for.
    + * @param startOffset The offset to start reading from within the partition.
    + * @param kafkaParams Kafka consumer params to use.
    + * @param failOnDataLoss Flag indicating whether data reader should fail if some offsets
    + *                       are skipped.
    + */
    +case class KafkaContinuousReadTask(
    +    topicPartition: TopicPartition,
    +    startOffset: Long,
    +    kafkaParams: ju.Map[String, Object],
    +    failOnDataLoss: Boolean) extends ReadTask[UnsafeRow] {
    +  override def createDataReader(): KafkaContinuousDataReader = {
    +    new KafkaContinuousDataReader(topicPartition, startOffset, kafkaParams, failOnDataLoss)
    +  }
    +}
    +
    +/**
    + * A per-task data reader for continuous Kafka processing.
    + *
    + * @param topicPartition The (topic, partition) pair this data reader is responsible for.
    + * @param startOffset The offset to start reading from within the partition.
    + * @param kafkaParams Kafka consumer params to use.
    + * @param failOnDataLoss Flag indicating whether data reader should fail if some offsets
    + *                       are skipped.
    + */
    +class KafkaContinuousDataReader(
    +    topicPartition: TopicPartition,
    +    startOffset: Long,
    +    kafkaParams: ju.Map[String, Object],
    +    failOnDataLoss: Boolean) extends ContinuousDataReader[UnsafeRow] {
    +  private val topic = topicPartition.topic
    +  private val kafkaPartition = topicPartition.partition
    +  private val consumer = CachedKafkaConsumer.createUncached(topic, kafkaPartition, kafkaParams)
    +
    +  private val sharedRow = new UnsafeRow(7)
    +  private val bufferHolder = new BufferHolder(sharedRow)
    +  private val rowWriter = new UnsafeRowWriter(bufferHolder, 7)
    +
    +  private var nextKafkaOffset = startOffset
    +  private var currentRecord: ConsumerRecord[Array[Byte], Array[Byte]] = _
    +
    +  override def next(): Boolean = {
    +    var r: ConsumerRecord[Array[Byte], Array[Byte]] = null
    +    while (r == null) {
    +      if (TaskContext.get().isInterrupted() || TaskContext.get().isCompleted()) return false
    +      // Our consumer.get is not interruptible, so we have to set a low poll timeout, leaving
    +      // interrupt points to end the query rather than waiting for new data that might never come.
    +      try {
    +        r = consumer.get(
    +          nextKafkaOffset,
    +          untilOffset = Long.MaxValue,
    +          pollTimeoutMs = 1000,
    +          failOnDataLoss)
    +      } catch {
    +        // We didn't read within the timeout. We're supposed to block indefinitely for new data, so
    +        // swallow and ignore this.
    +        case _: TimeoutException =>
    +        // This is a failOnDataLoss exception. Retry if nextKafkaOffset is within the data range,
    --- End diff --
    
    add an empty line to distinguish that comment below this belongs to next case


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