Github user tdas commented on a diff in the pull request: https://github.com/apache/spark/pull/20096#discussion_r160006676 --- Diff: external/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/KafkaContinuousWriter.scala --- @@ -0,0 +1,113 @@ +/* + * 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 org.apache.kafka.clients.producer.{Callback, ProducerRecord, RecordMetadata} + +import org.apache.spark.internal.Logging +import org.apache.spark.sql.{Row, SparkSession} +import org.apache.spark.sql.catalyst.InternalRow +import org.apache.spark.sql.catalyst.expressions.{Attribute, Cast, Literal, UnsafeProjection} +import org.apache.spark.sql.kafka010.KafkaSourceProvider.{kafkaParamsForProducer, TOPIC_OPTION_KEY} +import org.apache.spark.sql.sources.v2.streaming.writer.ContinuousWriter +import org.apache.spark.sql.sources.v2.writer._ +import org.apache.spark.sql.streaming.OutputMode +import org.apache.spark.sql.types.{BinaryType, StringType, StructType} + +/** + * Dummy commit message. The DataSourceV2 framework requires a commit message implementation but we + * don't need to really send one. + */ +case object KafkaWriterCommitMessage extends WriterCommitMessage + +/** + * A [[ContinuousWriter]] for Kafka writing. Responsible for generating the writer factory. + * @param topic The topic this writer is responsible for. If None, topic will be inferred from + * a `topic` field in the incoming data. + * @param producerParams Parameters for Kafka producers in each task. + * @param schema The schema of the input data. + */ +class KafkaContinuousWriter( + topic: Option[String], producerParams: Map[String, String], schema: StructType) + extends ContinuousWriter with SupportsWriteInternalRow { + + override def createInternalRowWriterFactory(): KafkaContinuousWriterFactory = + KafkaContinuousWriterFactory(topic, producerParams, schema) + + override def commit(epochId: Long, messages: Array[WriterCommitMessage]): Unit = {} + override def abort(messages: Array[WriterCommitMessage]): Unit = {} +} + +/** + * A [[DataWriterFactory]] for Kafka writing. Will be serialized and sent to executors to generate + * the per-task data writers. + * @param topic The topic that should be written to. If None, topic will be inferred from + * a `topic` field in the incoming data. + * @param producerParams Parameters for Kafka producers in each task. + * @param schema The schema of the input data. + */ +case class KafkaContinuousWriterFactory( + topic: Option[String], producerParams: Map[String, String], schema: StructType) + extends DataWriterFactory[InternalRow] { + + override def createDataWriter(partitionId: Int, attemptNumber: Int): DataWriter[InternalRow] = { + new KafkaContinuousDataWriter(topic, producerParams, schema.toAttributes) + } +} + +/** + * A [[DataWriter]] for Kafka writing. One data writer will be created in each partition to + * process incoming rows. + * + * @param targetTopic The topic that this data writer is targeting. If None, topic will be inferred + * from a `topic` field in the incoming data. + * @param producerParams Parameters to use for the Kafka producer. + * @param inputSchema The attributes in the input data. + */ +class KafkaContinuousDataWriter( + targetTopic: Option[String], producerParams: Map[String, String], inputSchema: Seq[Attribute]) + extends KafkaRowWriter(inputSchema, targetTopic) with DataWriter[InternalRow] { + import scala.collection.JavaConverters._ + + private lazy val producer = CachedKafkaProducer.getOrCreate( + new java.util.HashMap[String, Object](producerParams.asJava)) + + def write(row: InternalRow): Unit = { + checkForErrors() + sendRow(row, producer) + } + + def commit(): WriterCommitMessage = { + // Send is asynchronous, but we can't commit until all rows are actually in Kafka. + // This requires flushing and then checking that no callbacks produced errors. + producer.flush() --- End diff -- maybe check for errors first before doing a flush and flush can take a long time and its better to fail earlier if possible.
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