spark KafkaSourceInitialOffsetWriter 源码
spark KafkaSourceInitialOffsetWriter 代码
文件路径：/connector/kafka-0-10-sql/src/main/scala/org/apache/spark/sql/kafka010/KafkaSourceInitialOffsetWriter.scala
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* 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
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package org.apache.spark.sql.kafka010
import java.io._
import java.nio.charset.StandardCharsets
import org.apache.commons.io.IOUtils
import org.apache.spark.sql.SparkSession
import org.apache.spark.sql.execution.streaming.{HDFSMetadataLog, SerializedOffset}
/** A version of [[HDFSMetadataLog]] specialized for saving the initial offsets. */
private[kafka010] class KafkaSourceInitialOffsetWriter(
sparkSession: SparkSession,
metadataPath: String)
extends HDFSMetadataLog[KafkaSourceOffset](sparkSession, metadataPath) {
val VERSION = 1
override def serialize(metadata: KafkaSourceOffset, out: OutputStream): Unit = {
out.write(0) // A zero byte is written to support Spark 2.1.0 (SPARK-19517)
val writer = new BufferedWriter(new OutputStreamWriter(out, StandardCharsets.UTF_8))
writer.write(s"v$VERSION\n")
writer.write(metadata.json)
writer.flush
}
override def deserialize(in: InputStream): KafkaSourceOffset = {
in.read() // A zero byte is read to support Spark 2.1.0 (SPARK-19517)
val content = IOUtils.toString(new InputStreamReader(in, StandardCharsets.UTF_8))
// HDFSMetadataLog guarantees that it never creates a partial file.
require(content.nonEmpty)
if (content(0) == 'v') {
val indexOfNewLine = content.indexOf("\n")
if (indexOfNewLine > 0) {
validateVersion(content.substring(0, indexOfNewLine), VERSION)
KafkaSourceOffset(SerializedOffset(content.substring(indexOfNewLine + 1)))
} else {
throw new IllegalStateException(
"Log file was malformed: failed to detect the log file version line.")
}
} else {
// The log was generated by Spark 2.1.0
KafkaSourceOffset(SerializedOffset(content))
}
}
}
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