org.apache.spark.sql.execution.streaming.StreamMetadata.scala Maven / Gradle / Ivy
/*
* 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.execution.streaming
import java.io.{InputStreamReader, OutputStreamWriter}
import java.nio.charset.StandardCharsets
import scala.util.control.NonFatal
import org.apache.commons.io.IOUtils
import org.apache.hadoop.conf.Configuration
import org.apache.hadoop.fs.{FileSystem, FSDataInputStream, FSDataOutputStream, Path}
import org.json4s.NoTypeHints
import org.json4s.jackson.Serialization
import org.apache.spark.internal.Logging
import org.apache.spark.sql.streaming.StreamingQuery
/**
* Contains metadata associated with a [[StreamingQuery]]. This information is written
* in the checkpoint location the first time a query is started and recovered every time the query
* is restarted.
*
* @param id unique id of the [[StreamingQuery]] that needs to be persisted across restarts
*/
case class StreamMetadata(id: String) {
def json: String = Serialization.write(this)(StreamMetadata.format)
}
object StreamMetadata extends Logging {
implicit val format = Serialization.formats(NoTypeHints)
/** Read the metadata from file if it exists */
def read(metadataFile: Path, hadoopConf: Configuration): Option[StreamMetadata] = {
val fs = metadataFile.getFileSystem(hadoopConf)
if (fs.exists(metadataFile)) {
var input: FSDataInputStream = null
try {
input = fs.open(metadataFile)
val reader = new InputStreamReader(input, StandardCharsets.UTF_8)
val metadata = Serialization.read[StreamMetadata](reader)
Some(metadata)
} catch {
case NonFatal(e) =>
logError(s"Error reading stream metadata from $metadataFile", e)
throw e
} finally {
IOUtils.closeQuietly(input)
}
} else None
}
/** Write metadata to file */
def write(
metadata: StreamMetadata,
metadataFile: Path,
hadoopConf: Configuration): Unit = {
var output: FSDataOutputStream = null
try {
val fs = metadataFile.getFileSystem(hadoopConf)
output = fs.create(metadataFile)
val writer = new OutputStreamWriter(output)
Serialization.write(metadata, writer)
writer.close()
} catch {
case NonFatal(e) =>
logError(s"Error writing stream metadata $metadata to $metadataFile", e)
throw e
} finally {
IOUtils.closeQuietly(output)
}
}
}