HeartSaVioR commented on a change in pull request #24173: [SPARK-27237][SS]
Introduce State schema validation among query restart
URL: https://github.com/apache/spark/pull/24173#discussion_r267976417
##########
File path:
sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/state/StateStore.scala
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@@ -477,5 +487,73 @@ object StateStore extends Logging {
None
}
}
-}
+ private class StateSchemaCompatibilityChecker(
+ providerId: StateStoreProviderId,
+ hadoopConf: Configuration) {
+
+ private val storeCpLocation = providerId.storeId.storeCheckpointLocation()
+ private val fm = CheckpointFileManager.create(storeCpLocation, hadoopConf)
+ private val schemaFileLocation = schemaFile(storeCpLocation)
+
+ fm.mkdirs(schemaFileLocation.getParent)
+
+ def check(keySchema: StructType, valueSchema: StructType): Unit = {
+ if (fm.exists(schemaFileLocation)) {
+ logDebug(s"Schema file for provider $providerId exists. Comparing with
provided schema.")
+ val (storedKeySchema, storedValueSchema) = readSchemaFile()
+
+ def typesEq(schema1: StructType, schema2: StructType): Boolean = {
+ val fieldToType: StructField => (DataType, Boolean) = f =>
(f.dataType, f.nullable)
+ (schema1.length == schema2.length) &&
+ schema1.map(fieldToType).equals(schema2.map(fieldToType))
+ }
+
+ val errorMsg = "Provided schema doesn't match to the schema for
existing state! " +
+ "Please note that Spark allow difference of field name: check count
of fields " +
+ "and data type of each field.\n" +
+ s"- provided schema: key $keySchema value $valueSchema\n" +
+ s"- existing schema: key $storedKeySchema value $storedValueSchema\n"
+
+ if (!typesEq(keySchema, storedKeySchema) || !typesEq(valueSchema,
storedValueSchema)) {
+ logError(errorMsg)
+ throw new IllegalStateException(errorMsg)
+ }
+ } else {
+ // schema doesn't exist, create one now
+ logDebug(s"Schema file for provider $providerId doesn't exist.
Creating one.")
+ createSchemaFile(keySchema, valueSchema)
+ }
+ }
+
+ private def readSchemaFile(): (StructType, StructType) = {
+ val inStream = fm.open(schemaFileLocation)
+ val br = new BufferedReader(new InputStreamReader(inStream))
+
+ try {
+ val keySchemaStr = inStream.readUTF().stripSuffix("\n")
+ val valueSchemaStr = inStream.readUTF().stripSuffix("\n")
+
+ (StructType.fromString(keySchemaStr),
StructType.fromString(valueSchemaStr))
+ } finally {
+ br.close()
+ }
+ }
+
+ private def createSchemaFile(keySchema: StructType, valueSchema:
StructType): Unit = {
+ val outStream = fm.createAtomic(schemaFileLocation, overwriteIfPossible
= true)
+ try {
+ outStream.writeUTF(keySchema.json + "\n")
+ outStream.writeUTF(valueSchema.json + "\n")
+ outStream.close()
+ } catch { case NonFatal(e) =>
+ logError(s"Fail to write schema file to $schemaFileLocation", e)
+ outStream.cancel()
+ throw e
+ }
+ }
+ }
+
+ private def schemaFile(storeCpLocation: Path): Path =
+ new Path(new Path(storeCpLocation, "_metadata"), "schema")
Review comment:
So this file will be created and maintained per partition which will avoid
concurrent read/write issue, but may not sound good since it's redundant.
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