Github user squito commented on a diff in the pull request: https://github.com/apache/spark/pull/7004#discussion_r34584417 --- Diff: core/src/main/scala/org/apache/spark/serializer/GenericAvroSerializer.scala --- @@ -0,0 +1,161 @@ +/* + * 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.serializer + +import java.io.ByteArrayOutputStream +import java.nio.ByteBuffer +import java.util.zip.{Inflater, Deflater} + +import scala.collection.mutable + +import com.esotericsoftware.kryo.{Kryo, Serializer => KSerializer} +import com.esotericsoftware.kryo.io.{Input => KryoInput, Output => KryoOutput} +import org.apache.avro.generic.{GenericData, GenericRecord} +import org.apache.avro.io._ +import org.apache.avro.{Schema, SchemaNormalization} + +object GenericAvroSerializer { + val avroSchemaNamespace = "avro.schema." + def avroSchemaKey(fingerprint: Long): String = avroSchemaNamespace + fingerprint +} + +/** + * Custom serializer used for generic Avro records. If the user registers the schemas + * ahead of time, then the schema's fingerprint will be sent with each message instead of the actual + * schema, as to reduce network IO. + * Actions like parsing or compressing schemas are computationally expensive so the serializer + * caches all previously seen values as to reduce the amount of work needed to do. + */ +class GenericAvroSerializer(schemas: Map[Long, String]) extends KSerializer[GenericRecord] { + + /** Used to reduce the amount of effort to compress the schema */ + private val compressCache = new mutable.HashMap[Schema, Array[Byte]]() + private val decompressCache = new mutable.HashMap[ByteBuffer, Schema]() + + /** Reuses the same datum reader/writer since the same schema will be used many times */ + private val writerCache = new mutable.HashMap[Schema, DatumWriter[_]]() + private val readerCache = new mutable.HashMap[Schema, DatumReader[_]]() + + /** Fingerprinting is very expensive to this alleviates most of the work */ + private val fingerprintCache = new mutable.HashMap[Schema, Long]() + private val schemaCache = new mutable.HashMap[Long, Schema]() + + private def getSchema(fingerprint: Long): Option[String] = schemas.get(fingerprint) + + /** + * Used to compress Schemas when they are being sent over the wire. + * The compression results are memoized to reduce the compression time since the + * same schema is compressed many times over + */ + def compress(schema: Schema): Array[Byte] = compressCache.getOrElseUpdate(schema, { + val deflater = new Deflater(Deflater.BEST_COMPRESSION) + val schemaBytes = schema.toString.getBytes("UTF-8") + deflater.setInput(schemaBytes) + deflater.finish() + val buffer = Array.ofDim[Byte](schemaBytes.length) + val outputStream = new ByteArrayOutputStream(schemaBytes.length) + while(!deflater.finished()) { + val count = deflater.deflate(buffer) + outputStream.write(buffer, 0, count) + } + outputStream.close() + outputStream.toByteArray + }) + + + /** + * Decompresses the schema into the actual in-memory object. Keeps an internal cache of already + * seen values so to limit the number of times that decompression has to be done. + */ + def decompress(schemaBytes: ByteBuffer): Schema = decompressCache.getOrElseUpdate(schemaBytes, { + val inflater = new Inflater() + val bytes = schemaBytes.array() + inflater.setInput(bytes) + val outputStream = new ByteArrayOutputStream(bytes.length) + val tmpBuffer = Array.ofDim[Byte](1024) + while (!inflater.finished()) { + val count = inflater.inflate(tmpBuffer) + outputStream.write(tmpBuffer, 0, count) + } + inflater.end() + outputStream.close() + new Schema.Parser().parse(new String(outputStream.toByteArray, "UTF-8")) + }) + + /** + * Serializes a record to the given output stream. It caches a lot of the internal data as + * to not redo work + */ + def serializeDatum[R <: GenericRecord](datum: R, output: KryoOutput): Unit = { + val encoder = EncoderFactory.get.binaryEncoder(output, null) + val schema = datum.getSchema + val fingerprint = fingerprintCache.getOrElseUpdate(schema, { + SchemaNormalization.parsingFingerprint64(schema) + }) + getSchema(fingerprint) match { + case Some(_) => { + output.writeBoolean(true) + output.writeLong(fingerprint) + } + case None => { + output.writeBoolean(false) + val compressedSchema = compress(schema) + output.writeInt(compressedSchema.length) + output.writeBytes(compressedSchema) + + } + } + + writerCache.getOrElseUpdate(schema, GenericData.get.createDatumWriter(schema)) + .asInstanceOf[DatumWriter[R]] + .write(datum, encoder) + encoder.flush() + } + + /** + * Deserializes generic records into their in-memory form. There is internal + * state to keep a cache of already seen schemas and datum readers. + */ + def deserializeDatum(input: KryoInput): GenericRecord = { + val schema = { + if (input.readBoolean()) { + val fingerprint = input.readLong() + schemaCache.getOrElseUpdate(fingerprint, { + getSchema(fingerprint) match { + case Some(s) => new Schema.Parser().parse(s) + case None => throw new RuntimeException(s"Unknown fingerprint: $fingerprint") + } + }) + } else { + val length = input.readInt() + decompress(ByteBuffer.wrap(input.readBytes(length))) + } + } + val decoder = DecoderFactory.get.directBinaryDecoder(input, null) + readerCache.getOrElseUpdate(schema, GenericData.get.createDatumReader(schema)) + .asInstanceOf[DatumReader[GenericRecord]] + .read(null.asInstanceOf[GenericRecord], decoder) --- End diff -- I think the `asInstanceOf` on `null` is unecessary
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