Github user squito commented on a diff in the pull request:
https://github.com/apache/spark/pull/7004#discussion_r33278696
--- Diff:
core/src/main/scala/org/apache/spark/serializer/GenericAvroSerializer.scala ---
@@ -0,0 +1,185 @@
+/*
+ * 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.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}
+
+import org.apache.spark.SparkConf
+
+import GenericAvroSerializer._
+
+object GenericAvroSerializer {
+ def avroSchemaKey(implicit fingerprint: Long): String =
s"avro.schema.$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(conf: SparkConf) extends
KSerializer[GenericRecord] {
+
+ private val serializer = serialize()
+ private val deserializer = deserialize()
+
+ private def confSchema(implicit fingerprint: Long) =
conf.getOption(avroSchemaKey)
+
+ /**
+ * 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 compressor(): Schema => Array[Byte] = {
+ val cache = new mutable.HashMap[Schema, Array[Byte]]()
+
--- End diff --
yeah I find this a little confusing. My initial thoughts on reading this
was that `compressor()` must be called multiple times, so that each one had its
own cache -- and then I was trying to track down where you'd reuse the cache
and where you'd use a new one. But actually one `GenericAvroSerializer` only
has one `compressCache`, one `writerCache`, one `decompressCache`, etc.
I understand wanting to limit the scoping of things, so I think you could
separate out the decompress & compress side into little helper classes if you
like. Though honestly I don't think there aren't that many variables and
functions, so IMO they could all be members of `GenericAvroSerializer` (with
most of them `private`).
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