[GitHub] tzulitai commented on a change in pull request #6711: [FLINK-9377] [core, state backends] Remove serializers from checkpoints

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tzulitai commented on a change in pull request #6711: [FLINK-9377] [core, state backends] Remove serializers from checkpoints
URL: https://github.com/apache/flink/pull/6711#discussion_r222594575
 
 

 ##########
 File path: flink-core/src/main/java/org/apache/flink/api/common/typeutils/TypeSerializerConfigSnapshotSerializationUtil.java
 ##########
 @@ -0,0 +1,172 @@
+/*
+ * 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.flink.api.common.typeutils;
+
+import org.apache.flink.core.io.VersionedIOReadableWritable;
+import org.apache.flink.core.memory.DataInputView;
+import org.apache.flink.core.memory.DataOutputView;
+import org.apache.flink.util.InstantiationUtil;
+import org.apache.flink.util.Preconditions;
+
+import java.io.IOException;
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * Utility methods for serialization of {@link TypeSerializerConfigSnapshot}.
+ */
+public class TypeSerializerConfigSnapshotSerializationUtil {
+
+	/**
+	 * Writes a {@link TypeSerializerConfigSnapshot} to the provided data output view.
+	 *
+	 * <p>It is written with a format that can be later read again using
+	 * {@link #readSerializerConfigSnapshot(DataInputView, ClassLoader)}.
+	 *
+	 * @param out the data output view
+	 * @param serializerConfigSnapshot the serializer configuration snapshot to write
+	 *
+	 * @throws IOException
+	 */
+	public static <T> void writeSerializerConfigSnapshot(
+		DataOutputView out,
+		TypeSerializerConfigSnapshot<T> serializerConfigSnapshot,
+		TypeSerializer<T> serializer) throws IOException {
+
+		new TypeSerializerConfigSnapshotSerializationProxy<>(serializerConfigSnapshot, serializer).write(out);
+	}
+
+	/**
+	 * Reads from a data input view a {@link TypeSerializerConfigSnapshot} that was previously
+	 * written using {@link TypeSerializerConfigSnapshotSerializationUtil#writeSerializerConfigSnapshot(DataOutputView, TypeSerializerConfigSnapshot, TypeSerializer)}.
+	 *
+	 * @param in the data input view
+	 * @param userCodeClassLoader the user code class loader to use
+	 *
+	 * @return the read serializer configuration snapshot
+	 *
+	 * @throws IOException
+	 */
+	public static TypeSerializerConfigSnapshot readSerializerConfigSnapshot(
+			DataInputView in,
+			ClassLoader userCodeClassLoader) throws IOException {
+
+		final TypeSerializerConfigSnapshotSerializationProxy proxy = new TypeSerializerConfigSnapshotSerializationProxy(userCodeClassLoader);
+		proxy.read(in);
+
+		return proxy.getSerializerConfigSnapshot();
+	}
+
+	/**
+	 * Reads from a data input view multiple {@link TypeSerializerConfigSnapshot}s that was previously
+	 * written using {@link TypeSerializerConfigSnapshotSerializationUtil#writeSerializerConfigSnapshot(DataOutputView, TypeSerializerConfigSnapshot, TypeSerializer)}.
+	 *
+	 * @param in the data input view
+	 * @param userCodeClassLoader the user code class loader to use
+	 *
+	 * @return the read serializer configuration snapshots
+	 *
+	 * @throws IOException
+	 */
+	public static List<TypeSerializerConfigSnapshot<?>> readSerializerConfigSnapshots(
+			DataInputView in,
+			ClassLoader userCodeClassLoader) throws IOException {
+
+		int numFields = in.readInt();
+		final List<TypeSerializerConfigSnapshot<?>> serializerConfigSnapshots = new ArrayList<>(numFields);
+
+		TypeSerializerConfigSnapshotSerializationProxy proxy;
+		for (int i = 0; i < numFields; i++) {
+			proxy = new TypeSerializerConfigSnapshotSerializationProxy(userCodeClassLoader);
+			proxy.read(in);
+			serializerConfigSnapshots.add(proxy.getSerializerConfigSnapshot());
+		}
+
+		return serializerConfigSnapshots;
+	}
+
+	/**
+	 * Utility serialization proxy for a {@link TypeSerializerConfigSnapshot}.
+	 */
+	static final class TypeSerializerConfigSnapshotSerializationProxy<T> extends VersionedIOReadableWritable {
+
+		private static final int VERSION = 1;
+
+		private ClassLoader userCodeClassLoader;
+		private TypeSerializerConfigSnapshot<T> serializerConfigSnapshot;
+		private TypeSerializer<T> serializer;
+
+		TypeSerializerConfigSnapshotSerializationProxy(ClassLoader userCodeClassLoader) {
+			this.userCodeClassLoader = Preconditions.checkNotNull(userCodeClassLoader);
+		}
+
+		TypeSerializerConfigSnapshotSerializationProxy(
+			TypeSerializerConfigSnapshot<T> serializerConfigSnapshot,
+			TypeSerializer<T> serializer) {
+			this.serializerConfigSnapshot = Preconditions.checkNotNull(serializerConfigSnapshot);
+			this.serializer = Preconditions.checkNotNull(serializer);
+		}
+
+		@Override
+		public void write(DataOutputView out) throws IOException {
+			super.write(out);
+
+			// config snapshot class, so that we can re-instantiate the
+			// correct type of config snapshot instance when deserializing
+			out.writeUTF(serializerConfigSnapshot.getClass().getName());
+
+			// TODO this is a temporary workaround until all serializer config snapshot classes in Flink
+			// TODO have properly implemented the restore serializer factory methods
+			serializerConfigSnapshot.setSerializer(serializer);
+
+			// the actual configuration parameters
+			serializerConfigSnapshot.write(out);
+		}
+
+		@SuppressWarnings("unchecked")
+		@Override
+		public void read(DataInputView in) throws IOException {
+			super.read(in);
+
+			String serializerConfigClassname = in.readUTF();
+			Class<? extends TypeSerializerConfigSnapshot> serializerConfigSnapshotClass;
+			try {
+				serializerConfigSnapshotClass = (Class<? extends TypeSerializerConfigSnapshot>)
+					Class.forName(serializerConfigClassname, true, userCodeClassLoader);
+			} catch (ClassNotFoundException e) {
+				throw new IOException(
+					"Could not find requested TypeSerializerConfigSnapshot class "
+						+ serializerConfigClassname +  " in classpath.", e);
+			}
+
+			serializerConfigSnapshot = InstantiationUtil.instantiate(serializerConfigSnapshotClass);
+			serializerConfigSnapshot.setUserCodeClassLoader(userCodeClassLoader);
 
 Review comment:
   I suggest that this goes as a follow-up PR.

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