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https://issues.apache.org/jira/browse/FLINK-9808?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16662203#comment-16662203
]
ASF GitHub Bot commented on FLINK-9808:
---------------------------------------
StefanRRichter commented on a change in pull request #6875: [FLINK-9808] [state
backends] Migrate state when necessary in state backends
URL: https://github.com/apache/flink/pull/6875#discussion_r227761120
##########
File path:
flink-runtime/src/test/java/org/apache/flink/runtime/state/StateBackendMigrationTestBase.java
##########
@@ -0,0 +1,780 @@
+/*
+ * 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.runtime.state;
+
+import org.apache.flink.api.common.JobID;
+import org.apache.flink.api.common.state.ValueState;
+import org.apache.flink.api.common.state.ValueStateDescriptor;
+import org.apache.flink.api.common.typeutils.TypeSerializer;
+import org.apache.flink.api.common.typeutils.TypeSerializerSchemaCompatibility;
+import org.apache.flink.api.common.typeutils.TypeSerializerSnapshot;
+import org.apache.flink.api.common.typeutils.base.IntSerializer;
+import org.apache.flink.core.memory.DataInputView;
+import org.apache.flink.core.memory.DataOutputView;
+import org.apache.flink.runtime.checkpoint.CheckpointOptions;
+import org.apache.flink.runtime.checkpoint.StateObjectCollection;
+import org.apache.flink.runtime.execution.Environment;
+import org.apache.flink.runtime.operators.testutils.DummyEnvironment;
+import org.apache.flink.types.StringValue;
+import org.apache.flink.util.TestLogger;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.rules.ExpectedException;
+
+import java.io.IOException;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.concurrent.RunnableFuture;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * Tests for the {@link KeyedStateBackend} and {@link OperatorStateBackend} as
produced
+ * by various {@link StateBackend}s.
+ */
+@SuppressWarnings("serial")
+public abstract class StateBackendMigrationTestBase<B extends
AbstractStateBackend> extends TestLogger {
Review comment:
Overall, I find that this test tailored too much towards specific
implementation details, like how many times a certain serializer is called and
when. Learning from past mistakes, I found that such tests have a tendency to
break fast under future changes and wrongly produce test failures in the
absence of real bugs.
I would prefer if we could take a more "black box", for example maybe taking
one more checkpoint/restore cycle and providing a clearly incompatibel
serializer to see if the state was migrated for the checkpoint. This is more
stable against changes and tests what we actually want to make sure.
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> Implement state conversion procedure in state backends
> ------------------------------------------------------
>
> Key: FLINK-9808
> URL: https://issues.apache.org/jira/browse/FLINK-9808
> Project: Flink
> Issue Type: Sub-task
> Components: State Backends, Checkpointing
> Reporter: Tzu-Li (Gordon) Tai
> Assignee: Aljoscha Krettek
> Priority: Critical
> Labels: pull-request-available
> Fix For: 1.7.0
>
>
> With FLINK-9377 in place and that config snapshots serve as the single source
> of truth for recreating restore serializers, the next step would be to
> utilize this when performing a full-pass state conversion (i.e., read with
> old / restore serializer, write with new serializer).
> For Flink's heap-based backends, it can be seen that state conversion
> inherently happens, since all state is always deserialized after restore with
> the restore serializer, and written with the new serializer on snapshots.
> For the RocksDB state backend, since state is lazily deserialized, state
> conversion needs to happen for per-registered state on their first access if
> the registered new serializer has a different serialization schema than the
> previous serializer.
> This task should consist of three parts:
> 1. Allow {{CompatibilityResult}} to correctly distinguish between whether the
> new serializer's schema is a) compatible with the serializer as it is, b)
> compatible after the serializer has been reconfigured, or c) incompatible.
> 2. Introduce state conversion procedures in the RocksDB state backend. This
> should occur on the first state access.
> 3. Make sure that all other backends no longer do redundant serializer
> compatibility checks. That is not required because those backends always
> perform full-pass state conversions.
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