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https://issues.apache.org/jira/browse/FLINK-8802?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16398261#comment-16398261
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ASF GitHub Bot commented on FLINK-8802:
---------------------------------------
Github user zentol commented on a diff in the pull request:
https://github.com/apache/flink/pull/5691#discussion_r174383043
--- Diff:
flink-runtime/src/main/java/org/apache/flink/runtime/query/KvStateEntry.java ---
@@ -0,0 +1,79 @@
+/*
+ * 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.query;
+
+import org.apache.flink.annotation.Internal;
+import org.apache.flink.annotation.VisibleForTesting;
+import org.apache.flink.runtime.state.internal.InternalKvState;
+import org.apache.flink.util.Preconditions;
+
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ConcurrentMap;
+
+/**
+ * An entry holding the {@link InternalKvState} along with its {@link
KvStateInfo}.
+ *
+ * @param <K> The type of key the state is associated to
+ * @param <N> The type of the namespace the state is associated to
+ * @param <V> The type of values kept internally in state
+ */
+@Internal
+public class KvStateEntry<K, N, V> {
+
+ private final InternalKvState<K, N, V> state;
+ private final KvStateInfo<K, N, V> stateInfo;
+
+ private final ConcurrentMap<Thread, KvStateInfo<K, N, V>>
serializerCache;
+
+ public KvStateEntry(final InternalKvState<K, N, V> state) {
+
+ this.state = Preconditions.checkNotNull(state);
+ this.stateInfo = new KvStateInfo<>(
+ state.getKeySerializer(),
+ state.getNamespaceSerializer(),
+ state.getValueSerializer()
+ );
+
+ this.serializerCache =
+ stateInfo.duplicate() == stateInfo
+ ? null
// if the serializers are stateless, we do not need a
cache
--- End diff --
An empty map would be acceptable here.
> Concurrent serialization without duplicating serializers in state server.
> -------------------------------------------------------------------------
>
> Key: FLINK-8802
> URL: https://issues.apache.org/jira/browse/FLINK-8802
> Project: Flink
> Issue Type: Bug
> Components: Queryable State
> Affects Versions: 1.5.0
> Reporter: Kostas Kloudas
> Assignee: Kostas Kloudas
> Priority: Blocker
> Fix For: 1.5.0
>
>
> The `getSerializedValue()` may be called by multiple threads but serializers
> are not duplicated, which may lead to exceptions thrown when a serializer is
> stateful.
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