[jira] [Commented] (FLINK-9938) State TTL cleanup during full state scan upon checkpointing

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-9938?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16565221#comment-16565221 ] 

ASF GitHub Bot commented on FLINK-9938:
---------------------------------------

StefanRRichter commented on a change in pull request #6460: [FLINK-9938] Clean up full snapshot from expired state with TTL
URL: https://github.com/apache/flink/pull/6460#discussion_r206813225
 
 

 ##########
 File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/StateSnapshotFilter.java
 ##########
 @@ -0,0 +1,74 @@
+/*
+ * 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 javax.annotation.Nonnull;
+
+import java.util.Optional;
+
+/**
+ * Filter of snapshot state values.
+ *
+ * <p>This filter can be applied to state values
+ * to decide which entries should be included into the snapshot (can be modified before),
+ * others should be dropped (returns {@code Optional.empty()}).
+ */
+public interface StateSnapshotFilter<T> {
+	StateSnapshotFilter<?> SNAPSHOT_ALL = createSnapshotAll();
+
+	@SuppressWarnings("unchecked")
+	@Nonnull
+	static <T> StateSnapshotFilter<T> snapshotAll() {
+		return (StateSnapshotFilter<T>) SNAPSHOT_ALL;
+	}
+
+	static <T> StateSnapshotFilter<T> createSnapshotAll() {
+		return new StateSnapshotFilter<T>() {
+			@Override
+			@Nonnull
+			public Optional<T> filter(@Nonnull T value) {
+				return Optional.of(value);
+			}
+
+			@Override
+			@Nonnull
+			public Optional<byte[]> filterSerialized(@Nonnull byte[] value) {
+				return Optional.of(value);
+			}
+		};
+	}
+
+	/**
+	 * Filter by non-serialized form of value.
+	 *
+	 * @param value non-serialized form of value
+	 * @return Optional.of(value to snapshot) or Optional.empty() to drop
+	 */
+	@Nonnull
+	Optional<T> filter(@Nonnull T value);
 
 Review comment:
   What is the benefit of having an `Optional` here? I think the it gives not added value over making this simply `@Nullable`.

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> State TTL cleanup during full state scan upon checkpointing
> -----------------------------------------------------------
>
>                 Key: FLINK-9938
>                 URL: https://issues.apache.org/jira/browse/FLINK-9938
>             Project: Flink
>          Issue Type: Improvement
>          Components: State Backends, Checkpointing
>    Affects Versions: 1.6.0
>            Reporter: Andrey Zagrebin
>            Assignee: Andrey Zagrebin
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.6.0
>
>
> We can try to piggyback full state scan during certain checkpoint processes in backends, check TTL expiration for every entry and evict expired to speed up cleanup.



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