[GitHub] [flink-statefun] sjwiesman commented on a change in pull request #113: [Flink-17644] Add state expiration to the Java SDK

[GitBox <gi...@apache.org>]

sjwiesman commented on a change in pull request #113:
URL: https://github.com/apache/flink-statefun/pull/113#discussion_r426782885



##########
File path: statefun-sdk/src/main/java/org/apache/flink/statefun/sdk/state/Expiration.java
##########
@@ -0,0 +1,83 @@
+/*
+ * 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.statefun.sdk.state;
+
+import java.time.Duration;
+import java.util.Objects;
+
+/**
+ * State Expiration Configuration
+ *
+ * <p>This class defines the way state can be auto expired by the runtime. State expiration (also
+ * known as state TTL) can be used to keep state from growing arbitrarily by assigning an expiration
+ * date to a {@link PersistedAppendingBuffer}, {@link PersistedValue} or a {@link PersistedTable}.
+ *
+ * <p>State can be expired after a duration had passed since either from the last write to the
+ * state, or the last read.
+ */
+public final class Expiration {
+  public enum Mode {
+    NONE,
+    AFTER_WRITE,
+    AFTER_READ_OR_WRITE;
+  }
+
+  /**
+   * Returns an Expiration configuration that would expire a @duration after the last write.
+   *
+   * @param duration a duration to wait before considering the state expired.
+   */
+  public static Expiration expireAfterWriting(Duration duration) {
+    return new Expiration(Mode.AFTER_WRITE, duration);
+  }
+
+  /**
+   * Returns an Expiration configuration that would expire a @duration after the last write or read.
+   *
+   * @param duration a duration to wait before considering the state expired.
+   */
+  public static Expiration expireAfterReadingOrWriting(Duration duration) {
+    return new Expiration(Mode.AFTER_READ_OR_WRITE, duration);
+  }
+
+  public static Expiration expireAfter(Duration duration, Mode mode) {
+    return new Expiration(mode, duration);
+  }
+
+  /** @return Returns a disabled expiration */
+  public static Expiration none() {
+    return new Expiration(Mode.NONE, Duration.ZERO);
+  }
+
+  private final Mode mode;
+  private final Duration duration;
+
+  public Expiration(Mode mode, Duration duration) {

Review comment:
       ?
   ```suggestion
     private Expiration(Mode mode, Duration duration) {
   ```




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