vcrfxia commented on code in PR #13252:
URL: https://github.com/apache/kafka/pull/13252#discussion_r1114835088


##########
streams/src/main/java/org/apache/kafka/streams/state/internals/MeteredVersionedKeyValueStore.java:
##########
@@ -0,0 +1,227 @@
+/*
+ * 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.kafka.streams.state.internals;
+
+import static 
org.apache.kafka.streams.processor.internals.metrics.StreamsMetricsImpl.maybeMeasureLatency;
+
+import java.util.Objects;
+import org.apache.kafka.common.serialization.Serde;
+import org.apache.kafka.common.utils.Time;
+import org.apache.kafka.streams.errors.ProcessorStateException;
+import org.apache.kafka.streams.processor.ProcessorContext;
+import org.apache.kafka.streams.processor.StateStore;
+import org.apache.kafka.streams.processor.StateStoreContext;
+import org.apache.kafka.streams.processor.internals.SerdeGetter;
+import org.apache.kafka.streams.query.Position;
+import org.apache.kafka.streams.query.PositionBound;
+import org.apache.kafka.streams.query.Query;
+import org.apache.kafka.streams.query.QueryConfig;
+import org.apache.kafka.streams.query.QueryResult;
+import org.apache.kafka.streams.state.KeyValueStore;
+import org.apache.kafka.streams.state.TimestampedKeyValueStore;
+import org.apache.kafka.streams.state.ValueAndTimestamp;
+import org.apache.kafka.streams.state.VersionedBytesStore;
+import org.apache.kafka.streams.state.VersionedKeyValueStore;
+import org.apache.kafka.streams.state.VersionedRecord;
+
+/**
+ * A metered {@link VersionedKeyValueStore} wrapper that is used for recording 
operation
+ * metrics, and hence its inner {@link VersionedBytesStore} implementation 
does not need to provide
+ * its own metrics collecting functionality. The inner {@code 
VersionedBytesStore} of this class
+ * is a {@link KeyValueStore} of type <Bytes,byte[]>, so we use {@link 
Serde}s
+ * to convert from <K,ValueAndTimestamp<V&gt> to 
<Bytes,byte[]>. In particular,
+ * {@link NullableValueAndTimestampSerde} is used since putting a tombstone to 
a versioned key-value
+ * store requires putting a null value associated with a timestamp.
+ *
+ * @param <K> The key type
+ * @param <V> The (raw) value type
+ */
+public class MeteredVersionedKeyValueStore<K, V>
+    extends WrappedStateStore<VersionedBytesStore, K, V>
+    implements VersionedKeyValueStore<K, V> {
+
+    private final MeteredVersionedKeyValueStoreInternal internal;
+
+    MeteredVersionedKeyValueStore(final VersionedBytesStore inner,
+                                  final String metricScope,
+                                  final Time time,
+                                  final Serde<K> keySerde,
+                                  final Serde<ValueAndTimestamp<V>> 
valueSerde) {
+        super(inner);
+        internal = new MeteredVersionedKeyValueStoreInternal(inner, 
metricScope, time, keySerde, valueSerde);
+    }
+
+    /**
+     * Private helper class which represents the functionality of a {@link 
VersionedKeyValueStore}
+     * as a {@link TimestampedKeyValueStore} so that the bulk of the metering 
logic may be
+     * inherited from {@link MeteredKeyValueStore}. As a result, the 
implementation of
+     * {@link MeteredVersionedKeyValueStore} is a simple wrapper to translate 
from this
+     * {@link TimestampedKeyValueStore} representation of a versioned 
key-value store into the
+     * {@link VersionedKeyValueStore} interface itself.

Review Comment:
   Thanks for the suggestions! Incorporated this into the latest commit. I used 
`KeyValueStore` in the comments instead of `TimestampedKeyValueStore` (pending 
our other discussion about whether `MeteredVersionedKeyValueStore` is 
conceptually `MeteredTimestampedKeyValueStore` or `MeteredKeyValueStore`) and 
also modified the last line since I wasn't sure which `get()` override you were 
referring to.



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