flink-runtime/src/main/java/org/apache/flink/runtime/state/metrics/LatencyTrackingValueState.java

/*
 * 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.metrics;

import org.apache.flink.metrics.MetricGroup;
import org.apache.flink.runtime.state.internal.InternalValueState;

import java.io.IOException;

/**
 * This class wraps value state with latency tracking logic.
 *
 * @param <K> The type of key the state is associated to
 * @param <N> The type of the namespace
 * @param <T> Type of the user value of state
 */
class LatencyTrackingValueState<K, N, T>
        extends AbstractLatencyTrackState<
                K,
                N,
                T,
                InternalValueState<K, N, T>,
                LatencyTrackingValueState.ValueStateLatencyMetrics>
        implements InternalValueState<K, N, T> {

    public LatencyTrackingValueState(
            String stateName,
            InternalValueState<K, N, T> original,
            LatencyTrackingStateConfig latencyTrackingStateConfig) {
        super(
                original,
                new ValueStateLatencyMetrics(
                        stateName,
                        latencyTrackingStateConfig.getMetricGroup(),
                        latencyTrackingStateConfig.getSampleInterval(),
                        latencyTrackingStateConfig.getHistorySize()));
    }

    @Override
    public T value() throws IOException {
        if (latencyTrackingStateMetric.trackLatencyOnGet()) {
            return trackLatencyWithIOException(
                    () -> original.value(), ValueStateLatencyMetrics.VALUE_STATE_GET_LATENCY);
        } else {
            return original.value();
        }
    }

    @Override
    public void update(T value) throws IOException {
        if (latencyTrackingStateMetric.trackLatencyOnUpdate()) {
            trackLatencyWithIOException(
                    () -> original.update(value),
                    ValueStateLatencyMetrics.VALUE_STATE_UPDATE_LATENCY);
        } else {
            original.update(value);
        }
    }

    static class ValueStateLatencyMetrics extends StateLatencyMetricBase {
        private static final String VALUE_STATE_GET_LATENCY = "valueStateGetLatency";
        private static final String VALUE_STATE_UPDATE_LATENCY = "valueStateUpdateLatency";

        private int getCount = 0;
        private int updateCount = 0;

        private ValueStateLatencyMetrics(
                String stateName, MetricGroup metricGroup, int sampleInterval, int historySize) {
            super(stateName, metricGroup, sampleInterval, historySize);
        }

        int getGetCount() {
            return getCount;
        }

        int getUpdateCount() {
            return updateCount;
        }

        private boolean trackLatencyOnGet() {
            getCount = loopUpdateCounter(getCount);
            return getCount == 1;
        }

        private boolean trackLatencyOnUpdate() {
            updateCount = loopUpdateCounter(updateCount);
            return updateCount == 1;
        }
    }
}