Pengzna commented on code in PR #11410: URL: https://github.com/apache/iotdb/pull/11410#discussion_r1375849429
########## iotdb-core/metrics/core/src/main/java/org/apache/iotdb/metrics/core/uitls/IoTDBCachedGauge.java: ########## @@ -0,0 +1,114 @@ +/* + * 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.iotdb.metrics.core.uitls; + +import org.apache.iotdb.metrics.core.uitls.IoTDBCachedGaugeMBean.AbstractJmxCachedGaugeMBean; +import org.apache.iotdb.metrics.type.AutoGauge; + +import com.codahale.metrics.Clock; + +import java.lang.ref.WeakReference; +import java.util.concurrent.TimeUnit; +import java.util.concurrent.atomic.AtomicLong; +import java.util.concurrent.atomic.AtomicReference; +import java.util.function.ToDoubleFunction; + +/** + * Gauges with cache, which have better performance in some read-intensive and calculation-intensive + * scenarios. Can be served as an additional option. + */ +public class IoTDBCachedGauge<T> extends AbstractJmxCachedGaugeMBean + implements AutoGauge, IoTDBCachedGaugeMBean { + /** The timer of metric system */ + private final Clock clock; + /** The time to reload cache */ + private final AtomicLong reloadAt; + /** The timeout duration */ + private final long timeoutNS; + /** The cache's value */ + private final AtomicReference<Double> value; + /** The reference object of gauge */ + private final WeakReference<T> refObj; + /** The calculate function of gauge */ + private final ToDoubleFunction<T> mapper; + + protected IoTDBCachedGauge( + WeakReference<T> refObj, ToDoubleFunction<T> mapper, long timeout, TimeUnit timeoutUnit) { + this(Clock.defaultClock(), refObj, mapper, timeout, timeoutUnit); + } + + protected IoTDBCachedGauge( + Clock clock, + WeakReference<T> refObj, + ToDoubleFunction<T> mapper, + long timeout, + TimeUnit timeoutUnit) { + this.clock = clock; + this.refObj = refObj; + this.mapper = mapper; + this.reloadAt = new AtomicLong(clock.getTick()); + this.timeoutNS = timeoutUnit.toNanos(timeout); + this.value = new AtomicReference<>(); + } + + @Override + public Number getValue() { + return this.value(); + } + + @Override + public double value() { + return getGaugeValue(); + } + + private double loadValue() { + if (refObj.get() == null) { + return 0d; + } + return mapper.applyAsDouble(refObj.get()); + } + + public double getGaugeValue() { + Double currentValue = this.value.get(); + // if cache expires or is not loaded, we update the cache with calculate function + if (shouldLoad() || currentValue == null) { + double newValue = loadValue(); + if (!this.value.compareAndSet(currentValue, newValue)) { + return this.value.get(); + } + return newValue; + } + // else we directly return the cache's value + return currentValue; Review Comment: Have fixed -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected]
