| /* |
| * 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.samza.metrics; |
| |
| import java.util.concurrent.atomic.AtomicReference; |
| |
| /** |
| * A Gauge is a {@link org.apache.samza.metrics.Metric} that wraps some instance of T in a thread-safe |
| * reference and allows it to be set or retrieved. Gauges record specific values over time. |
| * For example, the current length of a queue or the size of a buffer. |
| * |
| * @param <T> Instance to be wrapped in the gauge for metering. |
| */ |
| public class Gauge<T> implements Metric { |
| private final String name; |
| private AtomicReference<T> ref; |
| |
| public Gauge(String name, T value) { |
| this.name = name; |
| this.ref = new AtomicReference<T>(value); |
| } |
| |
| public boolean compareAndSet(T expected, T n) { |
| return ref.compareAndSet(expected, n); |
| } |
| |
| public T set(T n) { |
| return ref.getAndSet(n); |
| } |
| |
| public T getValue() { |
| return ref.get(); |
| } |
| |
| public String getName() { |
| return name; |
| } |
| |
| public void visit(MetricsVisitor visitor) { |
| visitor.gauge(this); |
| } |
| |
| public String toString() { |
| T value = ref.get(); |
| return (value == null) ? null : value.toString(); |
| } |
| } |