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/*
* =========================================================================================
* Copyright © 2013-2015 the kamon project <http://kamon.io/>
*
* Licensed 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 kamon.annotation;
import java.lang.annotation.*;
/**
* A marker annotation to define a method as a Histogram.
* <p>
* <p>
* Given a method like this:
* <pre><code>
* {@literal @}0Histogram(name = "coolName", tags="${'my-cool-tag':'my-cool-value'}")
* public (Long|Double|Float|Integer) coolName() {
* return someComputation();
* }
* </code></pre>
* <p>
* <p>
* A {@link kamon.metric.instrument.Histogram Histogram} for the defining method with the name {@code coolName} will be created which uses the
* annotated method's return as its value.
*/
@Documented
@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Histogram {
/**
* @return The histogram's name.
* <p>
* Also, the Metric name can be resolved with an EL expression that evaluates to a String:
* <p>
* <pre>
* {@code
* class ClassWithHistogram {
* private long id;
*
* public long getId() { return id; }
*
* {@literal @}Histogram (name = "${'histoID:' += this.id}")
* void countedMethod() {} // create a histogram with name => histoID:[id]
* }
* }
* </pre>
*/
String name();
/**
* The lowest value that can be discerned (distinguished from 0) by the histogram.Must be a positive integer that
* is >= 1. May be internally rounded down to nearest power of 2.
*/
long lowestDiscernibleValue() default 1;
/**
* The highest value to be tracked by the histogram. Must be a positive integer that is >= (2 * lowestDiscernibleValue).
* Must not be larger than (Long.MAX_VALUE/2).
*/
long highestTrackableValue() default 3600000000000L;
/**
* The number of significant decimal digits to which the histogram will maintain value resolution and separation.
* Must be a non-negative integer between 1 and 3.
*/
int precision() default 2;
/**
* Tags are a way of adding dimensions to metrics,
* these are constructed using EL syntax e.g. "${'algorithm':'1','env':'production'}"
*
* @return the tags associated to the histogram
*/
String tags() default "";
}
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