com.hazelcast.internal.metrics.Probe Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2021, Hazelcast, Inc. All Rights Reserved.
*
* 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 com.hazelcast.internal.metrics;
import java.lang.annotation.Retention;
import java.lang.annotation.Target;
import static com.hazelcast.internal.metrics.ProbeLevel.INFO;
import static com.hazelcast.internal.metrics.ProbeUnit.COUNT;
import static java.lang.annotation.ElementType.FIELD;
import static java.lang.annotation.ElementType.METHOD;
import static java.lang.annotation.RetentionPolicy.RUNTIME;
/**
* Annotation that can be placed on a field or a method of an object to indicate
* that it should be tracked by the MetricsRegistry when the
* {@link MetricsRegistry#registerStaticMetrics(Object, String)} is called.
*
* The MetricsRegistry will automatically scan all interfaces and super classes
* of an object (recursively). So it is possible to define a Probe on e.g. an
* interface or an abstract class.
*
*
Prefer field
* Prefer placing the Probe to a field rather than to a method if the type is primitive.
* The {@link java.lang.reflect.Field} provides access to the actual field
* without the need for autoboxing. With the {@link java.lang.reflect.Method}
* a wrapper object is created when a primitive is returned by the method.
* Therefore, fields produce less garbage than methods.
*
* A Probe can be placed on fields or methods with the following (return) type:
*
* - byte
* - short
* - int
* - float
* - long
* - double
* - {@link java.util.concurrent.atomic.AtomicInteger}
* - {@link java.util.concurrent.atomic.AtomicLong}
* - {@link com.hazelcast.internal.util.counters.Counter}
* - {@link Byte}
* - {@link Short}
* - {@link Integer}
* - {@link Float}
* - {@link Double}
* - {@link java.util.Collection}: it will return the size
* - {@link java.util.Map}: it will return the size
* - {@link java.util.concurrent.Semaphore}: it will return the number of
* available permits
*
*
* If the field or method points to a null reference, it is interpreted as 0.
*/
@Retention(value = RUNTIME)
@Target({FIELD, METHOD })
public @interface Probe {
/**
* The name of the Probe.
*
* @return the name of the Probe.
*/
String name();
/**
* Returns the ProbeLevel.
*
* Using ProbeLevel one can indicate how 'important' this Probe is. This is
* useful to reduce memory overhead due to tracking of probes.
*
* @return the ProbeLevel.
*/
ProbeLevel level() default INFO;
/**
* Measurement unit of a Probe. Not used on member, becomes a part of the key.
*/
ProbeUnit unit() default COUNT;
/**
* Returns the targets excluded for this Probe. Used for filtering in
* {@link MetricsPublisher}s.
*
* The final excluded targets for a metric will be the union of the
* exclusions defined with this annotation and the exclusions defined
* on the {@link ExcludedMetricTargets}s annotation of the class
* containing the given Probe.
*
* @return the targets excluded for this Probe
* @see ExcludedMetricTargets
*/
MetricTarget[] excludedTargets() default {};
}