com.hazelcast.internal.metrics.Probe Maven / Gradle / Ivy
/*
* Copyright (c) 2008-2016, 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 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 method of an object to indicate that it should be tracked by the
* MetricsRegistry when the {@link MetricsRegistry#scanAndRegister(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 abstract class.
*
* Prefer field
* Prefer placing a Probe to a field above a method if the type is a 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. Therefor fields produce less garbage than methods.
*
* A Probe can be placed on field 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.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. By default the name of the field or method is used.
*
* @return the name of the Probe.
*/
String name() default "";
/**
* 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;
}