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/**
* Copyright 2017 VMware, Inc.
*
* 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
*
* https://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 io.micrometer.core.instrument;
import io.micrometer.core.lang.Nullable;
import java.util.Collections;
import java.util.function.ToDoubleFunction;
/**
* A counter that tracks a monotonically increasing function.
*
* @author Jon Schneider
*/
public interface FunctionCounter extends Meter {
static Builder builder(String name, @Nullable T obj, ToDoubleFunction f) {
return new Builder<>(name, obj, f);
}
/**
* @return The cumulative count since this counter was created.
*/
double count();
@Override
default Iterable measure() {
return Collections.singletonList(new Measurement(this::count, Statistic.COUNT));
}
/**
* Fluent builder for function counters.
*
* @param The type of the state object from which the counter value is extracted.
*/
class Builder {
private final String name;
private final ToDoubleFunction f;
private Tags tags = Tags.empty();
@Nullable
private final T obj;
@Nullable
private String description;
@Nullable
private String baseUnit;
private Builder(String name, @Nullable T obj, ToDoubleFunction f) {
this.name = name;
this.obj = obj;
this.f = f;
}
/**
* @param tags Must be an even number of arguments representing key/value pairs of tags.
* @return The function counter builder with added tags.
*/
public Builder tags(String... tags) {
return tags(Tags.of(tags));
}
/**
* @param tags Tags to add to the eventual function counter.
* @return The function counter builder with added tags.
*/
public Builder tags(Iterable tags) {
this.tags = this.tags.and(tags);
return this;
}
/**
* @param key The tag key.
* @param value The tag value.
* @return The function counter builder with a single added tag.
*/
public Builder tag(String key, String value) {
this.tags = tags.and(key, value);
return this;
}
/**
* @param description Description text of the eventual function counter.
* @return The function counter builder with added description.
*/
public Builder description(@Nullable String description) {
this.description = description;
return this;
}
/**
* @param unit Base unit of the eventual counter.
* @return The counter builder with added base unit.
*/
public Builder baseUnit(@Nullable String unit) {
this.baseUnit = unit;
return this;
}
/**
* Add the function counter to a single registry, or return an existing function counter in that registry. The returned
* function counter will be unique for each registry, but each registry is guaranteed to only create one function counter
* for the same combination of name and tags.
*
* @param registry A registry to add the function counter to, if it doesn't already exist.
* @return A new or existing function counter.
*/
public FunctionCounter register(MeterRegistry registry) {
return registry.more().counter(new Meter.Id(name, tags, baseUnit, description, Type.COUNTER), obj, f);
}
}
}