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• 4.1.3
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• NoOpMeterRegistry.java

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io.helidon.metrics.api.NoOpMeterRegistry Maven / Gradle / Ivy

/*
 * Copyright (c) 2023 Oracle and/or its affiliates.
 *
 * 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 io.helidon.metrics.api;

import java.util.Collection;
import java.util.List;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.function.Consumer;
import java.util.function.Predicate;

/**
 * No-op implementation of {@link io.helidon.metrics.api.MeterRegistry}.
 * 

 * Note that the no-op meter registry implementation does not actually
 * store meters or their IDs, in line with the documented behavior of disabled metrics.
 * 
 */
class NoOpMeterRegistry implements MeterRegistry, NoOpWrapper {

    private final List> onAddListeners = new CopyOnWriteArrayList<>();
    private final List> onRemoveListeners = new CopyOnWriteArrayList<>();

    static Builder builder() {
        return new Builder();
    }

    @Override
    public void close() {
    }

    @Override
    public List meters() {
        return List.of();
    }

    @Override
    public Collection meters(Predicate filter) {
        return Set.of();
    }

    @Override
    public Iterable meters(Iterable scopeSelection) {
        return Set.of();
    }

    @Override
    public Clock clock() {
        return Clock.system();
    }

    @Override
    public Optional remove(Meter.Id id) {
        return Optional.empty();
    }

    @Override
    public Optional remove(Meter meter) {
        onRemoveListeners.forEach(listener -> listener.accept(meter));
        return Optional.empty();
    }

    @Override
    public Optional remove(String name, Iterable tags) {
        return Optional.empty();
    }

    @Override
    public Optional remove(Meter.Id id, String scope) {
        return Optional.empty();
    }

    @Override
    public Optional remove(String name, Iterable tags, String scope) {
        return Optional.empty();
    }

    @Override
    public  Optional meter(Class mClass, String name, Iterable tags) {
        return Optional.empty();
    }

    @Override
    public boolean isDeleted(Meter meter) {
        return false;
    }

    @Override
    public boolean isMeterEnabled(String name, Map tags, Optional scope) {
        return true;
    }

    @Override
    public Iterable scopes() {
        return Set.of();
    }

    @Override
    public , M extends Meter> M getOrCreate(B builder) {
        NoOpMeter.Builder b = (NoOpMeter.Builder) builder;
        M result = findOrRegister(NoOpMeter.Id.create(b.name(),
                                                      b.tags()),
                                  builder);
        onAddListeners.forEach(listener -> listener.accept(result));
        return result;
    }

    @Override
    public MeterRegistry onMeterAdded(Consumer listener) {
        onAddListeners.add(listener);
        return this;
    }

    @Override
    public MeterRegistry onMeterRemoved(Consumer listener) {
        onRemoveListeners.add(listener);
        return this;
    }

    private  Optional find(Meter.Id id, Class mClass) {
        return Optional.empty();
    }

    private > M findOrRegister(Meter.Id id, B builder) {
        NoOpMeter.Builder noOpBuilder = (NoOpMeter.Builder) builder;
        // The following cast will always succeed if we create the meter by invoking the builder,
        // it will succeed if we retrieved a previously-registered meter of a compatible type,
        // and it will (correctly) fail if we found a previously-registered meter of an incompatible
        // type compared to what the caller requested.
        return (M) noOpBuilder.build();
    }

    static class Builder implements MeterRegistry.Builder {

        @Override
        public NoOpMeterRegistry build() {
            return new NoOpMeterRegistry();
        }

        @Override
        public Builder clock(Clock clock) {
            return identity();
        }

        @Override
        public Builder metricsConfig(MetricsConfig metricsConfig) {
            return identity();
        }

        @Override
        public Builder onMeterAdded(Consumer addListener) {
            return identity();
        }

        @Override
        public Builder onMeterRemoved(Consumer removeListener) {
            return identity();
        }
    }
}