fish.payara.microprofile.metrics.cdi.MetricUtils Maven / Gradle / Ivy

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package fish.payara.microprofile.metrics.cdi;

import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.atomic.AtomicReference;
import java.util.function.Supplier;

import org.eclipse.microprofile.metrics.ConcurrentGauge;
import org.eclipse.microprofile.metrics.Counter;
import org.eclipse.microprofile.metrics.Gauge;
import org.eclipse.microprofile.metrics.Histogram;
import org.eclipse.microprofile.metrics.Metadata;
import org.eclipse.microprofile.metrics.Meter;
import org.eclipse.microprofile.metrics.Metric;
import org.eclipse.microprofile.metrics.MetricID;
import org.eclipse.microprofile.metrics.MetricRegistry;
import org.eclipse.microprofile.metrics.SimpleTimer;
import org.eclipse.microprofile.metrics.Tag;
import org.eclipse.microprofile.metrics.Timer;

/**
 * Unfortunately the {@link MetricRegistry} has no generic versions of the get or register methods for the different
 * types of {@link Metric}s. Therefore this utility provides a generic API by mapping the generic methods to the type
 * specific ones.
 *
 * @author Jan Bernitt
 * @since 5.202
 */
public final class MetricUtils {

    @FunctionalInterface
    private interface By {

        R apply(MetricRegistry registry, A a, B b);
    }

    @FunctionalInterface
    private interface ByJust {

        R apply(MetricRegistry registry, A a);
    }

    private static final Map, MetricUtils> TYPES = new HashMap<>();

    private final ByJust byName;
    private final By byNameAndTags;
    private final By byMetadataAndTags;

    private MetricUtils(
            ByJust byName,
            By byNameAndTags,
            By byMetadataAndTags) {
        this.byName = byName;
        this.byNameAndTags = byNameAndTags;
        this.byMetadataAndTags = byMetadataAndTags;
    }

    static  void register(
            Class type, ByJust byName,
            By byNameAndTags,
            By byMetadataAndTags) {
        TYPES.put(type, new MetricUtils<>(byName, byNameAndTags, byMetadataAndTags));
    }

    static {
        register(Counter.class, MetricRegistry::counter, MetricRegistry::counter, MetricRegistry::counter);
        register(ConcurrentGauge.class, MetricRegistry::concurrentGauge, MetricRegistry::concurrentGauge, MetricRegistry::concurrentGauge);
        register(Histogram.class, MetricRegistry::histogram, MetricRegistry::histogram, MetricRegistry::histogram);
        register(Meter.class, MetricRegistry::meter, MetricRegistry::meter, MetricRegistry::meter);
        register(Timer.class, MetricRegistry::timer, MetricRegistry::timer, MetricRegistry::timer);
        register(SimpleTimer.class, MetricRegistry::simpleTimer, MetricRegistry::simpleTimer, MetricRegistry::simpleTimer);
        register(Gauge.class, MetricUtils::getGauge, MetricUtils::getGauge, MetricUtils::getGauge);
    }

    @SuppressWarnings("unchecked")
    public static  T getOrRegisterByName(MetricRegistry registry, Class metric, String name) {
        return (T) getOrRegister(metric).byName.apply(registry, name);
    }

    @SuppressWarnings("unchecked")
    public static  T getOrRegisterByNameAndTags(MetricRegistry registry, Class metric, String name,
            Tag... tags) {
        return (T) getOrRegister(metric).byNameAndTags.apply(registry, name, tags);
    }

    @SuppressWarnings("unchecked")
    public static  T getOrRegisterByMetadataAndTags(MetricRegistry registry, Class metric,
            Metadata metadata, Tag... tags) {
        return (T) getOrRegister(metric).byMetadataAndTags.apply(registry, metadata, tags);
    }

    private static  MetricUtils getOrRegister(Class metric) {
        MetricUtils getOrRegister = TYPES.get(metric);
        if (getOrRegister == null) {
            throw new IllegalArgumentException("Cannot get or register metrics of type " + metric);
        }
        return getOrRegister;
    }

    /*
     * Gauges can only be resolved as registering requires the actual gauge instance.
     */

    private static Gauge getGauge(MetricRegistry registry, String name) {
        return getGauge(registry, name, new Tag[0]);
    }

    private static Gauge getGauge(MetricRegistry registry, Metadata metadata, Tag[] tags) {
        return getGauge(registry, metadata.getName(), tags);
    }

    @SuppressWarnings("unchecked")
    private static Gauge getGauge(MetricRegistry registry, String name, Tag[] tags) {
        MetricID metricID = new MetricID(name, tags);
        Gauge gauge = registry.getGauges().get(metricID);
        return gauge != null ? gauge : new LazyGauge<>(() -> registry.getGauges().get(metricID));
    }

    private static final class LazyGauge implements Gauge {

        private final AtomicReference> gauge = new AtomicReference<>();
        private final Supplier> lookup;
        LazyGauge(Supplier> lookup) {
            this.lookup = lookup;
        }
        @Override
        public T getValue() {
            Gauge lazy = gauge.updateAndGet(instance -> instance != null ? instance : lookup.get());
            return lazy == null ? null : lazy.getValue();
        }


    }
}