RetryMetrics.java

package io.github.resilience4j.metrics;

import com.codahale.metrics.*;
import io.github.resilience4j.retry.Retry;
import io.github.resilience4j.retry.RetryRegistry;
import io.vavr.collection.Array;

import java.util.Map;

import static com.codahale.metrics.MetricRegistry.name;
import static java.util.Objects.requireNonNull;

/**
 * An adapter which exports {@link Retry.Metrics} as Dropwizard Metrics Gauges.
 */
public class RetryMetrics implements MetricSet {

    private final MetricRegistry metricRegistry = new MetricRegistry();
    private static final String DEFAULT_PREFIX = "resilience4j.retry";

    private RetryMetrics(Iterable<Retry> retries){
        this(DEFAULT_PREFIX, retries);
    }

    private RetryMetrics(String prefix, Iterable<Retry> retries){
        requireNonNull(prefix);
        requireNonNull(retries);
        retries.forEach(retry -> {
            String name = retry.getName();
            Retry.Metrics metrics = retry.getMetrics();

            metricRegistry.register(name(prefix, name, "retry_max_ratio"),
                    new RetryRatio(metrics.getNumAttempts(), metrics.getMaxAttempts()));
            
        });
    }

    public static RetryMetrics ofRetryRegistry(String prefix, RetryRegistry retryRegistry) {
        return new RetryMetrics(prefix, retryRegistry.getAllRetries());
    }

    public static RetryMetrics ofRetryRegistry(RetryRegistry retryRegistry) {
        return new RetryMetrics(retryRegistry.getAllRetries());
    }

    public static RetryMetrics ofIterable(String prefix, Iterable<Retry> retries) {
        return new RetryMetrics(prefix, retries);
    }

    public static RetryMetrics ofIterable(Iterable<Retry> retries) {
        return new RetryMetrics(retries);
    }

    public static RetryMetrics ofRateLimiter(Retry retry) {
        return new RetryMetrics(Array.of(retry));
    }

    @Override
    public Map<String, Metric> getMetrics() {
        return metricRegistry.getMetrics();
    }

    /**
     * Implements a {@link RatioGauge} that represents the ratio between attempts made, and the maximum allowed retry attempts.
     */
    private final class RetryRatio extends RatioGauge {

        private double numAttempts;

        private double maxAttempts;

        public RetryRatio(int numAttempts, int maxAttempts) {
            this.numAttempts = (double) numAttempts;
            this.maxAttempts = (double) maxAttempts;
        }

        @Override
        protected Ratio getRatio() {
            return Ratio.of(numAttempts, maxAttempts);
        }
    }
}