PoolGaugesDemo.java

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package org.apache.hc.client5.http.observation.example;

import java.net.URI;
import java.util.EnumSet;

import io.micrometer.core.instrument.Metrics;
import io.micrometer.core.instrument.search.Search;
import io.micrometer.observation.ObservationRegistry;
import io.micrometer.prometheusmetrics.PrometheusConfig;
import io.micrometer.prometheusmetrics.PrometheusMeterRegistry;
import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;
import org.apache.hc.client5.http.impl.classic.HttpClientBuilder;
import org.apache.hc.client5.http.impl.classic.HttpClients;
import org.apache.hc.client5.http.impl.io.PoolingHttpClientConnectionManager;
import org.apache.hc.client5.http.io.HttpClientConnectionManager;
import org.apache.hc.client5.http.observation.HttpClientObservationSupport;
import org.apache.hc.client5.http.observation.MetricConfig;
import org.apache.hc.client5.http.observation.ObservingOptions;
import org.apache.hc.core5.http.ClassicHttpResponse;
import org.apache.hc.core5.http.io.support.ClassicRequestBuilder;

public final class PoolGaugesDemo {

    private static final URI URL = URI.create("https://httpbin.org/get");

    public static void main(final String[] args) throws Exception {
        final PrometheusMeterRegistry reg = new PrometheusMeterRegistry(PrometheusConfig.DEFAULT);
        Metrics.addRegistry(reg);

        final ObservationRegistry obs = ObservationRegistry.create();

        final MetricConfig mc = MetricConfig.builder().build();
        final ObservingOptions opts = ObservingOptions.builder()
                .metrics(EnumSet.of(ObservingOptions.MetricSet.BASIC,
                        ObservingOptions.MetricSet.CONN_POOL))
                .tagLevel(ObservingOptions.TagLevel.LOW)
                .build();

        // Ensure a pooling manager is used so pool gauges exist
        final HttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
        final HttpClientBuilder b = HttpClients.custom().setConnectionManager(cm);

        HttpClientObservationSupport.enable(b, obs, reg, opts, mc);

        try (final CloseableHttpClient client = b.build()) {
            final ClassicHttpResponse rsp = client.executeOpen(null, ClassicRequestBuilder.get(URL).build(), null);
            rsp.close();
        }

        System.out.println("pool.leased    present? " + (Search.in(reg).name("http.client.pool.leased").gauge() != null));
        System.out.println("pool.available present? " + (Search.in(reg).name("http.client.pool.available").gauge() != null));
        System.out.println("pool.pending   present? " + (Search.in(reg).name("http.client.pool.pending").gauge() != null));

        System.out.println("--- scrape ---");
        System.out.println(reg.scrape());
    }

    private PoolGaugesDemo() {
    }
}