001/*
002 * Licensed to the Apache Software Foundation (ASF) under one or more
003 * contributor license agreements.  See the NOTICE file distributed with
004 * this work for additional information regarding copyright ownership.
005 * The ASF licenses this file to You under the Apache License, Version 2.0
006 * (the "License"); you may not use this file except in compliance with
007 * the License.  You may obtain a copy of the License at
008 *
009 *      http://www.apache.org/licenses/LICENSE-2.0
010 *
011 * Unless required by applicable law or agreed to in writing, software
012 * distributed under the License is distributed on an "AS IS" BASIS,
013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014 * See the License for the specific language governing permissions and
015 * limitations under the License.
016 */
017package org.apache.juneau.rest.server.metrics.micrometer;
018
019import org.apache.juneau.http.response.*;
020import org.apache.juneau.rest.server.*;
021import org.apache.juneau.rest.server.servlet.*;
022
023/**
024 * Child-resource flavor of the {@code /metrics} endpoint.
025 *
026 * <p>
027 * Mounts as a routed child via {@link Rest#children() @Rest(children=MetricsResource.class)} under the
028 * subtree {@code /metrics} and delegates to a shared {@link MetricsManager} worker &mdash; the same logic
029 * the {@link MetricsMixin mixin} flavor uses, so the two forms cannot drift.  Degrades to HTTP 501 when no
030 * scrapeable registry bean is present.
031 *
032 * <h5 class='section'>See Also:</h5><ul>
033 *    <li class='jc'>{@link MetricsMixin}
034 *    <li class='jc'>{@link MetricsManager}
035 * </ul>
036 *
037 * @since 10.0.0
038 */
039@Rest(path="/metrics")
040public class MetricsResource extends BasicRestResource {
041
042   private final MetricsManager manager = new MetricsManager();
043
044   /**
045    * [GET /] - Prometheus scrape of the consumer-provided MeterRegistry.
046    *
047    * @param req The HTTP request.
048    * @return The Prometheus exposition text.
049    * @throws NotImplemented If no scrapeable {@link io.micrometer.core.instrument.MeterRegistry} bean is registered.
050    */
051   @RestGet(
052      path="/*",
053      summary="Metrics scrape",
054      description="Renders a Prometheus text scrape from a consumer-provided Micrometer MeterRegistry bean."
055   )
056   public String getMetrics(RestRequest req) {
057      // A routed child's bean store inherits from its parent, so the consumer's MeterRegistry bean is
058      // reachable via this context's bean store.
059      var registry = manager.resolveRegistry(req.getContext());
060      var scrape = manager.scrape(registry);
061      if (scrape == null)
062         throw new NotImplemented("No scrapeable MeterRegistry is registered (a PrometheusMeterRegistry bean is required).");
063      return scrape;
064   }
065}