001/*
002 * Copyright 2012-2018 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.boot.actuate.metrics.export.prometheus;
018
019import java.io.IOException;
020import java.io.StringWriter;
021import java.io.Writer;
022
023import io.prometheus.client.CollectorRegistry;
024import io.prometheus.client.exporter.common.TextFormat;
025
026import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
027import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
028import org.springframework.boot.actuate.endpoint.web.annotation.WebEndpoint;
029
030/**
031 * {@link Endpoint} that outputs metrics in a format that can be scraped by the Prometheus
032 * server.
033 *
034 * @author Jon Schneider
035 * @since 2.0.0
036 */
037@WebEndpoint(id = "prometheus")
038public class PrometheusScrapeEndpoint {
039
040        private final CollectorRegistry collectorRegistry;
041
042        public PrometheusScrapeEndpoint(CollectorRegistry collectorRegistry) {
043                this.collectorRegistry = collectorRegistry;
044        }
045
046        @ReadOperation(produces = TextFormat.CONTENT_TYPE_004)
047        public String scrape() {
048                try {
049                        Writer writer = new StringWriter();
050                        TextFormat.write004(writer, this.collectorRegistry.metricFamilySamples());
051                        return writer.toString();
052                }
053                catch (IOException ex) {
054                        // This actually never happens since StringWriter::write() doesn't throw any
055                        // IOException
056                        throw new RuntimeException("Writing metrics failed", ex);
057                }
058        }
059
060}