/
PrometheusScrapeEndpoint.java
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/
PrometheusScrapeEndpoint.java
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/*
* Copyright 2012-2021 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.boot.actuate.metrics.export.prometheus;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Enumeration;
import java.util.Set;
import io.prometheus.client.Collector.MetricFamilySamples;
import io.prometheus.client.CollectorRegistry;
import org.springframework.boot.actuate.endpoint.annotation.Endpoint;
import org.springframework.boot.actuate.endpoint.annotation.ReadOperation;
import org.springframework.boot.actuate.endpoint.web.WebEndpointResponse;
import org.springframework.boot.actuate.endpoint.web.annotation.WebEndpoint;
import org.springframework.lang.Nullable;
/**
* {@link Endpoint @Endpoint} that outputs metrics in a format that can be scraped by the
* Prometheus server.
*
* @author Jon Schneider
* @author Johnny Lim
* @since 2.0.0
*/
@WebEndpoint(id = "prometheus")
public class PrometheusScrapeEndpoint {
private static final int METRICS_SCRAPE_CHARS_EXTRA = 1024;
private final CollectorRegistry collectorRegistry;
private volatile int nextMetricsScrapeSize = 16;
public PrometheusScrapeEndpoint(CollectorRegistry collectorRegistry) {
this.collectorRegistry = collectorRegistry;
}
@ReadOperation(producesFrom = TextOutputFormat.class)
public WebEndpointResponse<String> scrape(TextOutputFormat format, @Nullable Set<String> includedNames) {
try {
Writer writer = new StringWriter(this.nextMetricsScrapeSize);
Enumeration<MetricFamilySamples> samples = (includedNames != null)
? this.collectorRegistry.filteredMetricFamilySamples(includedNames)
: this.collectorRegistry.metricFamilySamples();
format.write(writer, samples);
String scrapePage = writer.toString();
this.nextMetricsScrapeSize = scrapePage.length() + METRICS_SCRAPE_CHARS_EXTRA;
return new WebEndpointResponse<>(scrapePage, format);
}
catch (IOException ex) {
// This actually never happens since StringWriter doesn't throw an IOException
throw new IllegalStateException("Writing metrics failed", ex);
}
}
}