io.helidon.metrics.prometheus.PrometheusSupport Maven / Gradle / Ivy
/*
* Copyright (c) 2017, 2023 Oracle and/or its affiliates.
*
* 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
*
* http://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 io.helidon.metrics.prometheus;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.List;
import java.util.Optional;
import java.util.Set;
import io.helidon.http.HttpMediaType;
import io.helidon.webserver.http.HttpRouting;
import io.helidon.webserver.http.HttpRules;
import io.helidon.webserver.http.HttpService;
import io.helidon.webserver.http.ServerRequest;
import io.helidon.webserver.http.ServerResponse;
import io.helidon.webserver.servicecommon.HelidonFeatureSupport;
import io.prometheus.client.Collector;
import io.prometheus.client.CollectorRegistry;
/**
* Support for Prometheus client endpoint.
*
* Default and simplest use on {@link HttpRouting} creates {@code /metrics} endpoint
* for {@link CollectorRegistry default CollectorRegistry}.
*
{@code
* HttpRouting.builder()
* ..addFeature(PrometheusSupport.create())
* }
*/
public final class PrometheusSupport extends HelidonFeatureSupport {
private static final System.Logger LOGGER = System.getLogger(PrometheusSupport.class.getName());
/**
* Standard path of Prometheus client resource: {@code /metrics}.
*/
private static final String DEFAULT_PATH = "/metrics";
private static final HttpMediaType CONTENT_TYPE = HttpMediaType.create("text/plain; version=0.0.4; charset=utf-8");
private final CollectorRegistry collectorRegistry;
private final String path;
private PrometheusSupport(Builder builder) {
super(LOGGER, builder, "prometheus");
this.collectorRegistry = builder.registry;
this.path = builder.path;
}
private void configureRoutes(HttpRules rules) {
rules.get(path, this::process);
}
@Override
public Optional service() {
return Optional.of(this::configureRoutes);
}
private void process(ServerRequest req, ServerResponse res) {
// Recent releases of the Prometheus client append suffixes such as "_total" to the meter names. To preserve the
// outward behavior of this endpoint where the query parameter specifies the base name (without the suffix),
// pass a predicate for filtering rather than just the set of strings of base names.
Set filters = new HashSet<>(req.query().all("name[]", List::of));
Enumeration mfs = collectorRegistry.filteredMetricFamilySamples(candidate ->
filters.isEmpty() || filters.stream().anyMatch(candidate::startsWith));
res.headers().contentType(CONTENT_TYPE);
res.send(compose(mfs));
}
/**
* Compose the text version 0.0.4 of the given MetricFamilySamples.
*/
private static String compose(Enumeration mfs) {
/* See http://prometheus.io/docs/instrumenting/exposition_formats/
* for the output format specification. */
StringBuilder result = new StringBuilder();
while (mfs.hasMoreElements()) {
Collector.MetricFamilySamples metricFamilySamples = mfs.nextElement();
result.append("# HELP ")
.append(metricFamilySamples.name)
.append(' ');
appendEscapedHelp(result, metricFamilySamples.help);
result.append('\n');
result.append("# TYPE ")
.append(metricFamilySamples.name)
.append(' ')
.append(typeString(metricFamilySamples.type))
.append('\n');
for (Collector.MetricFamilySamples.Sample sample: metricFamilySamples.samples) {
result.append(sample.name);
if (!sample.labelNames.isEmpty()) {
result.append('{');
for (int i = 0; i < sample.labelNames.size(); ++i) {
result.append(sample.labelNames.get(i))
.append("=\"");
appendEscapedLabelValue(result, sample.labelValues.get(i));
result.append("\",");
}
result.append('}');
}
result.append(' ')
.append(Collector.doubleToGoString(sample.value))
.append('\n');
}
}
return result.toString();
}
private static void appendEscapedHelp(StringBuilder sb, String s) {
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
switch (c) {
case '\\':
sb.append("\\\\");
break;
case '\n':
sb.append("\\n");
break;
default:
sb.append(c);
}
}
}
private static void appendEscapedLabelValue(StringBuilder sb, String s) {
for (int i = 0; i < s.length(); i++) {
char c = s.charAt(i);
switch (c) {
case '\\':
sb.append("\\\\");
break;
case '\"':
sb.append("\\\"");
break;
case '\n':
sb.append("\\n");
break;
default:
sb.append(c);
}
}
}
private static String typeString(Collector.Type t) {
switch (t) {
case GAUGE:
return "gauge";
case COUNTER:
return "counter";
case SUMMARY:
return "summary";
case HISTOGRAM:
return "histogram";
default:
return "untyped";
}
}
/**
* Creates new instance using specified Prometheus {@link CollectorRegistry}.
*
* @param collectorRegistry a registry to use
* @return new instance
* @see #create()
* @see #builder()
*/
public static PrometheusSupport create(CollectorRegistry collectorRegistry) {
return builder().collectorRegistry(collectorRegistry).build();
}
/**
* Creates new instance using default Prometheus {@link CollectorRegistry}.
*
* @return new instance
* @see CollectorRegistry
* @see #create(CollectorRegistry)
* @see #builder()
*/
public static PrometheusSupport create() {
return builder().build();
}
/**
* Creates new {@code Builder} instance.
*
* @return the new instance
* @see #create()
* @see #create(CollectorRegistry)
*/
public static Builder builder() {
return new Builder();
}
/**
* A builder of {@link PrometheusSupport}.
*/
public static final class Builder extends HelidonFeatureSupport.Builder {
private CollectorRegistry registry = CollectorRegistry.defaultRegistry;
private String path = DEFAULT_PATH;
private Builder() {
super("/");
}
/**
* Sets collector registry to use, default is {@link CollectorRegistry#defaultRegistry}.
*
* @param registry a registry to use
* @return updated builder
*/
public Builder collectorRegistry(CollectorRegistry registry) {
this.registry = registry;
return this;
}
/**
* Sets path of the metrics resource, default is {@code /metrics}.
*
* @param path a resource path
* @return updated builder
*/
public Builder path(String path) {
if (path == null || path.isEmpty()) {
this.path = "/";
} else {
this.path = path;
}
return this;
}
@Override
public PrometheusSupport build() {
return new PrometheusSupport(this);
}
}
}
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