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Add a Httpserver (#276)
* Copy over key bit of PR#73 for HttpServer exposition. #73 by tgulacsi * Cleanup httpserver, allow mutliple simultaneous requests. * Support specifying host. * Add support for ?name[]=
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‎README.md‎

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@@ -515,9 +515,14 @@ There are several options for exporting metrics.
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Metrics are usually exposed over HTTP, to be read by the Prometheus server.
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There are Servlet, SpringBoot, and Vert.x integrations included in the client library.
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There are HTTPServer, Servlet, SpringBoot, and Vert.x integrations included in the client library.
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The simplest of these is the HTTPServer:
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To add Prometheus exposition to an existing HTTP server, see the `MetricsServlet`.
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```java
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HTTPServer server = new HTTPServer(1234);
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```
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To add Prometheus exposition to an existing HTTP server using servlets, see the `MetricsServlet`.
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It also serves as a simple example of how to write a custom endpoint.
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To expose the metrics used in your code, you would add the Prometheus servlet to your Jetty server:
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context.addServlet(new ServletHolder(new MetricsServlet()), "/metrics");
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```
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All HTTP expostion integrations support restricting which time series to return
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using `?name[]=` URL parameters. Due to implementation limitations, this may
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have false negatives.
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## Exporting to a Pushgateway

‎pom.xml‎

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<module>simpleclient_hibernate</module>
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<module>simpleclient_guava</module>
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<module>simpleclient_hotspot</module>
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<module>simpleclient_httpserver</module>
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<module>simpleclient_log4j</module>
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<module>simpleclient_log4j2</module>
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<module>simpleclient_logback</module>

‎simpleclient_httpserver/pom.xml‎

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<parent>
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<groupId>io.prometheus</groupId>
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<artifactId>parent</artifactId>
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<version>0.0.24-SNAPSHOT</version>
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</parent>
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<groupId>io.prometheus</groupId>
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<artifactId>simpleclient_httpserver</artifactId>
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<packaging>bundle</packaging>
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<name>Prometheus Java Simpleclient Httpserver</name>
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<description>
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Httpserver exposition for the simpleclient.
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</description>
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<licenses>
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<license>
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<name>The Apache Software License, Version 2.0</name>
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<url>http://www.apache.org/licenses/LICENSE-2.0.txt</url>
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<distribution>repo</distribution>
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</license>
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</licenses>
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<developers>
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<developer>
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<id>brian-brazil</id>
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<name>Brian Brazil</name>
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<email>[email protected]</email>
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</developer>
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</developers>
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<dependencies>
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<dependency>
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<groupId>io.prometheus</groupId>
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<artifactId>simpleclient</artifactId>
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<version>0.0.24-SNAPSHOT</version>
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</dependency>
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<dependency>
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<groupId>io.prometheus</groupId>
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<artifactId>simpleclient_common</artifactId>
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<version>0.0.24-SNAPSHOT</version>
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</dependency>
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<!-- Test Dependencies Follow -->
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<dependency>
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<groupId>junit</groupId>
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<artifactId>junit</artifactId>
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<version>4.11</version>
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<scope>test</scope>
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</dependency>
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<dependency>
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<groupId>org.assertj</groupId>
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<artifactId>assertj-core</artifactId>
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<version>2.6.0</version>
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<scope>test</scope>
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</dependency>
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</dependencies>
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</project>

‎simpleclient_httpserver/src/main/java/io/prometheus/client/exporter/HTTPServer.java‎

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package io.prometheus.client.exporter;
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import io.prometheus.client.CollectorRegistry;
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import io.prometheus.client.exporter.common.TextFormat;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.io.OutputStreamWriter;
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import java.net.InetSocketAddress;
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import java.net.URLDecoder;
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import java.util.Set;
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import java.util.HashSet;
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import java.util.concurrent.Executors;
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import com.sun.net.httpserver.HttpHandler;
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import com.sun.net.httpserver.HttpServer;
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import com.sun.net.httpserver.HttpExchange;
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/**
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* Expose Prometheus metrics using a plain Java HttpServer.
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* <p>
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* Example Usage:
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* <pre>
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* {@code
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* HTTPServer server = new HTTPServer(1234);
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* }
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* </pre>
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* */
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public class HTTPServer {
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static class HTTPMetricHandler implements HttpHandler {
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private CollectorRegistry registry;
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HTTPMetricHandler(CollectorRegistry registry) {
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this.registry = registry;
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}
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public void handle(HttpExchange t) throws IOException {
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String query = t.getRequestURI().getRawQuery();
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ByteArrayOutputStream response = new ByteArrayOutputStream(1 << 20);
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OutputStreamWriter osw = new OutputStreamWriter(response);
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TextFormat.write004(osw,
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registry.filteredMetricFamilySamples(parseQuery(query)));
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osw.flush();
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osw.close();
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response.flush();
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response.close();
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t.getResponseHeaders().set("Content-Type",
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TextFormat.CONTENT_TYPE_004);
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t.getResponseHeaders().set("Content-Length",
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String.valueOf(response.size()));
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t.sendResponseHeaders(200, response.size());
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response.writeTo(t.getResponseBody());
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t.close();
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}
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}
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protected static Set<String> parseQuery(String query) throws IOException {
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Set<String> names = new HashSet<String>();
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if (query != null) {
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String[] pairs = query.split("&");
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for (String pair : pairs) {
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int idx = pair.indexOf("=");
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if (idx != -1 && URLDecoder.decode(pair.substring(0, idx), "UTF-8").equals("name[]")) {
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names.add(URLDecoder.decode(pair.substring(idx + 1), "UTF-8"));
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}
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}
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}
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return names;
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}
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protected HttpServer server;
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/**
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* Start a HTTP server serving Prometheus metrics from the given registry.
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*/
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public HTTPServer(InetSocketAddress addr, CollectorRegistry registry) throws IOException {
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server = HttpServer.create();
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server.bind(addr, 3);
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HttpHandler mHandler = new HTTPMetricHandler(registry);
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server.createContext("/", mHandler);
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server.createContext("/metrics", mHandler);
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server.setExecutor(Executors.newFixedThreadPool(5));
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server.start();
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}
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/**
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* Start a HTTP server serving the default Prometheus registry.
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*/
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public HTTPServer(int port) throws IOException {
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this(new InetSocketAddress(port), CollectorRegistry.defaultRegistry);
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}
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/**
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* Start a HTTP server serving the default Prometheus registry.
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*/
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public HTTPServer(String host, int port) throws IOException {
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this(new InetSocketAddress(host, port), CollectorRegistry.defaultRegistry);
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}
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/**
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* Stop the HTTP server.
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*/
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public void stop() {
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server.stop(0);
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}
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}
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‎simpleclient_httpserver/src/test/java/io/prometheus/client/exporter/ExampleExporter.java‎

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package io.prometheus.client.exporter;
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import io.prometheus.client.Counter;
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import io.prometheus.client.Gauge;
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import io.prometheus.client.Histogram;
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import io.prometheus.client.Summary;
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public class ExampleExporter {
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static final Gauge g = Gauge.build().name("gauge").help("blah").register();
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static final Counter c = Counter.build().name("counter").help("meh").register();
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static final Summary s = Summary.build().name("summary").help("meh").register();
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static final Histogram h = Histogram.build().name("histogram").help("meh").register();
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static final Gauge l = Gauge.build().name("labels").help("blah").labelNames("l").register();
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public static void main(String[] args) throws Exception {
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new HTTPServer(1234);
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g.set(1);
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c.inc(2);
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s.observe(3);
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h.observe(4);
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l.labels("foo").inc(5);
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}
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}

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