feat: Add metricsHandlerPath and registerHealthHandler configuration options to HTTPServer

Donnerbart · Donnerbart · commit 2d8cf2070322 · 2025-12-18T14:37:15.000+01:00
Signed-off-by: David Sondermann &lt;david.sondermann@hivemq.com&gt;
diff --git a/prometheus-metrics-exporter-httpserver/src/main/java/io/prometheus/metrics/exporter/httpserver/DefaultHandler.java b/prometheus-metrics-exporter-httpserver/src/main/java/io/prometheus/metrics/exporter/httpserver/DefaultHandler.java
@@ -11,24 +11,27 @@ public class DefaultHandler implements HttpHandler {
   private final byte[] responseBytes;
   private final String contentType;
 
-  public DefaultHandler() {
+  public DefaultHandler(String metricsPath) {
+    String metrics = metricsPath.startsWith("/") ? metricsPath.substring(1) : metricsPath;
     String responseString =
         "<html>\n"
             + "<head><title>Prometheus Java Client</title></head>\n"
             + "<body>\n"
             + "<h1>Prometheus Java Client</h1>\n"
             + "<h2>Metrics Path</h2>\n"
-            + "The metrics path is <a href=\"metrics\">/metrics</a>.\n"
+            + String.format("The metrics path is <a href=\"%s\">%s</a>.\n", metrics, metricsPath)
             + "<h2>Name Filter</h2>\n"
             + "If you want to scrape only specific metrics, "
             + "use the <tt>name[]</tt> parameter like this:\n"
             + "<ul>\n"
-            + "<li><a href=\"metrics?name[]=my_metric\">/metrics?name[]=my_metric</a></li>\n"
+            + String.format(
+                "<li><a href=\"%s?name[]=my_metric\">%s?name[]=my_metric</a></li>\n",
+                metrics, metricsPath)
             + "</ul>\n"
             + "You can also use multiple <tt>name[]</tt> parameters to query multiple metrics:\n"
             + "<ul>\n"
-            + "<li><a href=\"metrics?name[]=my_metric_a&name=my_metrics_b\">"
-            + "/metrics?name[]=my_metric_a&amp;name=[]=my_metric_b</a></li>\n"
+            + String.format("<li><a href=\"%s?name[]=my_metric_a&name[]=my_metric_b\">", metrics)
+            + String.format("%s?name[]=my_metric_a&amp;name[]=my_metric_b</a></li>\n", metricsPath)
             + "</ul>\n"
             + "The <tt>name[]</tt> parameter can be used by the Prometheus server for scraping. "
             + "Add the following snippet to your scrape job configuration in "
@@ -50,13 +53,17 @@ public DefaultHandler() {
             + "The Prometheus Java metrics library supports a <tt>debug</tt> query parameter "
             + "for viewing the different formats in a Web browser:\n"
             + "<ul>\n"
-            + "<li><a href=\"metrics?debug=openmetrics\">/metrics?debug=openmetrics</a>: "
+            + String.format(
+                "<li><a href=\"%s?debug=openmetrics\">%s?debug=openmetrics</a>: ",
+                metrics, metricsPath)
             + "View OpenMetrics text format.</li>\n"
-            + "<li><a href=\"metrics?debug=text\">/metrics?debug=text</a>: "
+            + String.format(
+                "<li><a href=\"%s?debug=text\">%s?debug=text</a>: ", metrics, metricsPath)
             + "View Prometheus text format (this is the default when accessing the "
-            + "<a href=\"metrics\">/metrics</a> endpoint with a Web browser).</li>\n"
-            + "<li><a href=\"metrics?debug=prometheus-protobuf\">"
-            + "/metrics?debug=prometheus-protobuf</a>: "
+            + String.format(
+                "<a href=\"%s\">%s</a> endpoint with a Web browser).</li>\n", metrics, metricsPath)
+            + String.format("<li><a href=\"%s?debug=prometheus-protobuf\">", metrics)
+            + String.format("%s?debug=prometheus-protobuf</a>: ", metricsPath)
             + "View a text representation of the Prometheus protobuf format.</li>\n"
             + "</ul>\n"
             + "Note that the <tt>debug</tt> parameter is only for viewing different formats in a "
diff --git a/prometheus-metrics-exporter-httpserver/src/main/java/io/prometheus/metrics/exporter/httpserver/HTTPServer.java b/prometheus-metrics-exporter-httpserver/src/main/java/io/prometheus/metrics/exporter/httpserver/HTTPServer.java
@@ -1,12 +1,6 @@
 package io.prometheus.metrics.exporter.httpserver;
 
-import com.sun.net.httpserver.Authenticator;
-import com.sun.net.httpserver.HttpContext;
-import com.sun.net.httpserver.HttpExchange;
-import com.sun.net.httpserver.HttpHandler;
-import com.sun.net.httpserver.HttpServer;
-import com.sun.net.httpserver.HttpsConfigurator;
-import com.sun.net.httpserver.HttpsServer;
+import com.sun.net.httpserver.*;
 import io.prometheus.metrics.config.PrometheusProperties;
 import io.prometheus.metrics.model.registry.PrometheusRegistry;
 import java.io.Closeable;
@@ -16,11 +10,7 @@
 import java.net.InetSocketAddress;
 import java.security.PrivilegedActionException;
 import java.security.PrivilegedExceptionAction;
-import java.util.concurrent.ExecutionException;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.SynchronousQueue;
-import java.util.concurrent.ThreadPoolExecutor;
-import java.util.concurrent.TimeUnit;
+import java.util.concurrent.*;
 import javax.annotation.Nullable;
 import javax.security.auth.Subject;
 
@@ -57,24 +47,29 @@ private HTTPServer(
       PrometheusRegistry registry,
       @Nullable Authenticator authenticator,
       @Nullable String authenticatedSubjectAttributeName,
-      @Nullable HttpHandler defaultHandler) {
+      @Nullable HttpHandler defaultHandler,
+      @Nullable String metricsHandlerPath,
+      @Nullable Boolean registerHealthHandler) {
     if (httpServer.getAddress() == null) {
       throw new IllegalArgumentException("HttpServer hasn't been bound to an address");
     }
     this.server = httpServer;
     this.executorService = executorService;
+    String metricsPath = getMetricsPath(metricsHandlerPath);
     registerHandler(
         "/",
-        defaultHandler == null ? new DefaultHandler() : defaultHandler,
+        defaultHandler == null ? new DefaultHandler(metricsPath) : defaultHandler,
         authenticator,
         authenticatedSubjectAttributeName);
     registerHandler(
-        "/metrics",
+        metricsPath,
         new MetricsHandler(config, registry),
         authenticator,
         authenticatedSubjectAttributeName);
-    registerHandler(
-        "/-/healthy", new HealthyHandler(), authenticator, authenticatedSubjectAttributeName);
+    if (registerHealthHandler == null || registerHealthHandler) {
+      registerHandler(
+          "/-/healthy", new HealthyHandler(), authenticator, authenticatedSubjectAttributeName);
+    }
     try {
       // HttpServer.start() starts the HttpServer in a new background thread.
       // If we call HttpServer.start() from a thread of the executorService,
@@ -88,6 +83,16 @@ private HTTPServer(
     }
   }
 
+  private String getMetricsPath(@Nullable String metricsHandlerPath) {
+    if (metricsHandlerPath == null) {
+      return "/metrics";
+    }
+    if (!metricsHandlerPath.startsWith("/")) {
+      return "/" + metricsHandlerPath;
+    }
+    return metricsHandlerPath;
+  }
+
   private void registerHandler(
       String path,
       HttpHandler handler,
@@ -179,9 +184,11 @@ public static class Builder {
     @Nullable private ExecutorService executorService = null;
     @Nullable private PrometheusRegistry registry = null;
     @Nullable private Authenticator authenticator = null;
+    @Nullable private String authenticatedSubjectAttributeName = null;
     @Nullable private HttpsConfigurator httpsConfigurator = null;
     @Nullable private HttpHandler defaultHandler = null;
-    @Nullable private String authenticatedSubjectAttributeName = null;
+    @Nullable private String metricsHandlerPath = null;
+    @Nullable private Boolean registerHealthHandler = null;
 
     private Builder(PrometheusProperties config) {
       this.config = config;
@@ -254,6 +261,18 @@ public Builder defaultHandler(HttpHandler defaultHandler) {
       return this;
     }
 
+    /** Optional: Override default path for the metrics endpoint. Default is {@code /metrics}. */
+    public Builder metricsHandlerPath(String metricsHandlerPath) {
+      this.metricsHandlerPath = metricsHandlerPath;
+      return this;
+    }
+
+    /** Optional: Override if the health handler should be registered. Default is {@code true}. */
+    public Builder registerHealthHandler(boolean registerHealthHandler) {
+      this.registerHealthHandler = registerHealthHandler;
+      return this;
+    }
+
     /** Build and start the HTTPServer. */
     public HTTPServer buildAndStart() throws IOException {
       if (registry == null) {
@@ -275,7 +294,9 @@ public HTTPServer buildAndStart() throws IOException {
           registry,
           authenticator,
           authenticatedSubjectAttributeName,
-          defaultHandler);
+          defaultHandler,
+          metricsHandlerPath,
+          registerHealthHandler);
     }
 
     private InetSocketAddress makeInetSocketAddress() {
diff --git a/prometheus-metrics-exporter-httpserver/src/test/java/io/prometheus/metrics/exporter/httpserver/HTTPServerTest.java b/prometheus-metrics-exporter-httpserver/src/test/java/io/prometheus/metrics/exporter/httpserver/HTTPServerTest.java
@@ -105,6 +105,19 @@ void metrics() throws IOException {
         "/metrics");
   }
 
+  @Test
+  void metricsCustomPath() throws IOException {
+    run(
+        HTTPServer.builder()
+            .port(0)
+            .registry(new PrometheusRegistry())
+            .metricsHandlerPath("/my-metrics")
+            .executorService(Executors.newFixedThreadPool(1))
+            .buildAndStart(),
+        "200",
+        "/my-metrics");
+  }
+
   @Test
   void registryThrows() throws IOException {
     HTTPServer server =
@@ -147,4 +160,30 @@ void config() throws NoSuchAlgorithmException, IOException {
   void health() throws IOException {
     run(HTTPServer.builder().port(0).buildAndStart(), "200", "/-/healthy");
   }
+
+  @Test
+  void healthEnabled() throws IOException {
+    HttpHandler handler = exchange -> exchange.sendResponseHeaders(204, -1);
+    run(
+        HTTPServer.builder()
+            .port(0)
+            .defaultHandler(handler)
+            .registerHealthHandler(true)
+            .buildAndStart(),
+        "200",
+        "/-/healthy");
+  }
+
+  @Test
+  void healthDisabled() throws IOException {
+    HttpHandler handler = exchange -> exchange.sendResponseHeaders(204, -1);
+    run(
+        HTTPServer.builder()
+            .port(0)
+            .defaultHandler(handler)
+            .registerHealthHandler(false)
+            .buildAndStart(),
+        "204",
+        "/-/healthy");
+  }
 }
