Add HTTP metrics tag providers

config/accepted-api-changes.json

@@ -273,5 +273,15 @@
     "type": "io.micronaut.configuration.metrics.micrometer.intercept.TimedInterceptor",
     "member": "Constructor io.micronaut.configuration.metrics.micrometer.intercept.TimedInterceptor(io.micrometer.core.instrument.MeterRegistry)",
     "reason": "Removed deprecated code for Micronaut Framework 5"
+  },
+  {
+    "type": "io.micronaut.configuration.metrics.binder.web.HttpMetricsTagProvider",
+    "member": "Class io.micronaut.configuration.metrics.binder.web.HttpMetricsTagProvider",
+    "reason": "Add request-aware HTTP metrics tag provider extension point"
+  },
+  {
+    "type": "io.micronaut.configuration.metrics.binder.web.HttpMetricsTagProvider",
+    "member": "Method io.micronaut.configuration.metrics.binder.web.HttpMetricsTagProvider.getTags(io.micronaut.http.HttpRequest,io.micronaut.http.HttpResponse,java.lang.Throwable)",
+    "reason": "Add request-aware HTTP metrics tag provider extension point"
   }
 ]

micrometer-core/src/main/java/io/micronaut/configuration/metrics/binder/web/ClientMetricsFilter.java

@@ -31,6 +31,7 @@
 import io.micronaut.http.filter.HttpClientFilter;
 import jakarta.inject.Provider;
 
+import java.util.List;
 import java.util.Optional;
 
 import static io.micronaut.core.util.StringUtils.FALSE;
@@ -51,12 +52,16 @@ final class ClientMetricsFilter {
 
     private static final String START_ATTRIBUTE = ClientMetricsFilter.class.getName() + ".START_ATTRIBUTE";
     private final Provider<MeterRegistry> meterRegistryProvider;
+    private final List<HttpMetricsTagProvider> tagProviders;
 
     /**
-     * @param meterRegistryProvider the meter registry provider
+     * @param meterRegistryProvider The meter registry provider
+     * @param tagProviders          The HTTP metrics tag providers
      */
-    public ClientMetricsFilter(Provider<MeterRegistry> meterRegistryProvider) {
+    public ClientMetricsFilter(Provider<MeterRegistry> meterRegistryProvider,
+                               List<HttpMetricsTagProvider> tagProviders) {
         this.meterRegistryProvider = meterRegistryProvider;
+        this.tagProviders = tagProviders;
     }
 
     @RequestFilter
@@ -77,12 +82,14 @@ void doException(HttpRequest<?> request, Throwable throwable) {
     private WebMetricsHelper createHelper(HttpRequest<?> request) {
         return new WebMetricsHelper(
             meterRegistryProvider.get(),
+            request,
             resolvePath(request),
             request.getAttribute(START_ATTRIBUTE, Long.class).orElseGet(System::nanoTime),
             request.getMethod().toString(),
             HttpClientMeterConfig.REQUESTS_METRIC,
             resolveServiceID(request),
-            true
+            true,
+            tagProviders
         );
     }
 

micrometer-core/src/main/java/io/micronaut/configuration/metrics/binder/web/HttpMetricsTagProvider.java

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2017-2026 original 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 io.micronaut.configuration.metrics.binder.web;
+
+import io.micrometer.core.instrument.Tag;
+import io.micronaut.http.HttpRequest;
+import io.micronaut.http.HttpResponse;
+import org.jspecify.annotations.Nullable;
+
+/**
+ * Provides custom tags for HTTP client and server request metrics.
+ *
+ * @since 6.0.0
+ */
+@FunctionalInterface
+public interface HttpMetricsTagProvider {
+
+    /**
+     * Resolve additional tags for an HTTP request metric.
+     *
+     * @param request The HTTP request
+     * @param response The HTTP response, if available
+     * @param throwable The request failure, if available
+     * @return Additional tags for the request metric
+     */
+    Iterable<Tag> getTags(HttpRequest<?> request, @Nullable HttpResponse<?> response, @Nullable Throwable throwable);
+}

micrometer-core/src/main/java/io/micronaut/configuration/metrics/binder/web/ServerMetricsFilter.java

@@ -31,6 +31,7 @@
 import io.micronaut.web.router.UriRouteMatch;
 import jakarta.inject.Provider;
 
+import java.util.List;
 import java.util.Optional;
 import java.util.function.Supplier;
 
@@ -57,14 +58,19 @@ final class ServerMetricsFilter {
     private final Supplier<MeterRegistry> meterRegistryProvider;
 
     private final boolean reportClientErrorURIs;
+    private final List<HttpMetricsTagProvider> tagProviders;
 
     /**
      * @param meterRegistryProvider  the meter registry provider
      * @param clientErrorsUrisConfig the client errors
+     * @param tagProviders           The HTTP metrics tag providers
      */
-    public ServerMetricsFilter(Provider<MeterRegistry> meterRegistryProvider, HttpMetricsConfig.ClientErrorsUrisConfig clientErrorsUrisConfig) {
+    public ServerMetricsFilter(Provider<MeterRegistry> meterRegistryProvider,
+                               HttpMetricsConfig.ClientErrorsUrisConfig clientErrorsUrisConfig,
+                               List<HttpMetricsTagProvider> tagProviders) {
         this.meterRegistryProvider = SupplierUtil.memoized(meterRegistryProvider::get);
         this.reportClientErrorURIs = clientErrorsUrisConfig.enabled();
+        this.tagProviders = tagProviders;
     }
 
     private String resolvePath(HttpRequest<?> request) {
@@ -83,12 +89,14 @@ void onRequest(HttpRequest<?> request) {
     void onResponse(HttpRequest<?> request, HttpResponse<?> response) {
         WebMetricsHelper httpResponseWebMetricsPublisher = new WebMetricsHelper(
             meterRegistryProvider.get(),
+            request,
             resolvePath(request),
             request.getAttribute(START_ATTRIBUTE, Long.class).orElseGet(System::nanoTime),
             request.getMethod().toString(),
             HttpServerMeterConfig.REQUESTS_METRIC,
             null,
-            reportClientErrorURIs
+            reportClientErrorURIs,
+            tagProviders
         );
         httpResponseWebMetricsPublisher.onResponse(response);
     }

micrometer-core/src/main/java/io/micronaut/configuration/metrics/binder/web/WebMetricsHelper.java

@@ -18,17 +18,19 @@
 import io.micrometer.core.instrument.MeterRegistry;
 import io.micrometer.core.instrument.Tag;
 import io.micronaut.core.annotation.Internal;
-import org.jspecify.annotations.NonNull;
-import org.jspecify.annotations.Nullable;
 import io.micronaut.http.HttpAttributes;
+import io.micronaut.http.HttpRequest;
 import io.micronaut.http.HttpResponse;
 import io.micronaut.http.HttpResponseProvider;
 import io.micronaut.http.HttpStatus;
 import io.micronaut.http.exceptions.HttpStatusException;
 import io.micronaut.web.router.ErrorRouteInfo;
 import io.micronaut.web.router.RouteMatch;
+import org.jspecify.annotations.NonNull;
+import org.jspecify.annotations.Nullable;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import static java.util.concurrent.TimeUnit.NANOSECONDS;
@@ -56,15 +58,18 @@
     private static final String SERVICE_ID = "serviceId";
 
     private final MeterRegistry meterRegistry;
+    private final HttpRequest<?> request;
     private final String requestPath;
     private final long start;
     private final String httpMethod;
     private final String metricName;
     private final String serviceID;
     private final boolean reportClientErrorURIs;
+    private final List<HttpMetricsTagProvider> tagProviders;
 
     /**
      * @param meterRegistry         MeterRegistry bean
+     * @param request               The HTTP request
      * @param requestPath           The request path
      * @param start                 The start time of the request
      * @param httpMethod            The HTTP method name used
@@ -72,38 +77,63 @@
      * @param serviceID             The ID of the service called in the request
      * @param reportClientErrorURIs Whether client errors provide uris or not
      */
     WebMetricsHelper(MeterRegistry meterRegistry,
+                     HttpRequest<?> request,
                      String requestPath,
                      long start,
                      String httpMethod,
                      String metricName,
                      String serviceID,
-                     boolean reportClientErrorURIs) {
+                     boolean reportClientErrorURIs,
+                     List<HttpMetricsTagProvider> tagProviders) {
         this.meterRegistry = meterRegistry;
+        this.request = request;
         this.requestPath = requestPath;
         this.start = start;
         this.httpMethod = httpMethod;
         this.metricName = metricName;
         this.serviceID = serviceID;
         this.reportClientErrorURIs = reportClientErrorURIs;
+        this.tagProviders = tagProviders;
+    }
+
+    /**
+     * @param meterRegistry         MeterRegistry bean
+     * @param request               The HTTP request
+     * @param requestPath           The request path
+     * @param start                 The start time of the request
+     * @param httpMethod            The HTTP method name used
+     * @param metricName            The metric name
+     * @param serviceID             The ID of the service called in the request
+     * @param reportClientErrorURIs Whether client errors provide uris or not
+     */
+    WebMetricsHelper(MeterRegistry meterRegistry,
+                     HttpRequest<?> request,
+                     String requestPath,
+                     long start,
+                     String httpMethod,
+                     String metricName,
+                     String serviceID,
+                     boolean reportClientErrorURIs) {
+        this(meterRegistry, request, requestPath, start, httpMethod, metricName, serviceID, reportClientErrorURIs, Collections.emptyList());
     }
 
     /**
      * Get the tags for the metrics based on request shape.
      *
-     * @param httpResponse The HTTP response
+     * @param httpResponse The HTTP response, if available
      * @param httpMethod   The name of the HTTP method (GET, POST, etc)
      * @param requestPath  The request path (/foo, /foo/bar, etc)
      * @param throwable    The throwable (optional)
      * @param serviceId         the service ID
      * @return A list of Tag objects
      */
-    private static List<Tag> getTags(HttpResponse<?> httpResponse,
-                                     String httpMethod,
-                                     String requestPath,
-                                     Throwable throwable,
-                                     String serviceId,
-                                     boolean reportClientErrorURIs) {
+    private List<Tag> getTags(@Nullable HttpResponse<?> httpResponse,
+                              String httpMethod,
+                              String requestPath,
+                              Throwable throwable,
+                              String serviceId,
+                              boolean reportClientErrorURIs) {
         List<@NonNull Tag> tags = new ArrayList<>(5);
         Tag t1 = method(httpMethod);
         if (t1 != null) {
@@ -116,6 +146,9 @@
         if (t5 != null) {
             tags.add(t5);
         }
+        for (HttpMetricsTagProvider tagProvider : tagProviders) {
+            tagProvider.getTags(request, httpResponse, throwable).forEach(tags::add);
+        }
         return tags;
     }
 
@@ -154,7 +187,7 @@
      * @return Tag of URI
      */
     @NonNull
-    private static Tag uri(HttpResponse<?> httpResponse, String path, boolean reportClientErrorURIs) {
+    private static Tag uri(@Nullable HttpResponse<?> httpResponse, String path, boolean reportClientErrorURIs) {
         if (httpResponse != null) {
             int code = httpResponse.code();
             if (code >= 300 && code < 400) {
@@ -280,10 +313,10 @@
     /**
      * Registers the error timer for a web request when an exception occurs.
      *
-     * @param httpResponse existing response object.
+     * @param httpResponse existing response object, if available.
      * @param throwable    exception that occurred
      */
-    public void error(HttpResponse<?> httpResponse, Throwable throwable) {
+    public void error(@Nullable HttpResponse<?> httpResponse, Throwable throwable) {
         if (httpResponse == null && throwable instanceof HttpResponseProvider httpResponseProvider) {
             httpResponse = httpResponseProvider.getResponse();
         }

micrometer-core/src/test/groovy/io/micronaut/configuration/metrics/binder/web/HttpMetricsSpec.groovy

@@ -1,6 +1,7 @@
 package io.micronaut.configuration.metrics.binder.web
 
 import groovy.transform.InheritConstructors
+import io.micrometer.core.instrument.Tag
 import io.micrometer.common.lang.NonNull
 import io.micrometer.core.instrument.MeterRegistry
 import io.micrometer.core.instrument.Timer
@@ -12,10 +13,12 @@ import io.micronaut.configuration.metrics.binder.web.config.HttpServerMeterConfi
 import io.micronaut.context.ApplicationContext
 import io.micronaut.context.annotation.Requires
 import io.micronaut.core.util.CollectionUtils
+import io.micronaut.http.HttpRequest
 import io.micronaut.http.HttpResponse
 import io.micronaut.http.annotation.Controller
 import io.micronaut.http.annotation.Error
 import io.micronaut.http.annotation.Get
+import io.micronaut.http.annotation.Header
 import io.micronaut.http.client.annotation.Client
 import io.micronaut.http.client.exceptions.HttpClientResponseException
 import io.micronaut.http.uri.UriBuilder
@@ -29,6 +32,7 @@ import reactor.core.publisher.Flux
 import spock.lang.PendingFeature
 import spock.lang.Specification
 
+import jakarta.inject.Singleton
 import jakarta.validation.constraints.NotBlank
 
 import static io.micronaut.configuration.metrics.micrometer.MeterRegistryFactory.MICRONAUT_METRICS_BINDERS
@@ -38,6 +42,32 @@ import static io.micronaut.http.HttpStatus.NOT_FOUND
 
 class HttpMetricsSpec extends Specification {
 
+    void "test client and server metrics include custom tags"() {
+        when:
+        EmbeddedServer embeddedServer = ApplicationContext.run(EmbeddedServer, ['spec.name': getClass().getSimpleName()])
+        def context = embeddedServer.applicationContext
+        TestClient client = context.getBean(TestClient)
+
+        then:
+        client.tagged("custom-value") == 'ok custom-value'
+
+        when:
+        MeterRegistry registry = context.getBean(MeterRegistry)
+
+        then:
+        registry.get(HttpServerMeterConfig.REQUESTS_METRIC)
+            .tags('uri', '/test-http-metrics/tagged', 'custom', 'custom-value')
+            .timer()
+            .count() == 1
+        registry.get(HttpClientMeterConfig.REQUESTS_METRIC)
+            .tags('uri', '/test-http-metrics/tagged', 'custom', 'custom-value')
+            .timer()
+            .count() == 1
+
+        cleanup:
+        embeddedServer.close()
+    }
+
     void "test client / server metrics with #cfg #setting"() {
         when:
         EmbeddedServer embeddedServer = ApplicationContext.run(EmbeddedServer, [(cfg): setting, 'spec.name': getClass().getSimpleName()])
@@ -285,6 +315,9 @@ class HttpMetricsSpec extends Specification {
         @Get("/test-http-metrics/{id}")
         String template(String id)
 
+        @Get("/test-http-metrics/tagged")
+        String tagged(@Header("X-Custom-Tag") String customTag)
+
         @Get("/test-http-metrics/error")
         HttpResponse error()
 
@@ -310,6 +343,9 @@ class HttpMetricsSpec extends Specification {
         @Get("/test-http-metrics/{id}")
         String template(String id) { "ok " + id }
 
+        @Get("/test-http-metrics/tagged")
+        String tagged(@Header("X-Custom-Tag") String customTag) { "ok " + customTag }
+
         @Get("/test-http-metrics/error")
         HttpResponse error() {
             HttpResponse.status(CONFLICT)
@@ -367,6 +403,16 @@ class HttpMetricsSpec extends Specification {
 
     }
 
+    @Requires(property = "spec.name", value = "HttpMetricsSpec")
+    @Singleton
+    static class TestHttpMetricsTagProvider implements HttpMetricsTagProvider {
+
+        @Override
+        Iterable<Tag> getTags(HttpRequest<?> request, HttpResponse<?> response, Throwable throwable) {
+            return [Tag.of("custom", request.headers.get("X-Custom-Tag") ?: "none")]
+        }
+    }
+
     @InheritConstructors
     static class MyException extends RuntimeException {
     }