[Exporter.Prometheus] Add ResourceConstantLabels

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/.publicApi/PublicAPI.Unshipped.txt

@@ -4,6 +4,8 @@ OpenTelemetry.Exporter.PrometheusAspNetCoreOptions
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.DisableTotalNameSuffixForCounters.get -> bool
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.DisableTotalNameSuffixForCounters.set -> void
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.PrometheusAspNetCoreOptions() -> void
+OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.ResourceConstantLabels.get -> System.Func<string!, bool>?
+OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.ResourceConstantLabels.set -> void
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.ScopeInfoEnabled.get -> bool
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.ScopeInfoEnabled.set -> void
 OpenTelemetry.Exporter.PrometheusAspNetCoreOptions.ScrapeEndpointPath.get -> string?

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/CHANGELOG.md

@@ -31,6 +31,11 @@ Notes](../../RELEASENOTES.md).
   disable the `target_info` metric in Prometheus metrics. Defaults to `true`.
   ([#7438](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7438))
 
+* Add `PrometheusAspNetCoreOptions.ResourceConstantLabels` property to select
+  resource attributes to add to each metric as constant labels. Defaults to
+  `null` (no resource attributes are added as metric labels).
+  ([#7471](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7471))
+
 ## 1.16.0-beta.1
 
 Released 2026-Jun-10

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/PrometheusAspNetCoreOptions.cs

@@ -58,5 +58,20 @@ public bool TargetInfoEnabled
         set => this.ExporterOptions.TargetInfoEnabled = value;
     }
 
+    /// <summary>
+    /// Gets or sets a predicate used to select which resource attributes are added to each metric as constant labels.
+    /// The predicate is invoked with the resource attribute key and should return <see langword="true"/> to include the
+    /// attribute. Default value: <see langword="null"/> (no resource attributes are added as metric labels).
+    /// </summary>
+    /// <remarks>
+    /// Note: Resource attributes copied as metric labels are always included in the <c>target_info</c> metric
+    /// regardless of this predicate.
+    /// </remarks>
+    public Func<string, bool>? ResourceConstantLabels
+    {
+        get => this.ExporterOptions.ResourceConstantLabels;
+        set => this.ExporterOptions.ResourceConstantLabels = value;
+    }
+
     internal PrometheusExporterOptions ExporterOptions { get; } = new();
 }

src/OpenTelemetry.Exporter.Prometheus.AspNetCore/README.md

@@ -148,6 +148,26 @@ Specifies whether to produce a
 [`target_info`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/compatibility/prometheus_and_openmetrics.md#resource-attributes-1)
 metric. Default value: `true`. Set to `false` to disable the `target_info` metric.
 
+### ResourceConstantLabels
+
+A predicate used to select which
+[resource attributes](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/prometheus.md#resource-attributes-as-metric-labels)
+are added to each metric as constant labels. The predicate is invoked with the
+resource attribute key and should return `true` to include the attribute.
+Default value: `null` (no resource attributes are added as metric labels).
+Resource attributes copied as metric labels are always included in the
+`target_info` metric regardless of this predicate.
+
+```csharp
+services.AddOpenTelemetry()
+    .WithMetrics(builder => builder
+        .AddPrometheusExporter(options =>
+        {
+            // Add all resource attributes as metric labels.
+            options.ResourceConstantLabels = static _ => true;
+        }));
+```
+
 ## Troubleshooting
 
 This component uses an

src/OpenTelemetry.Exporter.Prometheus.HttpListener/.publicApi/PublicAPI.Unshipped.txt

@@ -7,6 +7,8 @@ OpenTelemetry.Exporter.PrometheusHttpListenerOptions.DisableTotalNameSuffixForCo
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions.DisableTotalNameSuffixForCounters.set -> void
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions.ScopeInfoEnabled.get -> bool
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions.ScopeInfoEnabled.set -> void
+OpenTelemetry.Exporter.PrometheusHttpListenerOptions.ResourceConstantLabels.get -> System.Func<string!, bool>?
+OpenTelemetry.Exporter.PrometheusHttpListenerOptions.ResourceConstantLabels.set -> void
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions.TargetInfoEnabled.get -> bool
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions.TargetInfoEnabled.set -> void
 OpenTelemetry.Exporter.PrometheusHttpListenerOptions.PrometheusHttpListenerOptions() -> void

src/OpenTelemetry.Exporter.Prometheus.HttpListener/CHANGELOG.md

@@ -34,6 +34,11 @@ Notes](../../RELEASENOTES.md).
   disable the `target_info` metric in Prometheus metrics. Defaults to `true`.
   ([#7438](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7438))
 
+* Add `PrometheusHttpListenerOptions.ResourceConstantLabels` property to select
+  resource attributes to add to each metric as constant labels. Defaults to
+  `null` (no resource attributes are added as metric labels).
+  ([#7471](https://github.com/open-telemetry/opentelemetry-dotnet/pull/7471))
+
 ## 1.16.0-beta.1
 
 Released 2026-Jun-10

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusCollectionManager.cs

@@ -18,11 +18,14 @@ internal sealed class PrometheusCollectionManager
     private readonly PrometheusExporter exporter;
     private readonly bool scopeInfoEnabled;
     private readonly bool targetInfoEnabled;
+    private readonly Func<string, bool>? resourceConstantLabelsFilter;
     private readonly TimeSpan scrapeResponseCacheDuration;
     private readonly long baseTimestamp = Stopwatch.GetTimestamp();
     private readonly PrometheusExporter.ExportFunc onCollectRef;
     private readonly Dictionary<Metric, PrometheusMetric> metricsCache;
     private int metricsCacheCount;
+    private IReadOnlyList<KeyValuePair<string, object>>? resourceConstantLabels;
+    private bool resourceConstantLabelsComputed;
     private int globalLockState;
     private CollectionContext? collectionContext;
     private CollectionContext? onCollectContext;
@@ -33,6 +36,7 @@ public PrometheusCollectionManager(PrometheusExporter exporter)
         this.exporter = exporter;
         this.scopeInfoEnabled = this.exporter.ScopeInfoEnabled;
         this.targetInfoEnabled = this.exporter.TargetInfoEnabled;
+        this.resourceConstantLabelsFilter = this.exporter.ResourceConstantLabels;
         this.scrapeResponseCacheDuration = TimeSpan.FromMilliseconds(this.exporter.ScrapeResponseCacheDurationMilliseconds);
         this.onCollectRef = this.OnCollect;
         this.metricsCache = [];
@@ -357,7 +361,9 @@ private bool TryWriteResponse(in PrometheusProtocol protocol, PrometheusProtocol
 
             var cursor = this.targetInfoEnabled ? this.WriteTargetInfo(serializer, state) : 0;
             var metricStates = this.GetMetricStates(serializer, metrics);
-            var options = new TextFormatSerializerOptions(suppressScopeInfo: !this.scopeInfoEnabled);
+            var options = new TextFormatSerializerOptions(
+                suppressScopeInfo: !this.scopeInfoEnabled,
+                resourceConstantLabels: this.GetResourceConstantLabels());
 
             foreach (var metricState in metricStates)
             {
@@ -477,6 +483,32 @@ state.GeneratedAtElapsed is { } generatedAtElapsed &&
     private PrometheusProtocolState GetProtocolState(in PrometheusProtocol protocol)
         => this.protocolStates.GetOrAdd(protocol, static _ => new());
 
+    private IReadOnlyList<KeyValuePair<string, object>>? GetResourceConstantLabels()
+    {
+        if (!this.resourceConstantLabelsComputed)
+        {
+            if (this.resourceConstantLabelsFilter is { } filter)
+            {
+                List<KeyValuePair<string, object>>? labels = null;
+
+                foreach (var attribute in this.exporter.Resource.Attributes)
+                {
+                    if (filter(attribute.Key))
+                    {
+                        labels ??= [];
+                        labels.Add(attribute);
+                    }
+                }
+
+                this.resourceConstantLabels = labels;
+            }
+
+            this.resourceConstantLabelsComputed = true;
+        }
+
+        return this.resourceConstantLabels;
+    }
+
     private int WriteTargetInfo(TextFormatSerializer serializer, PrometheusProtocolState state)
     {
         while (true)

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusExporter.cs

@@ -27,6 +27,7 @@ public PrometheusExporter(PrometheusExporterOptions options)
         this.ScrapeResponseCacheDurationMilliseconds = options.ScrapeResponseCacheDurationMilliseconds;
         this.TargetInfoEnabled = options.TargetInfoEnabled;
         this.DisableTotalNameSuffixForCounters = options.DisableTotalNameSuffixForCounters;
+        this.ResourceConstantLabels = options.ResourceConstantLabels;
 
         this.CollectionManager = new PrometheusCollectionManager(this);
     }
@@ -52,6 +53,8 @@ public PrometheusExporter(PrometheusExporterOptions options)
 
     internal bool DisableTotalNameSuffixForCounters { get; }
 
+    internal Func<string, bool>? ResourceConstantLabels { get; }
+
     internal Resource Resource
     {
         get => field ??= this.ParentProvider.GetResource();

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/PrometheusExporterOptions.cs

@@ -49,4 +49,11 @@ public int ScrapeResponseCacheDurationMilliseconds
     /// Gets or sets a value indicating whether addition of _total suffix for counter metric names is disabled. Default value: <see langword="false"/>.
     /// </summary>
     public bool DisableTotalNameSuffixForCounters { get; set; }
+
+    /// <summary>
+    /// Gets or sets a predicate used to select which resource attributes are added to each metric as constant labels.
+    /// The predicate is invoked with the resource attribute key and should return <see langword="true"/> to include the
+    /// attribute. Default value: <see langword="null"/> (no resource attributes are added as metric labels).
+    /// </summary>
+    public Func<string, bool>? ResourceConstantLabels { get; set; }
 }

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/Serialization/TextFormatSerializer.cs

@@ -642,28 +642,37 @@ internal int WriteTags(
         List<string>? writtenOutputKeys = null;
         var wroteLabel = false;
 
+        var resourceConstantLabels = options.ResourceConstantLabels;
+        var hasResourceConstantLabels = resourceConstantLabels is { Count: > 0 };
+
         if (writeEnclosingBraces)
         {
             buffer[cursor++] = unchecked((byte)'{');
         }
 
-        if (!options.SuppressScopeInfo)
-        {
-            WriteScopeLabels();
-        }
-
-        if (TryWritePointTags())
+        // The fast path writes scope labels and point tags directly to the buffer. It cannot
+        // account for resource constant labels (which may collide with, and therefore need to be
+        // merged with, point tags), so it is skipped whenever any are present.
+        if (!hasResourceConstantLabels)
         {
-            if (writeEnclosingBraces)
+            if (!options.SuppressScopeInfo)
             {
-                buffer[cursor++] = unchecked((byte)'}');
+                WriteScopeLabels();
             }
-            else if (wroteLabel)
+
+            if (TryWritePointTags())
             {
-                buffer[cursor++] = unchecked((byte)',');
-            }
+                if (writeEnclosingBraces)
+                {
+                    buffer[cursor++] = unchecked((byte)'}');
+                }
+                else if (wroteLabel)
+                {
+                    buffer[cursor++] = unchecked((byte)',');
+                }
 
-            return cursor;
+                return cursor;
+            }
         }
 
         cursor = startCursor;
@@ -682,6 +691,14 @@ internal int WriteTags(
             this.AddLabel(tag.Key, tag.Value, ref labels, reservedOutputKeys);
         }
 
+        if (hasResourceConstantLabels)
+        {
+            foreach (var resourceLabel in resourceConstantLabels!)
+            {
+                this.AddLabel(resourceLabel.Key, resourceLabel.Value, ref labels, reservedOutputKeys);
+            }
+        }
+
         return WriteLabels(buffer, cursor, labels, writeEnclosingBraces);
 
         void WriteScopeLabels()

src/OpenTelemetry.Exporter.Prometheus.HttpListener/Internal/Shared/Serialization/TextFormatSerializerOptions.cs

@@ -13,12 +13,21 @@ internal readonly struct TextFormatSerializerOptions
     /// </summary>
     public readonly bool SuppressScopeInfo; // Inverted so the default struct is the default value (false = included).
 
+    /// <summary>
+    /// The resource attributes to add to each metric as constant labels, or <see langword="null"/> if none.
+    /// </summary>
+    public readonly IReadOnlyList<KeyValuePair<string, object>>? ResourceConstantLabels;
+
     /// <summary>
     /// Initializes a new instance of the <see cref="TextFormatSerializerOptions"/> struct.
     /// </summary>
     /// <param name="suppressScopeInfo">Whether the scope information is suppressed from the scrape response.</param>
-    public TextFormatSerializerOptions(bool suppressScopeInfo)
+    /// <param name="resourceConstantLabels">The resource attributes to add to each metric as constant labels, or <see langword="null"/> if none.</param>
+    public TextFormatSerializerOptions(
+        bool suppressScopeInfo,
+        IReadOnlyList<KeyValuePair<string, object>>? resourceConstantLabels)
     {
         this.SuppressScopeInfo = suppressScopeInfo;
+        this.ResourceConstantLabels = resourceConstantLabels;
     }
 }

src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerMeterProviderBuilderExtensions.cs

@@ -71,6 +71,7 @@ private static BaseExportingMetricReader BuildPrometheusHttpListenerMetricReader
             ScrapeResponseCacheDurationMilliseconds = options.ScrapeResponseCacheDurationMilliseconds,
             TargetInfoEnabled = options.TargetInfoEnabled,
             DisableTotalNameSuffixForCounters = options.DisableTotalNameSuffixForCounters,
+            ResourceConstantLabels = options.ResourceConstantLabels,
         });
 
         var reader = new BaseExportingMetricReader(exporter)

src/OpenTelemetry.Exporter.Prometheus.HttpListener/PrometheusHttpListenerOptions.cs

@@ -99,5 +99,16 @@ public int ScrapeResponseCacheDurationMilliseconds
     /// </summary>
     public bool TargetInfoEnabled { get; set; } = true;
 
+    /// <summary>
+    /// Gets or sets a predicate used to select which resource attributes are added to each metric as constant labels.
+    /// The predicate is invoked with the resource attribute key and should return <see langword="true"/> to include the
+    /// attribute. Default value: <see langword="null"/> (no resource attributes are added as metric labels).
+    /// </summary>
+    /// <remarks>
+    /// Note: Resource attributes copied as metric labels are always included in the <c>target_info</c> metric
+    /// regardless of this predicate.
+    /// </remarks>
+    public Func<string, bool>? ResourceConstantLabels { get; set; }
+
     internal Action<PrometheusHttpListenerOptions, System.Net.HttpListener>? ConfigureHttpListener { get; set; }
 }

src/OpenTelemetry.Exporter.Prometheus.HttpListener/README.md

@@ -64,6 +64,8 @@ variables.
 * `ScrapeEndpointPath`: Defines the Prometheus scrape endpoint path.
   (default `"/metrics"`).
 * `TargetInfoEnabled`: Whether to produce a `target_info` metric (default `true`).
+* `ResourceConstantLabels`: A predicate selecting which resource attributes are
+  added to each metric as constant labels (default `null`).
 * `DisableTotalNameSuffixForCounters`: Whether to disable the `_total` suffix for
   counter metrics (default `false`).
 * `DisableTimestamp`: Whether to disable the timestamp for metrics (default `false`).
@@ -115,6 +117,27 @@ Specifies whether to produce a
 [`target_info`](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/compatibility/prometheus_and_openmetrics.md#resource-attributes-1)
 metric. Default value: `true`. Set to `false` to disable the `target_info` metric.
 
+### ResourceConstantLabels
+
+A predicate used to select which
+[resource attributes](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/metrics/sdk_exporters/prometheus.md#resource-attributes-as-metric-labels)
+are added to each metric as constant labels. The predicate is invoked with the
+resource attribute key and should return `true` to include the attribute.
+Default value: `null` (no resource attributes are added as metric labels).
+Resource attributes copied as metric labels are always included in the
+`target_info` metric regardless of this predicate.
+
+```csharp
+var meterProvider = Sdk.CreateMeterProviderBuilder()
+    .AddMeter(MyMeter.Name)
+    .AddPrometheusHttpListener(options =>
+    {
+        // Add all resource attributes as metric labels.
+        options.ResourceConstantLabels = static _ => true;
+    })
+    .Build();
+```
+
 ## Troubleshooting
 
 This component uses an

test/OpenTelemetry.Exporter.Prometheus.AspNetCore.Tests/PrometheusExporterMiddlewareTests.cs

@@ -62,6 +62,26 @@ public async Task RunWithTargetInfoEnabledConfigured(bool targetInfoEnabled)
         await Verify(output, "text", PrometheusSerializerTests.VerifySettings).UseParameters(targetInfoEnabled);
     }
 
+    [Theory]
+    [InlineData("all")]
+    [InlineData("service_name")]
+    [InlineData("none")]
+    public async Task RunWithResourceConstantLabelsConfigured(string filter)
+    {
+        var output = await RunPrometheusExporterMiddlewareIntegrationTest(
+            "/metrics",
+            app => app.UseOpenTelemetryPrometheusScrapingEndpoint(),
+            services => services.Configure<PrometheusAspNetCoreOptions>(o => o.ResourceConstantLabels = filter switch
+            {
+                "all" => static _ => true,
+                "service_name" => static key => key == "service.name",
+                _ => static _ => false,
+            }),
+            assertResponseContent: false);
+
+        await Verify(output, "text", PrometheusSerializerTests.VerifySettings).UseParameters(filter);
+    }
+
     [Fact]
     public async Task RunWithCustomScrapeEndpointPath()
     {

test/OpenTelemetry.Exporter.Prometheus.HttpListener.Tests/PrometheusHttpListenerTests.cs

@@ -62,6 +62,28 @@ public async Task RunHttpServerWithTargetInfoEnabledConfigured(bool targetInfoEn
         await Verify(output, "text", PrometheusSerializerTests.VerifySettings).UseParameters(targetInfoEnabled);
     }
 
+    [Theory]
+    [InlineData("all")]
+    [InlineData("service_name")]
+    [InlineData("none")]
+    public async Task RunHttpServerWithResourceConstantLabelsConfigured(string filter)
+    {
+        var output = await RunPrometheusExporterHttpServerIntegrationTest(
+            configureListener: (options) =>
+            {
+                options.ResourceConstantLabels = filter switch
+                {
+                    "all" => static _ => true,
+                    "service_name" => static key => key == "service.name",
+                    _ => static _ => false,
+                };
+                return options.Port;
+            },
+            assertResponseContent: false);
+
+        await Verify(output, "text", PrometheusSerializerTests.VerifySettings).UseParameters(filter);
+    }
+
     [Fact]
     public async Task RunHttpServerWithNoMetrics()
     {