[EXPORTER] Export resource for prometheus

CHANGELOG.md

@@ -17,6 +17,8 @@ Increment the:
 
 * [DEPRECATION] Deprecate ZPAGES
   [#2291](https://github.com/open-telemetry/opentelemetry-cpp/pull/2291)
+* [EXPORTER] Prometheus exporter emit resource attributes
+  [#2301](https://github.com/open-telemetry/opentelemetry-cpp/pull/2301)
 
 ## [1.11.0] 2023-08-21
 

exporters/prometheus/include/opentelemetry/exporters/prometheus/exporter_utils.h

@@ -41,6 +41,28 @@ class PrometheusExporterUtils
    */
   static std::string SanitizeNames(std::string name);
 
+  /**
+   * Append key-value pair to prometheus labels.
+   *
+   * @param name label name
+   * @param value label value
+   * @param labels target labels
+   *
+   * @return true if the attribute should be ignored, false otherwise.
+   */
+  static void AddPrometheusLabel(std::string name,
+                                 std::string value,
+                                 std::vector<::prometheus::ClientMetric::Label> *labels);
+
+  /**
+   * Some attributes should be ignored when converting resource attributes to
+   * prometheus labels.
+   *
+   * @param name resource attribute name
+   * @return true if the attribute should be ignored, false otherwise.
+   */
+  static bool ShouldIgnoreResourceAttribute(const std::string &name);
+
   static opentelemetry::sdk::metrics::AggregationType getAggregationType(
       const opentelemetry::sdk::metrics::PointType &point_type);
 
@@ -50,6 +72,12 @@ class PrometheusExporterUtils
   static ::prometheus::MetricType TranslateType(opentelemetry::sdk::metrics::AggregationType kind,
                                                 bool is_monotonic = true);
 
+  /**
+   * Add a target_info metric to collect resource attributes
+   */
+  static void SetTarget(const sdk::metrics::ResourceMetrics &data,
+                        std::vector<::prometheus::MetricFamily> *output);
+
   /**
    * Set metric data for:
    * Counter => Prometheus Counter
@@ -59,7 +87,8 @@ class PrometheusExporterUtils
                       const opentelemetry::sdk::metrics::PointAttributes &labels,
                       ::prometheus::MetricType type,
                       std::chrono::nanoseconds time,
-                      ::prometheus::MetricFamily *metric_family);
+                      ::prometheus::MetricFamily *metric_family,
+                      const opentelemetry::sdk::resource::Resource *resource);
 
   /**
    * Set metric data for:
@@ -71,14 +100,16 @@ class PrometheusExporterUtils
                       const std::vector<uint64_t> &counts,
                       const opentelemetry::sdk::metrics::PointAttributes &labels,
                       std::chrono::nanoseconds time,
-                      ::prometheus::MetricFamily *metric_family);
+                      ::prometheus::MetricFamily *metric_family,
+                      const opentelemetry::sdk::resource::Resource *resource);
 
   /**
    * Set time and labels to metric data
    */
   static void SetMetricBasic(::prometheus::ClientMetric &metric,
                              std::chrono::nanoseconds time,
-                             const opentelemetry::sdk::metrics::PointAttributes &labels);
+                             const opentelemetry::sdk::metrics::PointAttributes &labels,
+                             const opentelemetry::sdk::resource::Resource *resource);
 
   /**
    * Convert attribute value to string