[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)
 * [EXPORTER] Remove explicit timestamps from metric points exported by Prometheus
   [#2324](https://github.com/open-telemetry/opentelemetry-cpp/pull/2324)
 * [EXPORTER] Handle attribute key collisions caused by sanitation

exporters/prometheus/include/opentelemetry/exporters/prometheus/collector.h

@@ -31,7 +31,7 @@ class PrometheusCollector : public prometheus_client::Collectable
    * This constructor initializes the collection for metrics to export
    * in this class with default capacity
    */
-  explicit PrometheusCollector(sdk::metrics::MetricReader *reader);
+  explicit PrometheusCollector(sdk::metrics::MetricReader *reader, bool populate_target_info);
 
   /**
    * Collects all metrics data from metricsToCollect collection.
@@ -42,6 +42,7 @@ class PrometheusCollector : public prometheus_client::Collectable
 
 private:
   sdk::metrics::MetricReader *reader_;
+  bool populate_target_info_;
 
   /*
    * Lock when operating the metricsToCollect collection

exporters/prometheus/include/opentelemetry/exporters/prometheus/exporter_options.h

@@ -22,6 +22,9 @@ struct PrometheusExporterOptions
 
   // The endpoint the Prometheus backend can collect metrics from
   std::string url;
+
+  // Populating target_info
+  bool populate_target_info = true;
 };
 
 }  // namespace metrics

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

@@ -26,12 +26,25 @@ class PrometheusExporterUtils
    * to Prometheus metrics data collection
    *
    * @param records a collection of metrics in OpenTelemetry
+   * @param populate_target_info whether to populate target_info
    * @return a collection of translated metrics that is acceptable by Prometheus
    */
   static std::vector<::prometheus::MetricFamily> TranslateToPrometheus(
-      const sdk::metrics::ResourceMetrics &data);
+      const sdk::metrics::ResourceMetrics &data,
+      bool populate_target_info = true);
 
 private:
+  /**
+   * Append key-value pair to prometheus labels.
+   *
+   * @param name label name
+   * @param value label value
+   * @param labels target labels
+   */
+  static void AddPrometheusLabel(std::string name,
+                                 std::string value,
+                                 std::vector<::prometheus::ClientMetric::Label> *labels);
+
   static opentelemetry::sdk::metrics::AggregationType getAggregationType(
       const opentelemetry::sdk::metrics::PointType &point_type);
 
@@ -41,6 +54,12 @@ 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
@@ -49,7 +68,8 @@ class PrometheusExporterUtils
   static void SetData(std::vector<T> values,
                       const opentelemetry::sdk::metrics::PointAttributes &labels,
                       ::prometheus::MetricType type,
-                      ::prometheus::MetricFamily *metric_family);
+                      ::prometheus::MetricFamily *metric_family,
+                      const opentelemetry::sdk::resource::Resource *resource);
 
   /**
    * Set metric data for:
@@ -60,13 +80,15 @@ class PrometheusExporterUtils
                       const std::vector<double> &boundaries,
                       const std::vector<uint64_t> &counts,
                       const opentelemetry::sdk::metrics::PointAttributes &labels,
-                      ::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,
-                             const opentelemetry::sdk::metrics::PointAttributes &labels);
+                             const opentelemetry::sdk::metrics::PointAttributes &labels,
+                             const opentelemetry::sdk::resource::Resource *resource);
 
   /**
    * Convert attribute value to string

exporters/prometheus/src/collector.cc

@@ -17,7 +17,10 @@ namespace metrics
  * This constructor initializes the collection for metrics to export
  * in this class with default capacity
  */
-PrometheusCollector::PrometheusCollector(sdk::metrics::MetricReader *reader) : reader_(reader) {}
+PrometheusCollector::PrometheusCollector(sdk::metrics::MetricReader *reader,
+                                         bool populate_target_info)
+    : reader_(reader), populate_target_info_(populate_target_info)
+{}
 
 /**
  * Collects all metrics data from metricsToCollect collection.
@@ -36,8 +39,11 @@ std::vector<prometheus_client::MetricFamily> PrometheusCollector::Collect() cons
   collection_lock_.lock();
 
   std::vector<prometheus_client::MetricFamily> result;
-  reader_->Collect([&result](sdk::metrics::ResourceMetrics &metric_data) {
-    auto prometheus_metric_data = PrometheusExporterUtils::TranslateToPrometheus(metric_data);
+
+  bool populate_target_info = populate_target_info_;
+  reader_->Collect([&result, populate_target_info](sdk::metrics::ResourceMetrics &metric_data) {
+    auto prometheus_metric_data =
+        PrometheusExporterUtils::TranslateToPrometheus(metric_data, populate_target_info);
     for (auto &data : prometheus_metric_data)
       result.emplace_back(data);
     return true;

exporters/prometheus/src/exporter.cc

@@ -30,7 +30,8 @@ PrometheusExporter::PrometheusExporter(const PrometheusExporterOptions &options)
     Shutdown();  // set MetricReader in shutdown state.
     return;
   }
-  collector_ = std::shared_ptr<PrometheusCollector>(new PrometheusCollector(this));
+  collector_ = std::shared_ptr<PrometheusCollector>(
+      new PrometheusCollector(this, options_.populate_target_info));
 
   exposer_->RegisterCollectable(collector_);
 }

exporters/prometheus/src/exporter_utils.cc

@@ -1,14 +1,22 @@
 // Copyright The OpenTelemetry Authors
 // SPDX-License-Identifier: Apache-2.0
 
+#include <limits>
 #include <sstream>
+#include <string>
+#include <unordered_map>
+#include <unordered_set>
 #include <utility>
 #include <vector>
+
 #include "prometheus/metric_family.h"
+#include "prometheus/metric_type.h"
 
-#include <prometheus/metric_type.h>
 #include "opentelemetry/exporters/prometheus/exporter_utils.h"
 #include "opentelemetry/sdk/metrics/export/metric_producer.h"
+#include "opentelemetry/sdk/resource/resource.h"
+#include "opentelemetry/sdk/resource/semantic_conventions.h"
+#include "opentelemetry/trace/semantic_conventions.h"
 
 #include "opentelemetry/sdk/common/global_log_handler.h"
 
@@ -22,6 +30,7 @@ namespace metrics
 {
 namespace
 {
+
 /**
  * Sanitize the given metric name by replacing invalid characters with _,
  * ensuring that multiple consecutive _ characters are collapsed to a single _.
@@ -107,11 +116,25 @@ std::string SanitizeName(std::string name)
  * @return a collection of translated metrics that is acceptable by Prometheus
  */
 std::vector<prometheus_client::MetricFamily> PrometheusExporterUtils::TranslateToPrometheus(
-    const sdk::metrics::ResourceMetrics &data)
+    const sdk::metrics::ResourceMetrics &data,
+    bool populate_target_info)
 {
 
   // initialize output vector
+  std::size_t reserve_size = 1;
+  for (const auto &instrumentation_info : data.scope_metric_data_)
+  {
+    reserve_size += instrumentation_info.metric_data_.size();
+  }
+
   std::vector<prometheus_client::MetricFamily> output;
+  output.reserve(reserve_size);
+
+  // Append target_info as the first metric
+  if (populate_target_info)
+  {
+    SetTarget(data, &output);
+  }
 
   for (const auto &instrumentation_info : data.scope_metric_data_)
   {
@@ -147,10 +170,10 @@ std::vector<prometheus_client::MetricFamily> PrometheusExporterUtils::TranslateT
           }
           else
           {
-            sum = nostd::get<int64_t>(histogram_point_data.sum_);
+            sum = static_cast<double>(nostd::get<int64_t>(histogram_point_data.sum_));
           }
           SetData(std::vector<double>{sum, (double)histogram_point_data.count_}, boundaries, counts,
-                  point_data_attr.attributes, &metric_family);
+                  point_data_attr.attributes, &metric_family, data.resource_);
         }
         else if (type == prometheus_client::MetricType::Gauge)
         {
@@ -160,14 +183,14 @@ std::vector<prometheus_client::MetricFamily> PrometheusExporterUtils::TranslateT
             auto last_value_point_data =
                 nostd::get<sdk::metrics::LastValuePointData>(point_data_attr.point_data);
             std::vector<metric_sdk::ValueType> values{last_value_point_data.value_};
-            SetData(values, point_data_attr.attributes, type, &metric_family);
+            SetData(values, point_data_attr.attributes, type, &metric_family, data.resource_);
           }
           else if (nostd::holds_alternative<sdk::metrics::SumPointData>(point_data_attr.point_data))
           {
             auto sum_point_data =
                 nostd::get<sdk::metrics::SumPointData>(point_data_attr.point_data);
             std::vector<metric_sdk::ValueType> values{sum_point_data.value_};
-            SetData(values, point_data_attr.attributes, type, &metric_family);
+            SetData(values, point_data_attr.attributes, type, &metric_family, data.resource_);
           }
           else
           {
@@ -183,7 +206,7 @@ std::vector<prometheus_client::MetricFamily> PrometheusExporterUtils::TranslateT
             auto sum_point_data =
                 nostd::get<sdk::metrics::SumPointData>(point_data_attr.point_data);
             std::vector<metric_sdk::ValueType> values{sum_point_data.value_};
-            SetData(values, point_data_attr.attributes, type, &metric_family);
+            SetData(values, point_data_attr.attributes, type, &metric_family, data.resource_);
           }
           else
           {
@@ -199,6 +222,17 @@ std::vector<prometheus_client::MetricFamily> PrometheusExporterUtils::TranslateT
   return output;
 }
 
+void PrometheusExporterUtils::AddPrometheusLabel(
+    std::string name,
+    std::string value,
+    std::vector<::prometheus::ClientMetric::Label> *labels)
+{
+  prometheus_client::ClientMetric::Label prometheus_label;
+  prometheus_label.name  = std::move(name);
+  prometheus_label.value = std::move(value);
+  labels->emplace_back(std::move(prometheus_label));
+}
+
 metric_sdk::AggregationType PrometheusExporterUtils::getAggregationType(
     const metric_sdk::PointType &point_type)
 {
@@ -252,6 +286,35 @@ prometheus_client::MetricType PrometheusExporterUtils::TranslateType(
   }
 }
 
+void PrometheusExporterUtils::SetTarget(const sdk::metrics::ResourceMetrics &data,
+                                        std::vector<::prometheus::MetricFamily> *output)
+{
+  if (output == nullptr || data.resource_ == nullptr)
+  {
+    return;
+  }
+
+  prometheus_client::MetricFamily metric_family;
+  metric_family.name = "target";
+  metric_family.help = "Target metadata";
+  metric_family.type = prometheus_client::MetricType::Info;
+  metric_family.metric.emplace_back();
+
+  prometheus_client::ClientMetric &metric = metric_family.metric.back();
+  metric.info.value                       = 1.0;
+
+  metric_sdk::PointAttributes empty_attributes;
+  SetMetricBasic(metric, empty_attributes, data.resource_);
+
+  for (auto &label : data.resource_->GetAttributes())
+  {
+    AddPrometheusLabel(SanitizeName(label.first), AttributeValueToString(label.second),
+                       &metric.label);
+  }
+
+  output->emplace_back(std::move(metric_family));
+}
+
 /**
  * Set metric data for:
  * sum => Prometheus Counter
@@ -260,11 +323,12 @@ template <typename T>
 void PrometheusExporterUtils::SetData(std::vector<T> values,
                                       const metric_sdk::PointAttributes &labels,
                                       prometheus_client::MetricType type,
-                                      prometheus_client::MetricFamily *metric_family)
+                                      prometheus_client::MetricFamily *metric_family,
+                                      const opentelemetry::sdk::resource::Resource *resource)
 {
   metric_family->metric.emplace_back();
   prometheus_client::ClientMetric &metric = metric_family->metric.back();
-  SetMetricBasic(metric, labels);
+  SetMetricBasic(metric, labels, resource);
   SetValue(values, type, &metric);
 }
 
@@ -277,21 +341,23 @@ void PrometheusExporterUtils::SetData(std::vector<T> values,
                                       const std::vector<double> &boundaries,
                                       const std::vector<uint64_t> &counts,
                                       const metric_sdk::PointAttributes &labels,
-                                      prometheus_client::MetricFamily *metric_family)
+                                      prometheus_client::MetricFamily *metric_family,
+                                      const opentelemetry::sdk::resource::Resource *resource)
 {
   metric_family->metric.emplace_back();
   prometheus_client::ClientMetric &metric = metric_family->metric.back();
-  SetMetricBasic(metric, labels);
+  SetMetricBasic(metric, labels, resource);
   SetValue(values, boundaries, counts, &metric);
 }
 
 /**
  * Set labels to metric data
  */
 void PrometheusExporterUtils::SetMetricBasic(prometheus_client::ClientMetric &metric,
-                                             const metric_sdk::PointAttributes &labels)
+                                             const metric_sdk::PointAttributes &labels,
+                                             const opentelemetry::sdk::resource::Resource *resource)
 {
-  if (labels.empty())
+  if (labels.empty() && nullptr == resource)
   {
     return;
   }
@@ -300,7 +366,7 @@ void PrometheusExporterUtils::SetMetricBasic(prometheus_client::ClientMetric &me
   // Note that attribute keys are sorted, but sanitized keys can be out-of-order.
   // We could sort the sanitized keys again, but this seems too expensive to do
   // in this hot code path. Instead, we ignore out-of-order keys and emit a warning.
-  metric.label.reserve(labels.size());
+  metric.label.reserve(labels.size() + 2);
   std::string previous_key;
   for (auto const &label : labels)
   {
@@ -379,7 +445,7 @@ void PrometheusExporterUtils::SetValue(std::vector<T> values,
   const auto &value_var = values[0];
   if (nostd::holds_alternative<int64_t>(value_var))
   {
-    value = nostd::get<int64_t>(value_var);
+    value = static_cast<double>(nostd::get<int64_t>(value_var));
   }
   else
   {
@@ -414,9 +480,9 @@ void PrometheusExporterUtils::SetValue(std::vector<T> values,
                                        const std::vector<uint64_t> &counts,
                                        prometheus_client::ClientMetric *metric)
 {
-  metric->histogram.sample_sum   = values[0];
-  metric->histogram.sample_count = values[1];
-  int cumulative                 = 0;
+  metric->histogram.sample_sum   = static_cast<double>(values[0]);
+  metric->histogram.sample_count = static_cast<std::uint64_t>(values[1]);
+  std::uint64_t cumulative       = 0;
   std::vector<prometheus_client::ClientMetric::Bucket> buckets;
   uint32_t idx = 0;
   for (const auto &boundary : boundaries)

exporters/prometheus/test/collector_test.cc

@@ -73,12 +73,12 @@ TEST(PrometheusCollector, BasicTests)
   MockMetricReader *reader     = new MockMetricReader();
   MockMetricProducer *producer = new MockMetricProducer();
   reader->SetMetricProducer(producer);
-  PrometheusCollector collector(reader);
+  PrometheusCollector collector(reader, true);
   auto data = collector.Collect();
 
   // Collection size should be the same as the size
   // of the records collection produced by MetricProducer.
-  ASSERT_EQ(data.size(), 1);
+  ASSERT_EQ(data.size(), 2);
   delete reader;
   delete producer;
 }