From f0109eb98968d5d3de650bc990a9bc2d59e5b313 Mon Sep 17 00:00:00 2001
From: Ehsan Saei <71217171+esigo@users.noreply.github.com>
Date: Wed, 10 Aug 2022 21:28:54 +0200
Subject: [PATCH] Prometheus exporter support Gauge Type (#1553)

---
 exporters/prometheus/src/exporter_utils.cc    | 41 +++++++++++++++++--
 .../prometheus/test/exporter_utils_test.cc    | 31 ++++++++++++--
 2 files changed, 65 insertions(+), 7 deletions(-)

diff --git a/exporters/prometheus/src/exporter_utils.cc b/exporters/prometheus/src/exporter_utils.cc
index 80f45d823e..44f4395ece 100644
--- a/exporters/prometheus/src/exporter_utils.cc
+++ b/exporters/prometheus/src/exporter_utils.cc
@@ -5,6 +5,7 @@
 #  include <sstream>
 #  include <utility>
 #  include <vector>
+#  include "prometheus/metric_family.h"
 
 #  include <prometheus/metric_type.h>
 #  include "opentelemetry/exporters/prometheus/exporter_utils.h"
@@ -74,12 +75,38 @@ std::vector<prometheus_client::MetricFamily> PrometheusExporterUtils::TranslateT
             SetData(std::vector<double>{sum, (double)histogram_point_data.count_}, boundaries,
                     counts, point_data_attr.attributes, time, &metric_family);
           }
+          else if (type == prometheus_client::MetricType::Gauge)
+          {
+            if (nostd::holds_alternative<sdk::metrics::LastValuePointData>(
+                    point_data_attr.point_data))
+            {
+              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, time, &metric_family);
+            }
+            else
+            {
+              OTEL_INTERNAL_LOG_WARN(
+                  "[Prometheus Exporter] TranslateToPrometheus - "
+                  "invalid LastValuePointData type");
+            }
+          }
           else  // Counter, Untyped
           {
-            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, time, &metric_family);
+            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, time, &metric_family);
+            }
+            else
+            {
+              OTEL_INTERNAL_LOG_WARN(
+                  "[Prometheus Exporter] TranslateToPrometheus - "
+                  "invalid SumPointData type");
+            }
           }
         }
         output.emplace_back(metric_family);
@@ -140,6 +167,8 @@ prometheus_client::MetricType PrometheusExporterUtils::TranslateType(
       return prometheus_client::MetricType::Counter;
     case metric_sdk::AggregationType::kHistogram:
       return prometheus_client::MetricType::Histogram;
+    case metric_sdk::AggregationType::kLastValue:
+      return prometheus_client::MetricType::Gauge;
     default:
       return prometheus_client::MetricType::Untyped;
   }
@@ -276,6 +305,10 @@ void PrometheusExporterUtils::SetValue(std::vector<T> values,
       metric->counter.value = value;
       break;
     }
+    case prometheus_client::MetricType::Gauge: {
+      metric->gauge.value = value;
+      break;
+    }
     case prometheus_client::MetricType::Untyped: {
       metric->untyped.value = value;
       break;
diff --git a/exporters/prometheus/test/exporter_utils_test.cc b/exporters/prometheus/test/exporter_utils_test.cc
index cb09b27964..2f103b702b 100644
--- a/exporters/prometheus/test/exporter_utils_test.cc
+++ b/exporters/prometheus/test/exporter_utils_test.cc
@@ -43,10 +43,11 @@ void assert_basic(prometheus_client::MetricFamily &metric,
       ASSERT_EQ(buckets.size(), vals[2]);
       break;
     }
-    case prometheus_client::MetricType::Gauge:
-      // Gauge type not supported
-      ASSERT_TRUE(false);
+    case prometheus_client::MetricType::Gauge: {
+      ASSERT_DOUBLE_EQ(metric_data.gauge.value, vals[0]);
       break;
+    }
+    break;
     case prometheus_client::MetricType::Summary:
       // Summary type not supported
       ASSERT_TRUE(false);
@@ -110,6 +111,30 @@ TEST(PrometheusExporterUtils, TranslateToPrometheusIntegerCounter)
                vals);
 }
 
+TEST(PrometheusExporterUtils, TranslateToPrometheusIntegerLastValue)
+{
+  std::vector<std::unique_ptr<metric_sdk::ResourceMetrics>> collection;
+
+  collection.emplace_back(new metric_sdk::ResourceMetrics{CreateLastValuePointData()});
+
+  auto translated = PrometheusExporterUtils::TranslateToPrometheus(collection);
+  ASSERT_EQ(translated.size(), collection.size());
+
+  auto metric1          = translated[0];
+  std::vector<int> vals = {10};
+  assert_basic(metric1, "library_name", "description", prometheus_client::MetricType::Gauge, 1,
+               vals);
+
+  collection.emplace_back(new metric_sdk::ResourceMetrics{CreateLastValuePointData()});
+
+  translated = PrometheusExporterUtils::TranslateToPrometheus(collection);
+  ASSERT_EQ(translated.size(), collection.size());
+
+  auto metric2 = translated[1];
+  assert_basic(metric2, "library_name", "description", prometheus_client::MetricType::Gauge, 1,
+               vals);
+}
+
 TEST(PrometheusExporterUtils, TranslateToPrometheusHistogramNormal)
 {
   std::vector<std::unique_ptr<metric_sdk::ResourceMetrics>> collection;