Add OStream metrics exporter (open-telemetry#218)

exporters/ostream/BUILD

@@ -1,5 +1,28 @@
 package(default_visibility = ["//visibility:public"])
 
+cc_library(
+    name = "ostream_metrics_exporter",
+    srcs = [
+        "src/metrics_exporter.cc",
+    ],
+    hdrs = [
+        "include/opentelemetry/exporters/ostream/metrics_exporter.h",
+    ],
+    strip_include_prefix = "include",
+    deps = [
+        "//sdk/src/metrics",
+    ],
+)
+
+cc_test(
+    name = "ostream_metrics_test",
+    srcs = ["test/ostream_metrics_test.cc"],
+    deps = [
+        ":ostream_metrics_exporter",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_library(
     name = "ostream_span_exporter",
     srcs = [

exporters/ostream/CMakeLists.txt

@@ -1,10 +1,20 @@
 include_directories(include)
 
+add_library(opentelemetry_exporter_ostream_metrics src/metrics_exporter.cc)
 add_library(opentelemetry_exporter_ostream_span src/span_exporter.cc)
 
+add_executable(ostream_metrics_test test/ostream_metrics_test.cc)
 add_executable(ostream_span_test test/ostream_span_test.cc)
+
 target_link_libraries(
   ostream_span_test ${GTEST_BOTH_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT}
   opentelemetry_exporter_ostream_span)
+
+target_link_libraries(
+  ostream_metrics_test ${GTEST_BOTH_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT}
+  opentelemetry_exporter_ostream_metrics)
+
+gtest_add_tests(TARGET ostream_metrics_test TEST_PREFIX exporter. TEST_LIST
+                ostream_metrics_test)
 gtest_add_tests(TARGET ostream_span_test TEST_PREFIX exporter. TEST_LIST
                 ostream_span_test)

exporters/ostream/include/opentelemetry/exporters/ostream/metrics_exporter.h

@@ -0,0 +1,167 @@
+#pragma once
+
+#include <iostream>
+#include "opentelemetry/sdk/metrics/aggregator/exact_aggregator.h"
+#include "opentelemetry/sdk/metrics/aggregator/gauge_aggregator.h"
+#include "opentelemetry/sdk/metrics/aggregator/histogram_aggregator.h"
+#include "opentelemetry/sdk/metrics/exporter.h"
+#include "opentelemetry/sdk/metrics/record.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace sdkmetrics = opentelemetry::sdk::metrics;
+
+namespace exporter
+{
+namespace metrics
+{
+
+/**
+ * The OStreamMetricsExporter exports record data through an ostream
+ */
+class OStreamMetricsExporter final : public sdkmetrics::MetricsExporter
+{
+public:
+  /**
+   * Create an OStreamMetricsExporter. This constructor takes in a reference to an ostream that the
+   * export() function will send span data into.
+   * The default ostream is set to stdout
+   */
+  explicit OStreamMetricsExporter(std::ostream &sout = std::cout) noexcept;
+
+  sdkmetrics::ExportResult Export(const std::vector<sdkmetrics::Record> &records) noexcept override;
+
+private:
+  std::ostream &sout_;
+
+  /**
+   * Send specific data from the given AggregatorVariant based on what AggregatorKind
+   * it is holding. Each Aggregator holds data differently, so each have their own
+   * custom printing.
+   */
+  template <typename T>
+  void PrintAggregatorVariant(sdkmetrics::AggregatorVariant value)
+  {
+    auto agg     = nostd::get<std::shared_ptr<sdkmetrics::Aggregator<T>>>(value);
+    auto aggKind = agg->get_aggregator_kind();
+
+    if (!agg)
+      return;
+    switch (aggKind)
+    {
+      case sdkmetrics::AggregatorKind::Counter:
+      {
+        sout_ << "\n  sum         : " << agg->get_checkpoint()[0];
+      }
+      break;
+      case sdkmetrics::AggregatorKind::MinMaxSumCount:
+      {
+        auto mmsc = agg->get_checkpoint();
+        sout_ << "\n  min         : " << mmsc[0] << "\n  max         : " << mmsc[1]
+              << "\n  sum         : " << mmsc[2] << "\n  count       : " << mmsc[3];
+      }
+      break;
+      case sdkmetrics::AggregatorKind::Gauge:
+      {
+        auto timestamp = agg->get_checkpoint_timestamp();
+
+        sout_ << "\n  last value  : " << agg->get_checkpoint()[0]
+              << "\n  timestamp   : " << std::to_string(timestamp.time_since_epoch().count());
+      }
+      break;
+      case sdkmetrics::AggregatorKind::Exact:
+      {
+        // TODO: Find better way to print quantiles
+        if (agg->get_quant_estimation())
+        {
+          sout_ << "\n  quantiles   : "
+                << "[0: " << agg->get_quantiles(0) << ", "
+                << ".25: " << agg->get_quantiles(.25) << ", "
+                << ".50: " << agg->get_quantiles(.50) << ", "
+                << ".75: " << agg->get_quantiles(.75) << ", "
+                << "1: " << agg->get_quantiles(1) << ']';
+        }
+        else
+        {
+          auto vec = agg->get_checkpoint();
+          int size = vec.size();
+          int i    = 1;
+
+          sout_ << "\n  values      : " << '[';
+
+          for (auto val : vec)
+          {
+            sout_ << val;
+            if (i != size)
+              sout_ << ", ";
+            i++;
+          }
+          sout_ << ']';
+        }
+      }
+      break;
+      case sdkmetrics::AggregatorKind::Histogram:
+      {
+        auto boundaries = agg->get_boundaries();
+        auto counts     = agg->get_counts();
+
+        int boundaries_size = boundaries.size();
+        int counts_size     = counts.size();
+
+        sout_ << "\n  buckets     : " << '[';
+
+        for (int i = 0; i < boundaries_size; i++)
+        {
+          sout_ << boundaries[i];
+
+          if (i != boundaries_size - 1)
+            sout_ << ", ";
+        }
+        sout_ << ']';
+
+        sout_ << "\n  counts      : " << '[';
+        for (int i = 0; i < counts_size; i++)
+        {
+          sout_ << counts[i];
+
+          if (i != counts_size - 1)
+            sout_ << ", ";
+        }
+        sout_ << ']';
+      }
+      break;
+      case sdkmetrics::AggregatorKind::Sketch:
+      {
+        auto boundaries = agg->get_boundaries();
+        auto counts     = agg->get_counts();
+
+        int boundaries_size = boundaries.size();
+        int counts_size     = counts.size();
+
+        sout_ << "\n  buckets     : " << '[';
+
+        for (int i = 0; i < boundaries_size; i++)
+        {
+          sout_ << boundaries[i];
+
+          if (i != boundaries_size - 1)
+            sout_ << ", ";
+        }
+        sout_ << ']';
+
+        sout_ << "\n  counts      : " << '[';
+        for (int i = 0; i < counts_size; i++)
+        {
+          sout_ << counts[i];
+
+          if (i != counts_size - 1)
+            sout_ << ", ";
+        }
+        sout_ << ']';
+      }
+      break;
+    }
+  }
+};
+}  // namespace metrics
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE

exporters/ostream/src/metrics_exporter.cc

@@ -0,0 +1,50 @@
+#include "opentelemetry/exporters/ostream/metrics_exporter.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace metrics
+{
+
+OStreamMetricsExporter::OStreamMetricsExporter(std::ostream &sout) noexcept : sout_(sout) {}
+
+sdkmetrics::ExportResult OStreamMetricsExporter::Export(
+    const std::vector<sdk::metrics::Record> &records) noexcept
+{
+  for (auto record : records)
+  {
+    sout_ << "{"
+          << "\n  name        : " << record.GetName()
+          << "\n  description : " << record.GetDescription()
+          << "\n  labels      : " << record.GetLabels();
+
+    auto aggregator = record.GetAggregator();
+
+    /**
+     * Unpack the AggregatorVariant from the record so we can pass the data type to
+     * PrintAggregatorVariant to unpack the Aggregator from the variant.
+     */
+    if (nostd::holds_alternative<std::shared_ptr<sdkmetrics::Aggregator<int>>>(aggregator))
+    {
+      PrintAggregatorVariant<int>(aggregator);
+    }
+    else if (nostd::holds_alternative<std::shared_ptr<sdkmetrics::Aggregator<short>>>(aggregator))
+    {
+      PrintAggregatorVariant<short>(aggregator);
+    }
+    else if (nostd::holds_alternative<std::shared_ptr<sdkmetrics::Aggregator<double>>>(aggregator))
+    {
+      PrintAggregatorVariant<double>(aggregator);
+    }
+    else if (nostd::holds_alternative<std::shared_ptr<sdkmetrics::Aggregator<float>>>(aggregator))
+    {
+      PrintAggregatorVariant<float>(aggregator);
+    }
+    sout_ << "\n}\n";
+  }
+  return sdkmetrics::ExportResult::kSuccess;
+}
+
+}  // namespace metrics
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE