Fix: handle float value in NumberDataPoint

It's currently possible to have a `Counter` with a `Float` value, but
this fails to export because the `NumberDataPoint` is always assumed to
be an `Integer` for the purposes of ProtoBuf encoding. The `.proto` for
a `NumberDataPoint` allows for a float value in the `as_double` key, so
there should be no reason that we should not be able to support `Float`
`Counter`s.

This commit adds support for `Float` values in `NumberDataPoint`, which
in turn adds support for `Float` `Counter`s. I also updated the
documentation in the structs for both `NumberDataPoint.value` and
`HistogramDataPoint.sum` to match the expected type based on the
`.proto`.

Adds a test to confirm that the metrics_exporter handles both `Integer`
and `Float` values for a `NumberDataPoint`.

exporter/otlp-metrics/lib/opentelemetry/exporter/otlp/metrics/metrics_exporter.rb

@@ -284,13 +284,20 @@ def histogram_data_point(hdp)
           end
 
           def number_data_point(ndp)
-            Opentelemetry::Proto::Metrics::V1::NumberDataPoint.new(
+            args = {
               attributes: ndp.attributes.map { |k, v| as_otlp_key_value(k, v) },
-              as_int: ndp.value,
               start_time_unix_nano: ndp.start_time_unix_nano,
               time_unix_nano: ndp.time_unix_nano,
               exemplars: ndp.exemplars # exemplars not implemented yet from metrics sdk
-            )
+            }
+
+            if ndp.value.is_a?(Float)
+              args[:as_double] = ndp.value
+            else
+              args[:as_int] = ndp.value
+            end
+
+            Opentelemetry::Proto::Metrics::V1::NumberDataPoint.new(**args)
           end
 
           # may not need this

exporter/otlp-metrics/test/opentelemetry/exporter/otlp/metrics/metrics_exporter_test.rb

@@ -463,6 +463,23 @@
       OpenTelemetry.logger = logger
     end
 
+    it 'is able to encode NumberDataPoint with Integer or Float value' do
+      stub_request(:post, 'http://localhost:4318/v1/metrics').to_return(status: 200)
+
+      [1, 0.1234].each do |value|
+        ndp = OpenTelemetry::SDK::Metrics::Aggregation::NumberDataPoint.new
+        ndp.attributes = { 'a' => 'b' }
+        ndp.start_time_unix_nano = 0
+        ndp.time_unix_nano = 0
+        ndp.value = value
+
+        metrics_data = create_metrics_data(data_points: [ndp])
+
+        result = exporter.export([metrics_data])
+        _(result).must_equal(METRICS_SUCCESS)
+      end
+    end
+
     it 'logs rpc.Status on bad request' do
       log_stream = StringIO.new
       logger = OpenTelemetry.logger

metrics_sdk/lib/opentelemetry/sdk/metrics/aggregation/histogram_data_point.rb

@@ -14,7 +14,7 @@ module Aggregation
                                         :start_time_unix_nano,  # Integer nanoseconds since Epoch
                                         :time_unix_nano,        # Integer nanoseconds since Epoch
                                         :count,                 # Integer count is the number of values in the population. Must be non-negative.
-                                        :sum,                   # Integer sum of the values in the population. If count is zero then this field then this field must be zero
+                                        :sum,                   # Float sum of the values in the population. If count is zero then this field then this field must be zero
                                         :bucket_counts,         # optional Array[Integer] field contains the count values of histogram for each bucket.
                                         :explicit_bounds,       # Array[Float] specifies buckets with explicitly defined bounds for values.
                                         :exemplars,             # optional List of exemplars collected from measurements that were used to form the data point

metrics_sdk/lib/opentelemetry/sdk/metrics/aggregation/number_data_point.rb

@@ -11,7 +11,7 @@ module Aggregation
         NumberDataPoint = Struct.new(:attributes,            # Hash{String => String, Numeric, Boolean, Array<String, Numeric, Boolean>}
                                      :start_time_unix_nano,  # Integer nanoseconds since Epoch
                                      :time_unix_nano,        # Integer nanoseconds since Epoch
-                                     :value,                 # Integer
+                                     :value,                 # Numeric
                                      :exemplars)             # optional List of exemplars collected from measurements that were used to form the data point
       end
     end