[exporter/awsemf] Drop metrics with NaN values (open-telemetry#26344)

**Description:** Metrics with NaN values for float types would cause the
EMF Exporter to error out during JSON Marshaling. This PR introduces a
change to drop metric values that contain NaN.

**Link to tracking Issue:** Fixes open-telemetry#26267 

**Testing:** Added unit tests at several different points with varying
levels of specificity. Unit tests are quite verbose in this example but
I have followed the format of existing tests while doing very little
refactoring.

**Documentation:** Update README

.chloggen/awsemf_dropnan.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: bug_fix
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: awsemfexporter
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: AWS EMF Exporter will not drop any metrics that contain NaN values to avoid JSON marshal errors.
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [26267]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [user]

exporter/awsemfexporter/README.md

@@ -20,7 +20,9 @@ and then sends them directly to CloudWatch Logs using the
 [PutLogEvents](https://docs.aws.amazon.com/AmazonCloudWatchLogs/latest/APIReference/API_PutLogEvents.html) API.
 
 ## Data Conversion
-Convert OpenTelemetry ```Int64DataPoints```, ```DoubleDataPoints```, ```SummaryDataPoints``` metrics datapoints into CloudWatch ```EMF``` structured log formats and send it to CloudWatch. Logs and Metrics will be displayed in CloudWatch console.
+Convert OpenTelemetry ```Int64DataPoints```, ```DoubleDataPoints```, ```SummaryDataPoints``` metrics datapoints into 
+CloudWatch ```EMF``` structured log formats and send it to CloudWatch. Logs and Metrics will be displayed in 
+CloudWatch console. NaN values are not supported by CloudWatch EMF and will be dropped by the exporter.
 
 ## Exporter Configuration
 

exporter/awsemfexporter/datapoint.go

@@ -61,6 +61,10 @@ type dataPoints interface {
 	// retained: indicates whether the data point is valid for further process
 	// NOTE: It is an expensive call as it calculates the metric value.
 	CalculateDeltaDatapoints(i int, instrumentationScopeName string, detailedMetrics bool, calculators *emfCalculators) (dataPoint []dataPoint, retained bool)
+	// IsStaleOrNaN returns true if metric value has NoRecordedValue flag set or if any metric value contains a NaN.
+	// When return value is true, IsStaleOrNaN also returns the attributes attached to the metric which can be used for
+	// logging purposes.
+	IsStaleOrNaN(i int) (bool, pcommon.Map)
 }
 
 // deltaMetricMetadata contains the metadata required to perform rate/delta calculation
@@ -145,6 +149,17 @@ func (dps numberDataPointSlice) CalculateDeltaDatapoints(i int, instrumentationS
 	return []dataPoint{{name: dps.metricName, value: metricVal, labels: labels, timestampMs: timestampMs}}, retained
 }
 
+func (dps numberDataPointSlice) IsStaleOrNaN(i int) (bool, pcommon.Map) {
+	metric := dps.NumberDataPointSlice.At(i)
+	if metric.Flags().NoRecordedValue() {
+		return true, metric.Attributes()
+	}
+	if metric.ValueType() == pmetric.NumberDataPointValueTypeDouble {
+		return math.IsNaN(metric.DoubleValue()), metric.Attributes()
+	}
+	return false, pcommon.Map{}
+}
+
 // CalculateDeltaDatapoints retrieves the HistogramDataPoint at the given index.
 func (dps histogramDataPointSlice) CalculateDeltaDatapoints(i int, instrumentationScopeName string, _ bool, _ *emfCalculators) ([]dataPoint, bool) {
 	metric := dps.HistogramDataPointSlice.At(i)
@@ -164,6 +179,17 @@ func (dps histogramDataPointSlice) CalculateDeltaDatapoints(i int, instrumentati
 	}}, true
 }
 
+func (dps histogramDataPointSlice) IsStaleOrNaN(i int) (bool, pcommon.Map) {
+	metric := dps.HistogramDataPointSlice.At(i)
+	if metric.Flags().NoRecordedValue() {
+		return true, metric.Attributes()
+	}
+	if math.IsNaN(metric.Max()) || math.IsNaN(metric.Sum()) || math.IsNaN(metric.Min()) {
+		return true, metric.Attributes()
+	}
+	return false, pcommon.Map{}
+}
+
 // CalculateDeltaDatapoints retrieves the ExponentialHistogramDataPoint at the given index.
 func (dps exponentialHistogramDataPointSlice) CalculateDeltaDatapoints(idx int, instrumentationScopeName string, _ bool, _ *emfCalculators) ([]dataPoint, bool) {
 	metric := dps.ExponentialHistogramDataPointSlice.At(idx)
@@ -246,6 +272,20 @@ func (dps exponentialHistogramDataPointSlice) CalculateDeltaDatapoints(idx int,
 	}}, true
 }
 
+func (dps exponentialHistogramDataPointSlice) IsStaleOrNaN(i int) (bool, pcommon.Map) {
+	metric := dps.ExponentialHistogramDataPointSlice.At(i)
+	if metric.Flags().NoRecordedValue() {
+		return true, metric.Attributes()
+	}
+	if math.IsNaN(metric.Max()) ||
+		math.IsNaN(metric.Min()) ||
+		math.IsNaN(metric.Sum()) {
+		return true, metric.Attributes()
+	}
+
+	return false, pcommon.Map{}
+}
+
 // CalculateDeltaDatapoints retrieves the SummaryDataPoint at the given index and perform calculation with sum and count while retain the quantile value.
 func (dps summaryDataPointSlice) CalculateDeltaDatapoints(i int, instrumentationScopeName string, detailedMetrics bool, calculators *emfCalculators) ([]dataPoint, bool) {
 	metric := dps.SummaryDataPointSlice.At(i)
@@ -303,6 +343,17 @@ func (dps summaryDataPointSlice) CalculateDeltaDatapoints(i int, instrumentation
 	return datapoints, retained
 }
 
+func (dps summaryDataPointSlice) IsStaleOrNaN(i int) (bool, pcommon.Map) {
+	metric := dps.SummaryDataPointSlice.At(i)
+	if metric.Flags().NoRecordedValue() {
+		return true, metric.Attributes()
+	}
+	if math.IsNaN(metric.Sum()) {
+		return true, metric.Attributes()
+	}
+	return false, metric.Attributes()
+}
+
 // createLabels converts OTel AttributesMap attributes to a map
 // and optionally adds in the OTel instrumentation library name
 func createLabels(attributes pcommon.Map, instrLibName string) map[string]string {