[EXPORTER] Prometheus: Add unit to names, convert to word (#2213)

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

@@ -7,6 +7,7 @@
 #include <string>
 #include <vector>
 #include "opentelemetry/metrics/provider.h"
+#include "opentelemetry/nostd/string_view.h"
 #include "opentelemetry/sdk/metrics/meter.h"
 #include "opentelemetry/version.h"
 
@@ -35,7 +36,17 @@ class PrometheusExporterUtils
 
 private:
   /**
-   * Append key-value pair to prometheus labels.
+   * Sanitize the given metric name or label according to Prometheus rule.
+   *
+   * This function is needed because names in OpenTelemetry can contain
+   * alphanumeric characters, '_', '.', and '-', whereas in Prometheus the
+   * name should only contain alphanumeric characters and '_'.
+   * @param name name
+   */
+  static std::string SanitizeNames(std::string name);
+
+  /**
+   * Sanitize the given metric name or label according to Prometheus rule.
    *
    * @param name label name
    * @param value label value
@@ -45,6 +56,79 @@ class PrometheusExporterUtils
                                  std::string value,
                                  std::vector<::prometheus::ClientMetric::Label> *labels);
 
+  static std::string MapToPrometheusName(const std::string &name,
+                                         const std::string &unit,
+                                         ::prometheus::MetricType prometheus_type);
+
+  /**
+   * A utility function that returns the equivalent Prometheus name for the provided OTLP metric
+   * unit.
+   *
+   * @param raw_metric_unitName The raw metric unit for which Prometheus metric unit needs to be
+   *     computed.
+   * @return the computed Prometheus metric unit equivalent of the OTLP metric unit
+   */
+  static std::string GetEquivalentPrometheusUnit(const std::string &raw_metric_unitName);
+
+  /**
+   * This method retrieves the expanded Prometheus unit name for known abbreviations. OTLP metrics
+   * use the c/s notation as specified at <a href="https://ucum.org/ucum.html">UCUM</a>. The list of
+   * mappings is adopted from <a
+   * href="https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/9a9d4778bbbf242dba233db28e2fbcfda3416959/pkg/translator/prometheus/normalize_name.go#L30">OpenTelemetry
+   * Collector Contrib</a>.
+   *
+   * @param unit_abbreviation The unit that name that needs to be expanded/converted to Prometheus
+   *     units.
+   * @return The expanded/converted unit name if known, otherwise returns the input unit name as-is.
+   */
+  static std::string GetPrometheusUnit(const std::string &unit_abbreviation);
+
+  /**
+   * This method retrieves the expanded Prometheus unit name to be used with "per" units for known
+   * units. For example: s => per second (singular)
+   *
+   * @param per_unit_abbreviation The unit abbreviation used in a 'per' unit.
+   * @return The expanded unit equivalent to be used in 'per' unit if the input is a known unit,
+   *     otherwise returns the input as-is.
+   */
+  static std::string GetPrometheusPerUnit(const std::string &per_unit_abbreviation);
+
+  /**
+   * Replaces all characters that are not a letter or a digit with '_' to make the resulting string
+   * Prometheus compliant. This method also removes leading and trailing underscores - this is done
+   * to keep the resulting unit similar to what is produced from the collector's implementation.
+   *
+   * @param str The string input that needs to be made Prometheus compliant.
+   * @return the cleaned-up Prometheus compliant string.
+   */
+  static std::string CleanUpString(const std::string &str);
+
+  /**
+   * This method is used to convert the units expressed as a rate via '/' symbol in their name to
+   * their expanded text equivalent. For instance, km/h => km_per_hour. The method operates on the
+   * input by splitting it in 2 parts - before and after '/' symbol and will attempt to expand any
+   * known unit abbreviation in both parts. Unknown abbreviations & unsupported characters will
+   * remain unchanged in the final output of this function.
+   *
+   * @param rate_expressed_unit The rate unit input that needs to be converted to its text
+   * equivalent.
+   * @return The text equivalent of unit expressed as rate. If the input does not contain '/', the
+   *     function returns it as-is.
+   */
+  static std::string ConvertRateExpressedToPrometheusUnit(const std::string &rate_expressed_unit);
+
+  /**
+   * This method drops all characters enclosed within '{}' (including the curly braces) by replacing
+   * them with an empty string. Note that this method will not produce the intended effect if there
+   * are nested curly braces within the outer enclosure of '{}'.
+   *
+   * <p>For instance, {packet{s}s} => s}.
+   *
+   * @param unit The input unit from which text within curly braces needs to be removed.
+   * @return The resulting unit after removing the text within '{}'.
+   */
+  static std::string RemoveUnitPortionInBraces(const std::string &unit);
+
   static opentelemetry::sdk::metrics::AggregationType getAggregationType(
       const opentelemetry::sdk::metrics::PointType &point_type);
 
@@ -58,6 +142,7 @@ class PrometheusExporterUtils
    * Add a target_info metric to collect resource attributes
    */
   static void SetTarget(const sdk::metrics::ResourceMetrics &data,
+                        std::chrono::nanoseconds time,
                         const opentelemetry::sdk::instrumentationscope::InstrumentationScope *scope,
                         std::vector<::prometheus::MetricFamily> *output);
 
@@ -70,6 +155,7 @@ class PrometheusExporterUtils
                       const opentelemetry::sdk::metrics::PointAttributes &labels,
                       const opentelemetry::sdk::instrumentationscope::InstrumentationScope *scope,
                       ::prometheus::MetricType type,
+                      std::chrono::nanoseconds time,
                       ::prometheus::MetricFamily *metric_family,
                       const opentelemetry::sdk::resource::Resource *resource);
 
@@ -83,6 +169,7 @@ class PrometheusExporterUtils
                       const std::vector<uint64_t> &counts,
                       const opentelemetry::sdk::metrics::PointAttributes &labels,
                       const opentelemetry::sdk::instrumentationscope::InstrumentationScope *scope,
+                      std::chrono::nanoseconds time,
                       ::prometheus::MetricFamily *metric_family,
                       const opentelemetry::sdk::resource::Resource *resource);
 
@@ -92,6 +179,7 @@ class PrometheusExporterUtils
   static void SetMetricBasic(
       ::prometheus::ClientMetric &metric,
       const opentelemetry::sdk::metrics::PointAttributes &labels,
+      std::chrono::nanoseconds time,
       const opentelemetry::sdk::instrumentationscope::InstrumentationScope *scope,
       const opentelemetry::sdk::resource::Resource *resource);
 
@@ -122,6 +210,9 @@ class PrometheusExporterUtils
                        const std::vector<double> &boundaries,
                        const std::vector<uint64_t> &counts,
                        ::prometheus::ClientMetric *metric);
+
+  // For testing
+  friend class SanitizeNameTester;
 };
 }  // namespace metrics
 }  // namespace exporter