Restore TRITONSERVER_MetricObserve

include/triton/core/tritonserver.h

@@ -2648,7 +2648,7 @@ TRITONSERVER_MetricFamilyDelete(struct TRITONSERVER_MetricFamily* family);
 
 /// Get the TRITONSERVER_MetricKind of the metric family.
 ///
-/// \param metric The metric family object to query.
+/// \param family The metric family object to query.
 /// \param kind Returns the TRITONSERVER_MetricKind of metric.
 /// \return a TRITONSERVER_Error indicating success or failure.
 TRITONSERVER_DECLSPEC struct TRITONSERVER_Error*
@@ -2664,10 +2664,12 @@ TRITONSERVER_GetMetricFamilyKind(
 TRITONSERVER_DECLSPEC struct TRITONSERVER_Error* TRITONSERVER_MetricArgsNew(
     struct TRITONSERVER_MetricArgs** args);
 
-/// Set metric args with prometheus histogram metric parameter.
+/// Set metric args with histogram metric parameter.
 ///
 /// \param args The metric args object to set.
-/// \param buckets The array of bucket boundaries.
+/// \param buckets The array of bucket boundaries for the expected range of
+/// observed values.
+///
 /// \param buckets_count The number of bucket boundaries.
 /// \return a TRITONSERVER_Error indicating success or failure.
 TRITONSERVER_DECLSPEC struct TRITONSERVER_Error*
@@ -2732,10 +2734,9 @@ TRITONSERVER_DECLSPEC struct TRITONSERVER_Error* TRITONSERVER_MetricDelete(
     struct TRITONSERVER_Metric* metric);
 
 /// Get the current value of a metric object.
-/// Supports metrics of kind TRITONSERVER_METRIC_KIND_COUNTER,
-/// TRITONSERVER_METRIC_KIND_GAUGE, TRITONSERVER_METRIC_KIND_HISTOGRAM, and
-/// returns TRITONSERVER_ERROR_UNSUPPORTED for unsupported
-/// TRITONSERVER_MetricKind.
+/// Supports metrics of kind TRITONSERVER_METRIC_KIND_COUNTER
+/// and TRITONSERVER_METRIC_KIND_GAUGE, and returns
+/// TRITONSERVER_ERROR_UNSUPPORTED for unsupported TRITONSERVER_MetricKind.
 ///
 /// \param metric The metric object to query.
 /// \param value Returns the current value of the metric object.
@@ -2756,9 +2757,8 @@ TRITONSERVER_DECLSPEC struct TRITONSERVER_Error* TRITONSERVER_MetricValue(
 TRITONSERVER_DECLSPEC struct TRITONSERVER_Error* TRITONSERVER_MetricIncrement(
     struct TRITONSERVER_Metric* metric, double value);
 
-/// Set the current value of metric to value or observe the value to metric.
-/// Supports metrics of kind TRITONSERVER_METRIC_KIND_GAUGE and
-/// TRITONSERVER_METRIC_KIND_HISTOGRAM. Returns
+/// Set the current value of metric to value.
+/// Supports metrics of kind TRITONSERVER_METRIC_KIND_GAUGE and returns
 /// TRITONSERVER_ERROR_UNSUPPORTED for unsupported TRITONSERVER_MetricKind.
 ///
 /// \param metric The metric object to update.
@@ -2767,6 +2767,16 @@ TRITONSERVER_DECLSPEC struct TRITONSERVER_Error* TRITONSERVER_MetricIncrement(
 TRITONSERVER_DECLSPEC struct TRITONSERVER_Error* TRITONSERVER_MetricSet(
     struct TRITONSERVER_Metric* metric, double value);
 
+/// Sample an observation and count it to the appropriate bucket of a metric.
+/// Supports metrics of kind TRITONSERVER_METRIC_KIND_HISTOGRAM and returns
+/// TRITONSERVER_ERROR_UNSUPPORTED for unsupported TRITONSERVER_MetricKind.
+///
+/// \param metric The metric object to update.
+/// \param value The amount for metric to sample observation.
+/// \return a TRITONSERVER_Error indicating success or failure.
+TRITONSERVER_DECLSPEC struct TRITONSERVER_Error* TRITONSERVER_MetricObserve(
+    struct TRITONSERVER_Metric* metric, double value);
+
 /// Get the TRITONSERVER_MetricKind of metric of its corresponding family.
 ///
 /// \param metric The metric object to query.

src/metric_family.cc

@@ -359,6 +359,40 @@ Metric::Set(double value)
       gauge_ptr->Set(value);
       break;
     }
+    case TRITONSERVER_METRIC_KIND_HISTOGRAM: {
+      return TRITONSERVER_ErrorNew(
+          TRITONSERVER_ERROR_UNSUPPORTED,
+          "TRITONSERVER_METRIC_KIND_HISTOGRAM does not support Set");
+    }
+    default:
+      return TRITONSERVER_ErrorNew(
+          TRITONSERVER_ERROR_UNSUPPORTED,
+          "Unsupported TRITONSERVER_MetricKind");
+  }
+
+  return nullptr;  // Success
+}
+
+TRITONSERVER_Error*
+Metric::Observe(double value)
+{
+  if (metric_ == nullptr) {
+    return TRITONSERVER_ErrorNew(
+        TRITONSERVER_ERROR_INTERNAL,
+        "Could not set metric value. Metric has been invalidated.");
+  }
+
+  switch (kind_) {
+    case TRITONSERVER_METRIC_KIND_COUNTER: {
+      return TRITONSERVER_ErrorNew(
+          TRITONSERVER_ERROR_UNSUPPORTED,
+          "TRITONSERVER_METRIC_KIND_COUNTER does not support Observe");
+    }
+    case TRITONSERVER_METRIC_KIND_GAUGE: {
+      return TRITONSERVER_ErrorNew(
+          TRITONSERVER_ERROR_UNSUPPORTED,
+          "TRITONSERVER_METRIC_KIND_GAUGE does not support Observe");
+    }
     case TRITONSERVER_METRIC_KIND_HISTOGRAM: {
       auto histogram_ptr = reinterpret_cast<prometheus::Histogram*>(metric_);
       histogram_ptr->Observe(value);

src/test/metrics_api_test.cc

@@ -244,7 +244,7 @@ HistogramAPIHelper(
   double sum = 0.0;
   for (auto datum : data) {
     FAIL_TEST_IF_ERR(
-        TRITONSERVER_MetricSet(metric, datum), "observe metric value");
+        TRITONSERVER_MetricObserve(metric, datum), "observe metric value");
     sum += datum;
   }
   std::vector<std::uint64_t> cumulative_counts = {1, 1, 2, 2, 3, 3};

src/tritonserver.cc

@@ -3525,6 +3525,17 @@ TRITONSERVER_MetricSet(TRITONSERVER_Metric* metric, double value)
 #endif  // TRITON_ENABLE_METRICS
 }
 
+TRITONSERVER_Error*
+TRITONSERVER_MetricObserve(TRITONSERVER_Metric* metric, double value)
+{
+#ifdef TRITON_ENABLE_METRICS
+  return reinterpret_cast<tc::Metric*>(metric)->Observe(value);
+#else
+  return TRITONSERVER_ErrorNew(
+      TRITONSERVER_ERROR_UNSUPPORTED, "metrics not supported");
+#endif  // TRITON_ENABLE_METRICS
+}
+
 TRITONSERVER_Error*
 TRITONSERVER_GetMetricKind(
     TRITONSERVER_Metric* metric, TRITONSERVER_MetricKind* kind)

src/tritonserver_stub.cc

@@ -1105,6 +1105,11 @@ TRITONSERVER_MetricSet()
 {
 }
 
+TRITONAPI_DECLSPEC void
+TRITONSERVER_MetricObserve()
+{
+}
+
 TRITONAPI_DECLSPEC void
 TRITONSERVER_GetMetricKind()
 {