Add .meter_provider.exemplar_filter property (#131)

* Add .meter_provider.exemplar_filter property

* Fix build

Author: jack-berg

examples/kitchen-sink.yaml

@@ -213,6 +213,8 @@ meter_provider:
           # Configure list of attribute keys to exclude from the resulting stream(s). Applies after .attribute_keys.included (i.e. excluded has higher priority than included).
           excluded:
             - key3
+  # Configure the exemplar filter. Known values include: trace_based, always_on, always_off.
+  exemplar_filter: trace_based
 
 # Configure text map context propagators.
 propagator:

examples/sdk-config.yaml

@@ -139,6 +139,8 @@ meter_provider:
             temporality_preference: cumulative
             # Configure default histogram aggregation.
             default_histogram_aggregation: explicit_bucket_histogram
+  # Configure the exemplar filter. Known values include: trace_based, always_on, always_off.
+  exemplar_filter: trace_based
 
 # Configure logger provider.
 logger_provider:

examples/sdk-migration-config.yaml

@@ -25,7 +25,6 @@
 # - OTEL_TRACES_EXPORTER
 # - OTEL_METRICS_EXPORTER
 # - OTEL_LOGS_EXPORTER
-# - OTEL_METRICS_EXEMPLAR_FILTER
 # - OTEL_EXPORTER_OTLP_PROTOCOL
 # - OTEL_EXPORTER_OTLP_ENDPOINT
 # - OTEL_EXPORTER_OTLP_INSECURE, OTEL_EXPORTER_OTLP_{SIGNAL}_INSECURE
@@ -177,6 +176,8 @@ meter_provider:
             temporality_preference: ${OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE:-cumulative}
             # Configure default histogram aggregation.
             default_histogram_aggregation: ${OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION:-explicit_bucket_histogram}
+  # Configure the exemplar filter. Known values include: trace_based, always_on, always_off.
+  exemplar_filter: ${OTEL_METRICS_EXEMPLAR_FILTER:-trace_based}
 
 # Configure logger provider.
 logger_provider:

schema/meter_provider.json

@@ -16,6 +16,14 @@
             "items": {
                 "$ref": "#/$defs/View"
             }
+        },
+        "exemplar_filter": {
+            "type": ["string", "null"],
+            "enum": [
+                "always_on",
+                "always_off",
+                "trace_based"
+            ]
         }
     },
     "$defs": {

schema/type_descriptions.yaml

@@ -203,6 +203,7 @@
   property_descriptions:
     readers: Configure metric readers.
     views: Configure views. Each view has a selector which determines the instrument(s) it applies to, and a configuration for the resulting stream(s).
+    exemplar_filter: "Configure the exemplar filter. Known values include: trace_based, always_on, always_off."
   path_patterns:
     - .meter_provider