Add some prose to the doc

Author: fcollonval

docs/examples/metrics/reader/README.rst

@@ -5,6 +5,7 @@ These examples show how to customize the metrics that are output by the SDK usin
 
 * preferred_aggregation.py: Shows how to configure the preferred aggregation for metric instrument types.
 * preferred_temporality.py: Shows how to configure the preferred temporality for metric instrument types.
+* preferred_exemplarfilter.py: Shows how to configure the exemplar filter.
 
 The source files of these examples are available :scm_web:`here <docs/examples/metrics/reader/>`.
 

docs/examples/metrics/reader/preferred_exemplarfilter.py

@@ -17,18 +17,25 @@
 from opentelemetry.metrics import get_meter_provider, set_meter_provider
 from opentelemetry.sdk.metrics import MeterProvider
 from opentelemetry.sdk.metrics._internal.exemplar import (
-    TraceBasedExemplarFilter,
+    AlwaysOnExemplarFilter,
 )
 from opentelemetry.sdk.metrics.export import (
     ConsoleMetricExporter,
     PeriodicExportingMetricReader,
 )
 from opentelemetry.sdk.trace import TracerProvider
 
-# Create an ExemplarFilter instance (e.g., TraceBasedExemplarFilter)
-# Default available values are AlwaysOffExemplarFilter, AlwaysOnExemplarFilter
-# and TraceBasedExemplarFilter
-exemplar_filter = TraceBasedExemplarFilter()
+# Create an ExemplarFilter instance
+# Available values are AlwaysOffExemplarFilter, AlwaysOnExemplarFilter
+# and TraceBasedExemplarFilter.
+# The default value is `TraceBasedExemplarFilter`.
+#
+# You can also use the environment variable `OTEL_METRICS_EXEMPLAR_FILTER` 
+# to change the default value.
+#
+# You can also define your own filter by implementing the abstract class
+# `ExemplarFilter`
+exemplar_filter = AlwaysOnExemplarFilter()
 
 exporter = ConsoleMetricExporter()
 

docs/examples/metrics/views/README.rst

@@ -7,6 +7,7 @@ These examples show how to customize the metrics that are output by the SDK usin
 * change_name.py: Shows how to change the name of a metric.
 * limit_num_of_attrs.py: Shows how to limit the number of attributes that are output for a metric.
 * drop_metrics_from_instrument.py: Shows how to drop measurements from an instrument.
+* change_reservoir_factory.py: Shows how to use your own ``ExemplarReservoir``
 
 The source files of these examples are available :scm_web:`here <docs/examples/metrics/views/>`.
 

docs/examples/metrics/views/change_reservoir_factory.py

@@ -44,6 +44,9 @@ def custom_reservoir_factory(
     if issubclass(aggregationType, _ExplicitBucketHistogramAggregation):
         return AlignedHistogramBucketExemplarReservoir
     else:
+        # Custom reservoir must accept `**kwargs` that may set the `size` for
+        # _ExponentialBucketHistogramAggregation or the `boundaries` for
+        # _ExplicitBucketHistogramAggregation
         return lambda **kwargs: SimpleFixedSizeExemplarReservoir(
             size=10,
             **{k: v for k, v in kwargs.items() if k != "size"},