[docs] adding documentation for aggregation types (#2630)

Author: Alex Boten

docs/sdk/metrics.aggregation.rst

@@ -1,7 +1,7 @@
 opentelemetry.sdk._metrics.aggregation
-==========================================
+======================================
 
 .. automodule:: opentelemetry.sdk._metrics.aggregation
     :members:
     :undoc-members:
-    :show-inheritance:
+    :no-show-inheritance:

docs/sdk/metrics.point.rst

@@ -4,4 +4,4 @@ opentelemetry.sdk._metrics.point
 .. automodule:: opentelemetry.sdk._metrics.point
     :members:
     :undoc-members:
-    :show-inheritance:
+    :no-show-inheritance:

opentelemetry-sdk/src/opentelemetry/sdk/_metrics/aggregation.py

@@ -419,6 +419,19 @@ def _convert_aggregation_temporality(
 
 
 class ExplicitBucketHistogramAggregation(_AggregationFactory):
+    """This aggregation informs the SDK to collect:
+
+    - Count of Measurement values falling within explicit bucket boundaries.
+    - Arithmetic sum of Measurement values in population. This SHOULD NOT be collected when used with instruments that record negative measurements, e.g. UpDownCounter or ObservableGauge.
+    - Min (optional) Measurement value in population.
+    - Max (optional) Measurement value in population.
+
+
+    Args:
+        boundaries: Array of increasing values representing explicit bucket boundary values.
+        record_min_max: Whether to record min and max.
+    """
+
     def __init__(
         self,
         boundaries: Sequence[float] = (
@@ -446,6 +459,11 @@ def _create_aggregation(self, instrument: Instrument) -> _Aggregation:
 
 
 class SumAggregation(_AggregationFactory):
+    """This aggregation informs the SDK to collect:
+
+    - The arithmetic sum of Measurement values.
+    """
+
     def _create_aggregation(self, instrument: Instrument) -> _Aggregation:
 
         temporality = AggregationTemporality.UNSPECIFIED
@@ -461,6 +479,13 @@ def _create_aggregation(self, instrument: Instrument) -> _Aggregation:
 
 
 class LastValueAggregation(_AggregationFactory):
+    """
+    This aggregation informs the SDK to collect:
+
+    - The last Measurement.
+    - The timestamp of the last Measurement.
+    """
+
     def _create_aggregation(self, instrument: Instrument) -> _Aggregation:
         return _LastValueAggregation()
 

opentelemetry-sdk/src/opentelemetry/sdk/_metrics/point.py

@@ -63,7 +63,7 @@ class Metric:
     """Represents a metric point in the OpenTelemetry data model to be exported
 
     Concrete metric types contain all the information as in the OTLP proto definitions
-    (https://tinyurl.com/7h6yx24v) but are flattened as much as possible.
+    (https://github.com/open-telemetry/opentelemetry-proto/blob/b43e9b18b76abf3ee040164b55b9c355217151f3/opentelemetry/proto/metrics/v1/metrics.proto#L37) but are flattened as much as possible.
     """
 
     # common fields to all metric kinds