Incorporate histogram min and max fields into histogram language, add… (

open-telemetry#1983)

* Incorporate histogram min and max fields into histogram language, add zero bucket histogram aggregation

* Change default aggregation temporality to Delta

* Rename zero bucket histogram to degenerate histogram

* Remove monotonic parameter from histgoram aggregation, rename degenerate histogram to trivial histogram

* Adjust language on exemplar resevoir selection

* Fix type in anchor

* Remove extra line

* Remove trivial histogram aggregation

* Add RecordMinMax to Explicit Bucket Histogram

Co-authored-by: Reiley Yang <[email protected]>
Co-authored-by: Joshua MacDonald <[email protected]>

CHANGELOG.md

@@ -17,7 +17,8 @@ release.
 ### Metrics
 
 - Add optional min / max fields to histogram data model.
-  ([#1915](https://github.com/open-telemetry/opentelemetry-specification/pull/1915))
+  ([#1915](https://github.com/open-telemetry/opentelemetry-specification/pull/1915),
+  [#1983](https://github.com/open-telemetry/opentelemetry-specification/pull/1983))
 - Add exponential histogram to the metrics data model.
   ([#1935](https://github.com/open-telemetry/opentelemetry-specification/pull/1935))
 - Add clarifications on how to handle numerical limits.

specification/metrics/sdk.md

@@ -385,6 +385,7 @@ This Aggregation honors the following configuration parameters:
 | --- | --- | --- | --- |
 | Temporality | Delta, Cumulative | Cumulative | See [Temporality](./datamodel.md#temporality). |
 | Boundaries | double\[\] | [ 0, 5, 10, 25, 50, 75, 100, 250, 500, 1000 ] | Array of increasing values representing explicit bucket boundary values.<br><br>The Default Value represents the following buckets:<br>(-&infin;, 0], (0, 5.0], (5.0, 10.0], (10.0, 25.0], (25.0, 50.0], (50.0, 75.0], (75.0, 100.0], (100.0, 250.0], (250.0, 500.0], (500.0, 1000.0], (1000.0, +&infin;) |
+| RecordMinMax | true, false | true | Whether to record min and max. |
 
 Note: This aggregator should not fill out `sum` when used with instruments
 that record negative measurements, e.g. `UpDownCounter` or `ObservableGauge`.
@@ -393,6 +394,8 @@ This Aggregation informs the SDK to collect:
 
 - Count of `Measurement` values falling within explicit bucket boundaries.
 - Arithmetic sum of `Measurement` values in population.
+- Min (optional) `Measurement` value in population.
+- Max (optional) `Measurement` value in population.
 
 ## Attribute limits
 
@@ -485,9 +488,9 @@ The SDK will come with two types of built-in exemplar reservoirs:
 1. SimpleFixedSizeExemplarReservoir
 2. AlignedHistogramBucketExemplarReservoir
 
-By default, fixed sized histogram aggregators will use
-`AlignedHistogramBucketExemplarReservoir` and all other aggregaators will use
-`SimpleFixedSizeExemplarReservoir`.
+By default, explicit bucket histogram aggregators with more than 1 bucket will
+use `AlignedHistogramBucketExemplarReservoir`. All other aggregators will
+use `SimpleFixedSizeExemplarReservoir`.
 
 *SimpleExemplarReservoir*
 This Exemplar reservoir MAY take a configuration parameter for the size of