use correct default temporality for streams based on the instrument kind

Author: tsloughter

CHANGELOG.md

@@ -7,6 +7,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## Experimental SDK
+
+### Fixes
+
+- [use correct default temporality for streams based on the instrument
+  kind](https://github.com/open-telemetry/opentelemetry-erlang/pull/713)
+
+## API
+
 ## API 1.3.0 - 2024-03-15
 
 ### Changes

apps/opentelemetry_api_experimental/src/otel_instrument.erl

@@ -20,7 +20,8 @@
 -export([new/5,
          new/7,
          is_monotonic/1,
-         temporality/1]).
+         temporality/1,
+         kind_temporality/1]).
 
 -include("otel_metrics.hrl").
 
@@ -99,15 +100,18 @@ is_monotonic(#instrument{kind=?KIND_HISTOGRAM}) ->
 is_monotonic(_) ->
     false.
 
-temporality(#instrument{kind=?KIND_COUNTER}) ->
+temporality(#instrument{kind=Kind}) ->
+    kind_temporality(Kind).
+
+kind_temporality(?KIND_COUNTER) ->
     ?TEMPORALITY_DELTA;
-temporality(#instrument{kind=?KIND_OBSERVABLE_COUNTER}) ->
+kind_temporality(?KIND_OBSERVABLE_COUNTER) ->
     ?TEMPORALITY_CUMULATIVE;
-temporality(#instrument{kind=?KIND_UPDOWN_COUNTER}) ->
+kind_temporality(?KIND_UPDOWN_COUNTER) ->
     ?TEMPORALITY_DELTA;
-temporality(#instrument{kind=?KIND_OBSERVABLE_UPDOWNCOUNTER}) ->
+kind_temporality(?KIND_OBSERVABLE_UPDOWNCOUNTER) ->
     ?TEMPORALITY_CUMULATIVE;
-temporality(#instrument{kind=?KIND_HISTOGRAM}) ->
+kind_temporality(?KIND_HISTOGRAM) ->
     ?TEMPORALITY_DELTA;
-temporality(#instrument{kind=?KIND_OBSERVABLE_GAUGE}) ->
+kind_temporality(?KIND_OBSERVABLE_GAUGE) ->
     ?TEMPORALITY_CUMULATIVE.

apps/opentelemetry_experimental/src/otel_aggregation.erl

@@ -1,7 +1,8 @@
 -module(otel_aggregation).
 
 -export([maybe_init_aggregate/6,
-         default_mapping/0]).
+         default_mapping/0,
+         default_temporality_mapping/0]).
 
 -include_lib("opentelemetry_api_experimental/include/otel_metrics.hrl").
 -include("otel_view.hrl").
@@ -69,6 +70,19 @@ default_mapping() ->
       ?KIND_UPDOWN_COUNTER => otel_aggregation_sum,
       ?KIND_OBSERVABLE_UPDOWNCOUNTER => otel_aggregation_sum}.
 
+%% by default the aggregators use the same temporality as is native to the instrument
+-spec default_temporality_mapping() -> #{otel_instrument:kind() => otel_instrument:temporality()}.
+default_temporality_mapping() ->
+    lists:foldl(fun(Kind, Acc) ->
+                        Acc#{Kind => otel_instrument:kind_temporality(Kind)}
+                end, #{}, [?KIND_COUNTER,
+                           ?KIND_OBSERVABLE_COUNTER,
+                           ?KIND_HISTOGRAM,
+                           ?KIND_OBSERVABLE_GAUGE,
+                           ?KIND_UPDOWN_COUNTER,
+                           ?KIND_OBSERVABLE_UPDOWNCOUNTER
+                          ]).
+
 split(Keys, Map) ->
     lists:foldl(fun(Key, {KeptAcc, DroppedAcc}) ->
                         case maps:take(Key, DroppedAcc) of

apps/opentelemetry_experimental/src/otel_metric_reader.erl

@@ -87,7 +87,7 @@ init([ReaderId, ProviderSup, Config]) ->
     Exporter = otel_exporter:init(ExporterModuleConfig),
 
     DefaultAggregationMapping = maps:get(default_aggregation_mapping, Config, otel_aggregation:default_mapping()),
-    Temporality = maps:get(default_temporality_mapping, Config, #{}),
+    Temporality = maps:get(default_temporality_mapping, Config, otel_aggregation:default_temporality_mapping()),
 
     %% if a periodic reader is needed then this value is set
     %% somehow need to do a default of 10000 MILLIS, but only if this is a periodic reader

apps/opentelemetry_experimental/test/otel_metrics_SUITE.erl

@@ -169,8 +169,7 @@ init_per_testcase(delta_counter, Config) ->
     %% delta is the default for a counter with sum aggregation
     %% so no need to set any temporality mapping in the reader
     ok = application:set_env(opentelemetry_experimental, readers, [#{module => otel_metric_reader,
-                                                                     config => #{exporter => {otel_metric_exporter_pid, self()},
-                                                                                 default_temporality_mapping => default_temporality_mapping()}}]),
+                                                                     config => #{exporter => {otel_metric_exporter_pid, self()}}}]),
 
     {ok, _} = application:ensure_all_started(opentelemetry_experimental),