Specify a low-memory temporality preference for the OTLP metrics expo…

…rter (#2961)
open-telemetry · Dec 1, 2022 · 23214ec · 23214ec
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -15,6 +15,10 @@ release.
 
 - Define Experimental MetricProducer as a third-party provider of metric data to MetricReaders.
   ([#2951](https://github.com/open-telemetry/opentelemetry-specification/pull/2951))
+- Add OTLP exporter temporality preference named "LowMemory" which
+  configures Synchronous Counter and Histogram instruments to use
+  Delta aggregation temporality, which allows them to shed memory
+  following a cardinality explosion, thus use less memory. ([#2961](https://github.com/open-telemetry/opentelemetry-specification/pull/2961))
 
 ### Logs
 

diff --git a/specification/metrics/sdk_exporters/otlp.md b/specification/metrics/sdk_exporters/otlp.md
@@ -46,9 +46,17 @@ then by default:
 
 The recognized (case-insensitive) values for `OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE` are:
 
-* `cumulative`: Choose cumulative aggregation temporality for all instrument kinds.
-* `delta`: Choose Delta aggregation temporality for Counter, Asynchronous Counter and Histogram instrument kinds, choose
+* `Cumulative`: Choose cumulative aggregation temporality for all instrument kinds.
+* `Delta`: Choose Delta aggregation temporality for Counter, Asynchronous Counter and Histogram instrument kinds, choose
   Cumulative aggregation for UpDownCounter and Asynchronous UpDownCounter instrument kinds.
+* `LowMemory`: This configuration uses Delta aggregation temporality for Synchronous Counter and Histogram and uses Cumulative aggregation temporality for Synchronous UpDownCounter, Asynchronous Counter, and Asynchronous UpDownCounter instrument kinds.
+
+The "LowMemory" choice is so-named because the SDK can under certain
+conditions use less memory in this configuration than the others.
+Comparatively, the "cumulative" choice forces the SDK to maintain a
+delta-to-cumulative conversion for Synchronous Counter and Histogram
+instruments, while the "delta" choice forces the SDK to maintain a
+cumulative-to-delta conversion for Asynchronous Counter instruments.
 
 The recognized (case-insensitive) values for `OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION` are: