feat: Promote subset of Metric Views to stable

examples/metrics-advanced/Cargo.toml

@@ -13,6 +13,6 @@ bench = false
 
 [dependencies]
 opentelemetry = { path = "../../opentelemetry", features = ["metrics"] }
-opentelemetry_sdk = { path = "../../opentelemetry-sdk", features = ["spec_unstable_metrics_views"] }
+opentelemetry_sdk = { path = "../../opentelemetry-sdk" }
 opentelemetry-stdout = { workspace = true, features = ["metrics"] }
 tokio = { workspace = true, features = ["full"] }

examples/metrics-advanced/src/main.rs

@@ -1,7 +1,6 @@
 use opentelemetry::global;
-use opentelemetry::Key;
 use opentelemetry::KeyValue;
-use opentelemetry_sdk::metrics::{Aggregation, Instrument, SdkMeterProvider, Stream, Temporality};
+use opentelemetry_sdk::metrics::{Instrument, SdkMeterProvider, Stream, Temporality};
 use opentelemetry_sdk::Resource;
 use std::error::Error;
 
@@ -20,23 +19,9 @@ fn init_meter_provider() -> opentelemetry_sdk::metrics::SdkMeterProvider {
     };
 
     // for example 2
-    let my_view_drop_attributes = |i: &Instrument| {
-        if i.name == "my_counter" {
-            Some(Stream::new().allowed_attribute_keys(vec![Key::from("mykey1")]))
-        } else {
-            None
-        }
-    };
-
-    // for example 3
-    let my_view_change_aggregation = |i: &Instrument| {
+    let my_view_change_cardinality = |i: &Instrument| {
         if i.name == "my_second_histogram" {
-            Some(
-                Stream::new().aggregation(Aggregation::ExplicitBucketHistogram {
-                    boundaries: vec![0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5],
-                    record_min_max: false,
-                }),
-            )
+            Some(Stream::new().cardinality_limit(2))
         } else {
             None
         }
@@ -55,8 +40,7 @@ fn init_meter_provider() -> opentelemetry_sdk::metrics::SdkMeterProvider {
         .with_periodic_exporter(exporter)
         .with_resource(resource)
         .with_view(my_view_rename_and_unit)
-        .with_view(my_view_drop_attributes)
-        .with_view(my_view_change_aggregation)
+        .with_view(my_view_change_cardinality)
         .build();
     global::set_meter_provider(provider.clone());
     provider
@@ -88,65 +72,31 @@ async fn main() -> Result<(), Box<dyn Error + Send + Sync + 'static>> {
         ],
     );
 
-    // Example 2 - Drop unwanted attributes using view.
-    let counter = meter.u64_counter("my_counter").build();
-
-    // Record measurements using the Counter instrument.
-    // Though we are passing 4 attributes here, only 1 will be used
-    // for aggregation as view is configured to use only "mykey1"
-    // attribute.
-    counter.add(
-        10,
-        &[
-            KeyValue::new("mykey1", "myvalue1"),
-            KeyValue::new("mykey2", "myvalue2"),
-            KeyValue::new("mykey3", "myvalue3"),
-            KeyValue::new("mykey4", "myvalue4"),
-        ],
-    );
-
-    // Example 3 - Change Aggregation configuration using View.
-    // Histograms are by default aggregated using ExplicitBucketHistogram
-    // with default buckets. The configured view will change the aggregation to
-    // use a custom set of boundaries, and min/max values will not be recorded.
+    // Example 2 - Change cardinality using View.
     let histogram2 = meter
         .f64_histogram("my_second_histogram")
         .with_unit("ms")
         .with_description("My histogram example description")
         .build();
 
     // Record measurements using the histogram instrument.
-    // The values recorded are in the range of 1.2 to 1.5, warranting
-    // the change of boundaries.
-    histogram2.record(
-        1.5,
-        &[
-            KeyValue::new("mykey1", "myvalue1"),
-            KeyValue::new("mykey2", "myvalue2"),
-            KeyValue::new("mykey3", "myvalue3"),
-            KeyValue::new("mykey4", "myvalue4"),
-        ],
-    );
+    // This metric will have a cardinality limit of 2,
+    // as set in the view. Because of this, only the first two
+    // measurements will be recorded, and the rest will be folded
+    // into the overflow attribute.
+    histogram2.record(1.5, &[KeyValue::new("mykey1", "v1")]);
 
-    histogram2.record(
-        1.2,
-        &[
-            KeyValue::new("mykey1", "myvalue1"),
-            KeyValue::new("mykey2", "myvalue2"),
-            KeyValue::new("mykey3", "myvalue3"),
-            KeyValue::new("mykey4", "myvalue4"),
-        ],
-    );
+    histogram2.record(1.2, &[KeyValue::new("mykey1", "v2")]);
 
-    histogram2.record(
-        1.23,
-        &[
-            KeyValue::new("mykey1", "myvalue1"),
-            KeyValue::new("mykey2", "myvalue2"),
-            KeyValue::new("mykey3", "myvalue3"),
-            KeyValue::new("mykey4", "myvalue4"),
-        ],
-    );
+    histogram2.record(1.23, &[KeyValue::new("mykey1", "v3")]);
+
+    histogram2.record(1.4, &[KeyValue::new("mykey1", "v4")]);
+
+    histogram2.record(1.6, &[KeyValue::new("mykey1", "v5")]);
+
+    histogram2.record(1.7, &[KeyValue::new("mykey1", "v6")]);
+
+    histogram2.record(1.8, &[KeyValue::new("mykey1", "v7")]);
 
     // Metrics are exported by default every 30 seconds when using stdout exporter,
     // however shutting down the MeterProvider here instantly flushes

opentelemetry-sdk/CHANGELOG.md

@@ -43,8 +43,13 @@ also modified to suppress telemetry before invoking exporters.
   [#2928](https://github.com/open-telemetry/opentelemetry-rust/pull/2928)
 
 - TODO: Placeholder for View related changelog. Polish this after all
-  changes are done.
-  Hide public fields from `Stream` struct.
+  - The `Stream` struct now has its public fields hidden.
+  - Core view functionality is now available by default—users can change the
+    name, unit, description, and cardinality limit of a metric via views without
+    enabling the `spec_unstable_metrics_views` feature flag. Advanced view
+    features, such as custom aggregation or attribute filtering, still require
+    the `spec_unstable_metrics_views` feature.
+  - TODO: Add Stream::builder() pattern change, validation when done.
 
 - *Breaking* `Aggregation` enum moved behind feature flag
   "spec_unstable_metrics_views". This was only required when using Views.

opentelemetry-sdk/src/metrics/aggregation.rs

@@ -150,9 +150,9 @@ impl Aggregation {
 
 #[cfg(test)]
 mod tests {
+    use super::Aggregation;
     use crate::metrics::error::{MetricError, MetricResult};
     use crate::metrics::internal::{EXPO_MAX_SCALE, EXPO_MIN_SCALE};
-    use crate::metrics::Aggregation;
 
     #[test]
     fn validate_aggregation() {

opentelemetry-sdk/src/metrics/instrument.rs

@@ -83,7 +83,6 @@ impl InstrumentKind {
 /// ```
 #[derive(Clone, Default, Debug, PartialEq)]
 #[non_exhaustive]
-#[allow(unreachable_pub)]
 pub struct Instrument {
     /// The human-readable identifier of the instrument.
     pub name: Cow<'static, str>,
@@ -208,7 +207,6 @@ pub struct Stream {
     pub(crate) cardinality_limit: Option<usize>,
 }
 
-#[cfg(feature = "spec_unstable_metrics_views")]
 impl Stream {
     /// Create a new stream with empty values.
     pub fn new() -> Self {
@@ -233,12 +231,14 @@ impl Stream {
         self
     }
 
+    #[cfg(feature = "spec_unstable_metrics_views")]
     /// Set the stream aggregation.
     pub fn aggregation(mut self, aggregation: Aggregation) -> Self {
         self.aggregation = Some(aggregation);
         self
     }
 
+    #[cfg(feature = "spec_unstable_metrics_views")]
     /// Set the stream allowed attribute keys.
     ///
     /// Any attribute recorded for the stream with a key not in this set will be

opentelemetry-sdk/src/metrics/meter_provider.rs

@@ -287,7 +287,6 @@ impl MeterProviderBuilder {
         self
     }
 
-    #[cfg(feature = "spec_unstable_metrics_views")]
     /// Associates a [View] with a [MeterProvider].
     ///
     /// [View]s are appended to existing ones in a [MeterProvider] if this option is