feat: Hide MetricReader and friends (open-telemetry#2928)

Author: cijothomas

opentelemetry-sdk/CHANGELOG.md

@@ -23,15 +23,22 @@ also modified to suppress telemetry before invoking exporters.
   - Fixed the overflow attribute to correctly use the boolean value `true`
     instead of the string `"true"`.
     [#2878](https://github.com/open-telemetry/opentelemetry-rust/issues/2878)
-
-- *Breaking* change for custom `MetricReader` authors.
-  The `shutdown_with_timeout` method is added to `MetricReader` trait.
-  `collect` method on `MetricReader` modified to return `OTelSdkResult`.
-  [#2905](https://github.com/open-telemetry/opentelemetry-rust/pull/2905)
 - *Breaking* `MetricError`, `MetricResult` no longer public (except when
   `spec_unstable_metrics_views` feature flag is enabled). `OTelSdkResult` should
   be used instead, wherever applicable.
+- *Breaking* change, affecting custom MetricReader authors:   The
+  `shutdown_with_timeout` method is added to `MetricReader` trait. `collect`
+  method on `MetricReader` modified to return `OTelSdkResult`.
+  [#2905](https://github.com/open-telemetry/opentelemetry-rust/pull/2905)
   [#2905](https://github.com/open-telemetry/opentelemetry-rust/pull/2905)
+- *Breaking* change, affecting custom MetricReader authors: `MetricReader`
+  trait, `ManualReader` struct, `Pipeline` struct, `InstrumentKind` enum moved
+  behind feature flag "experimental_metrics_custom_reader". These were only
+  required for writing custom readers.
+  [2928](https://github.com/open-telemetry/opentelemetry-rust/pull/2928)
+- *Breaking* `Aggregation` enum moved behind feature flag
+  "spec_unstable_metrics_views". This was only required when using Views.
+  [2928](https://github.com/open-telemetry/opentelemetry-rust/pull/2928)
 
 ## 0.29.0
 

opentelemetry-sdk/Cargo.toml

@@ -53,6 +53,7 @@ rt-tokio-current-thread = ["tokio", "tokio-stream", "experimental_async_runtime"
 internal-logs = ["opentelemetry/internal-logs"]
 experimental_metrics_periodicreader_with_async_runtime = ["metrics", "experimental_async_runtime"]
 spec_unstable_metrics_views = ["metrics"]
+experimental_metrics_custom_reader = ["metrics"]
 experimental_logs_batch_log_processor_with_async_runtime = ["logs", "experimental_async_runtime"]
 experimental_logs_concurrent_log_processor = ["logs"]
 experimental_trace_batch_span_processor_with_async_runtime = ["trace", "experimental_async_runtime"]
@@ -107,7 +108,7 @@ required-features = ["testing"]
 [[bench]]
 name = "metric"
 harness = false
-required-features = ["metrics", "spec_unstable_metrics_views"]
+required-features = ["metrics", "spec_unstable_metrics_views", "experimental_metrics_custom_reader"]
 
 [[bench]]
 name = "log"

opentelemetry-sdk/src/metrics/meter.rs

@@ -696,7 +696,7 @@ where
 mod tests {
     use std::borrow::Cow;
 
-    use crate::metrics::MetricError;
+    use crate::metrics::error::MetricError;
 
     use super::{
         validate_instrument_name, validate_instrument_unit, INSTRUMENT_NAME_EMPTY,

opentelemetry-sdk/src/metrics/meter_provider.rs

@@ -16,8 +16,8 @@ use crate::error::OTelSdkResult;
 use crate::Resource;
 
 use super::{
-    exporter::PushMetricExporter, meter::SdkMeter, noop::NoopMeter, pipeline::Pipelines,
-    reader::MetricReader, view::View, PeriodicReader,
+    exporter::PushMetricExporter, meter::SdkMeter, noop::NoopMeter,
+    periodic_reader::PeriodicReader, pipeline::Pipelines, reader::MetricReader, view::View,
 };
 
 /// Handles the creation and coordination of [Meter]s.

opentelemetry-sdk/src/metrics/mod.rs

@@ -39,12 +39,15 @@
 //!
 //! [Resource]: crate::Resource
 
+#[allow(unreachable_pub)]
+#[allow(unused)]
 pub(crate) mod aggregation;
 pub mod data;
 mod error;
 pub mod exporter;
 pub(crate) mod instrument;
 pub(crate) mod internal;
+#[cfg(feature = "experimental_metrics_custom_reader")]
 pub(crate) mod manual_reader;
 pub(crate) mod meter;
 mod meter_provider;
@@ -54,7 +57,10 @@ pub(crate) mod periodic_reader;
 /// Module for periodic reader with async runtime.
 pub mod periodic_reader_with_async_runtime;
 pub(crate) mod pipeline;
+#[cfg(feature = "experimental_metrics_custom_reader")]
 pub mod reader;
+#[cfg(not(feature = "experimental_metrics_custom_reader"))]
+pub(crate) mod reader;
 pub(crate) mod view;
 
 /// In-Memory metric exporter for testing purpose.
@@ -65,14 +71,18 @@ pub mod in_memory_exporter;
 #[cfg_attr(docsrs, doc(cfg(any(feature = "testing", test))))]
 pub use in_memory_exporter::{InMemoryMetricExporter, InMemoryMetricExporterBuilder};
 
+#[cfg(feature = "spec_unstable_metrics_views")]
 pub use aggregation::*;
 #[cfg(feature = "spec_unstable_metrics_views")]
 pub use error::{MetricError, MetricResult};
+#[cfg(feature = "experimental_metrics_custom_reader")]
 pub use manual_reader::*;
 pub use meter_provider::*;
 pub use periodic_reader::*;
+#[cfg(feature = "experimental_metrics_custom_reader")]
 pub use pipeline::Pipeline;
 
+#[cfg(feature = "experimental_metrics_custom_reader")]
 pub use instrument::InstrumentKind;
 
 #[cfg(feature = "spec_unstable_metrics_views")]

opentelemetry-sdk/src/metrics/periodic_reader.rs

@@ -17,7 +17,8 @@ use crate::{
 };
 
 use super::{
-    data::ResourceMetrics, instrument::InstrumentKind, reader::MetricReader, Pipeline, Temporality,
+    data::ResourceMetrics, instrument::InstrumentKind, pipeline::Pipeline, reader::MetricReader,
+    Temporality,
 };
 
 const DEFAULT_INTERVAL: Duration = Duration::from_secs(60);

opentelemetry-sdk/src/metrics/periodic_reader_with_async_runtime.rs

@@ -20,7 +20,9 @@ use crate::{
     Resource,
 };
 
-use super::{data::ResourceMetrics, reader::MetricReader, InstrumentKind, Pipeline};
+use super::{
+    data::ResourceMetrics, instrument::InstrumentKind, pipeline::Pipeline, reader::MetricReader,
+};
 
 const DEFAULT_TIMEOUT: Duration = Duration::from_secs(30);
 const DEFAULT_INTERVAL: Duration = Duration::from_secs(60);

opentelemetry-sdk/src/metrics/pipeline.rs

@@ -23,7 +23,7 @@ use crate::{
 
 use self::internal::AggregateFns;
 
-use super::{Aggregation, Temporality};
+use super::{aggregation::Aggregation, Temporality};
 
 /// Connects all of the instruments created by a meter provider to a [MetricReader].
 ///

opentelemetry-sdk/src/metrics/reader.rs

@@ -3,7 +3,7 @@ use crate::error::OTelSdkResult;
 use std::time::Duration;
 use std::{fmt, sync::Weak};
 
-use super::{data::ResourceMetrics, pipeline::Pipeline, InstrumentKind, Temporality};
+use super::{data::ResourceMetrics, instrument::InstrumentKind, pipeline::Pipeline, Temporality};
 
 /// The interface used between the SDK and an exporter.
 ///

opentelemetry-sdk/src/testing/metrics/metric_reader.rs

@@ -1,7 +1,7 @@
 use crate::error::{OTelSdkError, OTelSdkResult};
 use crate::metrics::Temporality;
 use crate::metrics::{
-    data::ResourceMetrics, pipeline::Pipeline, reader::MetricReader, InstrumentKind,
+    data::ResourceMetrics, instrument::InstrumentKind, pipeline::Pipeline, reader::MetricReader,
 };
 use std::sync::{Arc, Mutex, Weak};
 use std::time::Duration;

stress/Cargo.toml

@@ -52,7 +52,7 @@ ctrlc = { workspace = true }
 lazy_static = { workspace = true }
 num_cpus = { workspace = true }
 opentelemetry = { path = "../opentelemetry", features = ["metrics", "logs", "trace", "spec_unstable_logs_enabled"] }
-opentelemetry_sdk = { path = "../opentelemetry-sdk", features = ["metrics", "logs", "trace", "spec_unstable_logs_enabled", "experimental_logs_concurrent_log_processor"] }
+opentelemetry_sdk = { path = "../opentelemetry-sdk", features = ["metrics", "logs", "trace", "spec_unstable_logs_enabled", "experimental_logs_concurrent_log_processor", "experimental_metrics_custom_reader"] }
 opentelemetry-appender-tracing = { workspace = true, features = ["spec_unstable_logs_enabled"] }
 rand = { workspace = true, features = ["small_rng", "os_rng"] }
 tracing = { workspace = true, features = ["std"]}