Replace once_cell::Lazy with std::sync::OnceLock for global Initialization in otel-sdk crate (#2342)

Author: lalitb

opentelemetry-sdk/Cargo.toml

@@ -17,7 +17,6 @@ async-trait = { workspace = true, optional = true }
 futures-channel = "0.3"
 futures-executor = { workspace = true }
 futures-util = { workspace = true, features = ["std", "sink", "async-await-macro"] }
-once_cell = { workspace = true }
 percent-encoding = { version = "2.0", optional = true }
 rand = { workspace = true, features = ["std", "std_rng","small_rng"], optional = true }
 glob = { version = "0.3.1", optional =true}

opentelemetry-sdk/src/logs/log_emitter.rs

@@ -11,20 +11,24 @@ use std::{
     borrow::Cow,
     sync::{
         atomic::{AtomicBool, Ordering},
-        Arc,
+        Arc, OnceLock,
     },
 };
 
-use once_cell::sync::Lazy;
-
 // a no nop logger provider used as placeholder when the provider is shutdown
-static NOOP_LOGGER_PROVIDER: Lazy<LoggerProvider> = Lazy::new(|| LoggerProvider {
-    inner: Arc::new(LoggerProviderInner {
-        processors: Vec::new(),
-        resource: Resource::empty(),
-        is_shutdown: AtomicBool::new(true),
-    }),
-});
+// TODO - replace it with LazyLock once it is stable
+static NOOP_LOGGER_PROVIDER: OnceLock<LoggerProvider> = OnceLock::new();
+
+#[inline]
+fn noop_logger_provider() -> &'static LoggerProvider {
+    NOOP_LOGGER_PROVIDER.get_or_init(|| LoggerProvider {
+        inner: Arc::new(LoggerProviderInner {
+            processors: Vec::new(),
+            resource: Resource::empty(),
+            is_shutdown: AtomicBool::new(true),
+        }),
+    })
+}
 
 #[derive(Debug, Clone)]
 /// Handles the creation and coordination of [`Logger`]s.
@@ -55,7 +59,7 @@ impl opentelemetry::logs::LoggerProvider for LoggerProvider {
     fn logger_with_scope(&self, scope: InstrumentationScope) -> Self::Logger {
         // If the provider is shutdown, new logger will refer a no-op logger provider.
         if self.inner.is_shutdown.load(Ordering::Relaxed) {
-            return Logger::new(scope, NOOP_LOGGER_PROVIDER.clone());
+            return Logger::new(scope, noop_logger_provider().clone());
         }
         if scope.name().is_empty() {
             otel_info!(name: "LoggerNameEmpty",  message = "Logger name is empty; consider providing a meaningful name. Logger will function normally and the provided name will be used as-is.");

opentelemetry-sdk/src/metrics/internal/exponential_histogram.rs

@@ -1,7 +1,7 @@
 use std::{f64::consts::LOG2_E, mem::replace, ops::DerefMut, sync::Mutex, time::SystemTime};
 
-use once_cell::sync::Lazy;
 use opentelemetry::{otel_debug, KeyValue};
+use std::sync::OnceLock;
 
 use crate::metrics::{
     data::{self, Aggregation},
@@ -131,7 +131,7 @@ impl<T: Number> ExpoHistogramDataPoint<T> {
             }
             return (exp - correction) >> -self.scale;
         }
-        (exp << self.scale) + (frac.ln() * SCALE_FACTORS[self.scale as usize]) as i32 - 1
+        (exp << self.scale) + (frac.ln() * scale_factors()[self.scale as usize]) as i32 - 1
     }
 }
 
@@ -165,32 +165,38 @@ fn scale_change(max_size: i32, bin: i32, start_bin: i32, length: i32) -> u32 {
     count
 }
 
-/// Constants used in calculating the logarithm index.
-static SCALE_FACTORS: Lazy<[f64; 21]> = Lazy::new(|| {
-    [
-        LOG2_E * 2f64.powi(0),
-        LOG2_E * 2f64.powi(1),
-        LOG2_E * 2f64.powi(2),
-        LOG2_E * 2f64.powi(3),
-        LOG2_E * 2f64.powi(4),
-        LOG2_E * 2f64.powi(5),
-        LOG2_E * 2f64.powi(6),
-        LOG2_E * 2f64.powi(7),
-        LOG2_E * 2f64.powi(8),
-        LOG2_E * 2f64.powi(9),
-        LOG2_E * 2f64.powi(10),
-        LOG2_E * 2f64.powi(11),
-        LOG2_E * 2f64.powi(12),
-        LOG2_E * 2f64.powi(13),
-        LOG2_E * 2f64.powi(14),
-        LOG2_E * 2f64.powi(15),
-        LOG2_E * 2f64.powi(16),
-        LOG2_E * 2f64.powi(17),
-        LOG2_E * 2f64.powi(18),
-        LOG2_E * 2f64.powi(19),
-        LOG2_E * 2f64.powi(20),
-    ]
-});
+// TODO - replace it with LazyLock once it is stable
+static SCALE_FACTORS: OnceLock<[f64; 21]> = OnceLock::new();
+
+/// returns constants used in calculating the logarithm index.
+#[inline]
+fn scale_factors() -> &'static [f64; 21] {
+    SCALE_FACTORS.get_or_init(|| {
+        [
+            LOG2_E * 2f64.powi(0),
+            LOG2_E * 2f64.powi(1),
+            LOG2_E * 2f64.powi(2),
+            LOG2_E * 2f64.powi(3),
+            LOG2_E * 2f64.powi(4),
+            LOG2_E * 2f64.powi(5),
+            LOG2_E * 2f64.powi(6),
+            LOG2_E * 2f64.powi(7),
+            LOG2_E * 2f64.powi(8),
+            LOG2_E * 2f64.powi(9),
+            LOG2_E * 2f64.powi(10),
+            LOG2_E * 2f64.powi(11),
+            LOG2_E * 2f64.powi(12),
+            LOG2_E * 2f64.powi(13),
+            LOG2_E * 2f64.powi(14),
+            LOG2_E * 2f64.powi(15),
+            LOG2_E * 2f64.powi(16),
+            LOG2_E * 2f64.powi(17),
+            LOG2_E * 2f64.powi(18),
+            LOG2_E * 2f64.powi(19),
+            LOG2_E * 2f64.powi(20),
+        ]
+    })
+}
 
 /// Breaks the number into a normalized fraction and a base-2 exponent.
 ///

opentelemetry-sdk/src/metrics/internal/mod.rs

@@ -15,11 +15,15 @@ use std::sync::{Arc, OnceLock, RwLock};
 use aggregate::{is_under_cardinality_limit, STREAM_CARDINALITY_LIMIT};
 pub(crate) use aggregate::{AggregateBuilder, ComputeAggregation, Measure};
 pub(crate) use exponential_histogram::{EXPO_MAX_SCALE, EXPO_MIN_SCALE};
-use once_cell::sync::Lazy;
 use opentelemetry::{otel_warn, KeyValue};
 
-pub(crate) static STREAM_OVERFLOW_ATTRIBUTES: Lazy<Vec<KeyValue>> =
-    Lazy::new(|| vec![KeyValue::new("otel.metric.overflow", "true")]);
+// TODO Replace it with LazyLock once it is stable
+pub(crate) static STREAM_OVERFLOW_ATTRIBUTES: OnceLock<Vec<KeyValue>> = OnceLock::new();
+
+#[inline]
+fn stream_overflow_attributes() -> &'static Vec<KeyValue> {
+    STREAM_OVERFLOW_ATTRIBUTES.get_or_init(|| vec![KeyValue::new("otel.metric.overflow", "true")])
+}
 
 pub(crate) trait Aggregator {
     /// A static configuration that is needed in order to initialize aggregator.
@@ -134,12 +138,12 @@ where
             trackers.insert(sorted_attrs, new_tracker);
 
             self.count.fetch_add(1, Ordering::SeqCst);
-        } else if let Some(overflow_value) = trackers.get(STREAM_OVERFLOW_ATTRIBUTES.as_slice()) {
+        } else if let Some(overflow_value) = trackers.get(stream_overflow_attributes().as_slice()) {
             overflow_value.update(value);
         } else {
             let new_tracker = A::create(&self.config);
             new_tracker.update(value);
-            trackers.insert(STREAM_OVERFLOW_ATTRIBUTES.clone(), Arc::new(new_tracker));
+            trackers.insert(stream_overflow_attributes().clone(), Arc::new(new_tracker));
             otel_warn!( name: "ValueMap.measure",
                 message = "Maximum data points for metric stream exceeded. Entry added to overflow. Subsequent overflows to same metric until next collect will not be logged."
             );

opentelemetry-sdk/src/propagation/baggage.rs

@@ -1,4 +1,3 @@
-use once_cell::sync::Lazy;
 use opentelemetry::{
     baggage::{BaggageExt, KeyValueMetadata},
     otel_warn,
@@ -7,10 +6,17 @@ use opentelemetry::{
 };
 use percent_encoding::{percent_decode_str, utf8_percent_encode, AsciiSet, CONTROLS};
 use std::iter;
+use std::sync::OnceLock;
 
 static BAGGAGE_HEADER: &str = "baggage";
 const FRAGMENT: &AsciiSet = &CONTROLS.add(b' ').add(b'"').add(b';').add(b',').add(b'=');
-static BAGGAGE_FIELDS: Lazy<[String; 1]> = Lazy::new(|| [BAGGAGE_HEADER.to_owned()]);
+
+// TODO Replace this with LazyLock once it is stable.
+static BAGGAGE_FIELDS: OnceLock<[String; 1]> = OnceLock::new();
+#[inline]
+fn baggage_fields() -> &'static [String; 1] {
+    BAGGAGE_FIELDS.get_or_init(|| [BAGGAGE_HEADER.to_owned()])
+}
 
 /// Propagates name-value pairs in [W3C Baggage] format.
 ///
@@ -149,7 +155,7 @@ impl TextMapPropagator for BaggagePropagator {
     }
 
     fn fields(&self) -> FieldIter<'_> {
-        FieldIter::new(BAGGAGE_FIELDS.as_ref())
+        FieldIter::new(baggage_fields())
     }
 }
 

opentelemetry-sdk/src/propagation/trace_context.rs

@@ -1,21 +1,26 @@
 //! # W3C Trace Context Propagator
 //!
 
-use once_cell::sync::Lazy;
 use opentelemetry::{
     propagation::{text_map_propagator::FieldIter, Extractor, Injector, TextMapPropagator},
     trace::{SpanContext, SpanId, TraceContextExt, TraceFlags, TraceId, TraceState},
     Context,
 };
 use std::str::FromStr;
+use std::sync::OnceLock;
 
 const SUPPORTED_VERSION: u8 = 0;
 const MAX_VERSION: u8 = 254;
 const TRACEPARENT_HEADER: &str = "traceparent";
 const TRACESTATE_HEADER: &str = "tracestate";
 
-static TRACE_CONTEXT_HEADER_FIELDS: Lazy<[String; 2]> =
-    Lazy::new(|| [TRACEPARENT_HEADER.to_owned(), TRACESTATE_HEADER.to_owned()]);
+// TODO Replace this with LazyLock once it is stable.
+static TRACE_CONTEXT_HEADER_FIELDS: OnceLock<[String; 2]> = OnceLock::new();
+
+fn trace_context_header_fields() -> &'static [String; 2] {
+    TRACE_CONTEXT_HEADER_FIELDS
+        .get_or_init(|| [TRACEPARENT_HEADER.to_owned(), TRACESTATE_HEADER.to_owned()])
+}
 
 /// Propagates `SpanContext`s in [W3C TraceContext] format under `traceparent` and `tracestate` header.
 ///
@@ -146,7 +151,7 @@ impl TextMapPropagator for TraceContextPropagator {
     }
 
     fn fields(&self) -> FieldIter<'_> {
-        FieldIter::new(TRACE_CONTEXT_HEADER_FIELDS.as_ref())
+        FieldIter::new(trace_context_header_fields())
     }
 }
 

opentelemetry-sdk/src/trace/provider.rs

@@ -68,32 +68,38 @@ use crate::trace::{
 };
 use crate::Resource;
 use crate::{export::trace::SpanExporter, trace::SpanProcessor};
-use once_cell::sync::{Lazy, OnceCell};
 use opentelemetry::trace::TraceError;
 use opentelemetry::InstrumentationScope;
 use opentelemetry::{otel_debug, trace::TraceResult};
 use std::borrow::Cow;
 use std::sync::atomic::{AtomicBool, Ordering};
-use std::sync::Arc;
+use std::sync::{Arc, OnceLock};
 
 use super::IdGenerator;
 
-static PROVIDER_RESOURCE: OnceCell<Resource> = OnceCell::new();
+static PROVIDER_RESOURCE: OnceLock<Resource> = OnceLock::new();
 
 // a no nop tracer provider used as placeholder when the provider is shutdown
-static NOOP_TRACER_PROVIDER: Lazy<TracerProvider> = Lazy::new(|| TracerProvider {
-    inner: Arc::new(TracerProviderInner {
-        processors: Vec::new(),
-        config: Config {
-            // cannot use default here as the default resource is not empty
-            sampler: Box::new(Sampler::ParentBased(Box::new(Sampler::AlwaysOn))),
-            id_generator: Box::<RandomIdGenerator>::default(),
-            span_limits: SpanLimits::default(),
-            resource: Cow::Owned(Resource::empty()),
-        },
-        is_shutdown: AtomicBool::new(true),
-    }),
-});
+// TODO Replace with LazyLock once it is stable
+static NOOP_TRACER_PROVIDER: OnceLock<TracerProvider> = OnceLock::new();
+#[inline]
+fn noop_tracer_provider() -> &'static TracerProvider {
+    NOOP_TRACER_PROVIDER.get_or_init(|| {
+        TracerProvider {
+            inner: Arc::new(TracerProviderInner {
+                processors: Vec::new(),
+                config: Config {
+                    // cannot use default here as the default resource is not empty
+                    sampler: Box::new(Sampler::ParentBased(Box::new(Sampler::AlwaysOn))),
+                    id_generator: Box::<RandomIdGenerator>::default(),
+                    span_limits: SpanLimits::default(),
+                    resource: Cow::Owned(Resource::empty()),
+                },
+                is_shutdown: AtomicBool::new(true),
+            }),
+        }
+    })
+}
 
 /// TracerProvider inner type
 #[derive(Debug)]
@@ -269,7 +275,7 @@ impl opentelemetry::trace::TracerProvider for TracerProvider {
 
     fn tracer_with_scope(&self, scope: InstrumentationScope) -> Self::Tracer {
         if self.inner.is_shutdown.load(Ordering::Relaxed) {
-            return Tracer::new(scope, NOOP_TRACER_PROVIDER.clone());
+            return Tracer::new(scope, noop_tracer_provider().clone());
         }
         Tracer::new(scope, self.clone())
     }
@@ -392,16 +398,13 @@ impl Builder {
         // For the uncommon case where there are multiple tracer providers with different resource
         // configurations, users can optionally provide their own borrowed static resource.
         if matches!(config.resource, Cow::Owned(_)) {
-            config.resource = match PROVIDER_RESOURCE.try_insert(config.resource.into_owned()) {
-                Ok(static_resource) => Cow::Borrowed(static_resource),
-                Err((prev, new)) => {
-                    if prev == &new {
-                        Cow::Borrowed(prev)
-                    } else {
-                        Cow::Owned(new)
+            config.resource =
+                match PROVIDER_RESOURCE.get_or_init(|| config.resource.clone().into_owned()) {
+                    static_resource if *static_resource == *config.resource.as_ref() => {
+                        Cow::Borrowed(static_resource)
                     }
-                }
-            }
+                    _ => config.resource, // Use the new resource if different
+                };
         }
 
         // Create a new vector to hold the modified processors