Move unit into metrics module (#564)

opentelemetry/src/core.rs

@@ -260,26 +260,3 @@ impl KeyValue {
         }
     }
 }
-
-/// Units denote underlying data units tracked by `Meter`s.
-#[derive(Clone, Default, Debug, PartialEq, Hash)]
-pub struct Unit(String);
-
-impl Unit {
-    /// Create a new `Unit` from an `Into<String>`
-    pub fn new<S: Into<String>>(value: S) -> Self {
-        Unit(value.into())
-    }
-
-    /// View unit as &str
-    pub fn as_str(&self) -> &str {
-        &self.0
-    }
-}
-
-impl AsRef<str> for Unit {
-    #[inline]
-    fn as_ref(&self) -> &str {
-        self.0.as_ref()
-    }
-}

opentelemetry/src/lib.rs

@@ -232,7 +232,7 @@ pub use context::{Context, ContextGuard};
 
 mod core;
 
-pub use crate::core::{Array, Key, KeyValue, Unit, Value};
+pub use crate::core::{Array, Key, KeyValue, Value};
 
 pub mod runtime;
 

opentelemetry/src/metrics/config.rs

@@ -1,5 +1,5 @@
+use crate::metrics::Unit;
 use crate::sdk::InstrumentationLibrary;
-use crate::Unit;
 
 /// Config contains some options for metrics of any kind.
 #[derive(Clone, Debug, PartialEq, Hash)]

opentelemetry/src/metrics/counter.rs

@@ -1,9 +1,9 @@
 use crate::{
     metrics::{
         sync_instrument::{SyncBoundInstrument, SyncInstrument},
-        Descriptor, InstrumentKind, Measurement, Meter, Number, NumberKind, Result,
+        Descriptor, InstrumentKind, Measurement, Meter, Number, NumberKind, Result, Unit,
     },
-    KeyValue, Unit,
+    KeyValue,
 };
 use std::marker;
 

opentelemetry/src/metrics/mod.rs

@@ -1,5 +1,6 @@
 //! # OpenTelemetry Metrics API
 
+use std::borrow::Cow;
 use std::result;
 use std::sync::PoisonError;
 use thiserror::Error;
@@ -85,3 +86,29 @@ impl<T> From<PoisonError<T>> for MetricsError {
         MetricsError::Other(err.to_string())
     }
 }
+
+/// Units denote underlying data units tracked by `Meter`s.
+#[derive(Clone, Default, Debug, PartialEq, Hash)]
+pub struct Unit(Cow<'static, str>);
+
+impl Unit {
+    /// Create a new `Unit` from an `Into<String>`
+    pub fn new<S>(value: S) -> Self
+    where
+        S: Into<Cow<'static, str>>,
+    {
+        Unit(value.into())
+    }
+
+    /// View unit as &str
+    pub fn as_str(&self) -> &str {
+        self.0.as_ref()
+    }
+}
+
+impl AsRef<str> for Unit {
+    #[inline]
+    fn as_ref(&self) -> &str {
+        self.0.as_ref()
+    }
+}

opentelemetry/src/metrics/observer.rs

@@ -1,8 +1,7 @@
 use crate::metrics::{
     sdk_api, AsyncRunner, Descriptor, InstrumentKind, Meter, Number, NumberKind, Observation,
-    Result,
+    Result, Unit,
 };
-use crate::Unit;
 use std::sync::Arc;
 
 /// An Observer callback that can report observations for multiple instruments.

opentelemetry/src/metrics/up_down_counter.rs

@@ -1,9 +1,9 @@
 use crate::{
     metrics::{
         sync_instrument::{SyncBoundInstrument, SyncInstrument},
-        Descriptor, InstrumentKind, Measurement, Meter, Number, NumberKind, Result,
+        Descriptor, InstrumentKind, Measurement, Meter, Number, NumberKind, Result, Unit,
     },
-    KeyValue, Unit,
+    KeyValue,
 };
 use std::marker;
 

opentelemetry/src/metrics/value_recorder.rs

@@ -1,9 +1,8 @@
 use crate::metrics::{
     sync_instrument::{SyncBoundInstrument, SyncInstrument},
-    Descriptor, InstrumentKind, Measurement, Meter, Number, NumberKind, Result,
+    Descriptor, InstrumentKind, Measurement, Meter, Number, NumberKind, Result, Unit,
 };
 use crate::KeyValue;
-use crate::Unit;
 use std::marker;
 
 /// ValueRecorder is a metric that records per-request non-additive values.