fix: address comments

* Add ExportError in MetricsError.
It can help unify the export error among trace, metric and logging in the future.

* Merge TraceError::Other into TraceError::Boxed.
Those two seems to have a lot in common. Created a custom wrap type for string and metric those two variants.

* Remove default implement for exporter_name.
It should have used in case like http client failure. But it could also encourage ppl not implement it at all.

examples/actix-http/src/main.rs

@@ -1,17 +1,14 @@
 use actix_service::Service;
 use actix_web::middleware::Logger;
 use actix_web::{web, App, HttpServer};
+use opentelemetry::trace::TraceError;
 use opentelemetry::{global, sdk::trace as sdktrace};
 use opentelemetry::{
     trace::{FutureExt, TraceContextExt, Tracer},
     Key,
 };
-use opentelemetry::trace::TraceError;
 
-fn init_tracer() -> Result<
-    (sdktrace::Tracer, opentelemetry_jaeger::Uninstall),
-    TraceError
-> {
+fn init_tracer() -> Result<(sdktrace::Tracer, opentelemetry_jaeger::Uninstall), TraceError> {
     opentelemetry_jaeger::new_pipeline()
         .with_collector_endpoint("http://127.0.0.1:14268/api/traces")
         .with_service_name("trace-http-demo")

examples/actix-udp/src/main.rs

@@ -1,17 +1,14 @@
 use actix_service::Service;
 use actix_web::middleware::Logger;
 use actix_web::{web, App, HttpServer};
+use opentelemetry::trace::TraceError;
 use opentelemetry::{global, sdk::trace as sdktrace};
 use opentelemetry::{
     trace::{FutureExt, TraceContextExt, Tracer},
     Key,
 };
-use opentelemetry::trace::TraceError;
 
-fn init_tracer() -> Result<
-    (sdktrace::Tracer, opentelemetry_jaeger::Uninstall),
-    TraceError
-> {
+fn init_tracer() -> Result<(sdktrace::Tracer, opentelemetry_jaeger::Uninstall), TraceError> {
     opentelemetry_jaeger::new_pipeline()
         .with_agent_endpoint("localhost:6831")
         .with_service_name("trace-udp-demo")

examples/async/src/main.rs

@@ -17,6 +17,7 @@
 //!     cargo run --example async_fn
 //!
 //! [`hello_world`]: https://github.com/tokio-rs/tokio/blob/132e9f1da5965530b63554d7a1c59824c3de4e30/tokio/examples/hello_world.rs
+use opentelemetry::trace::TraceError;
 use opentelemetry::{
     global,
     sdk::trace as sdktrace,
@@ -26,7 +27,6 @@ use opentelemetry::{
 use std::{error::Error, io, net::SocketAddr};
 use tokio::io::AsyncWriteExt;
 use tokio::net::TcpStream;
-use opentelemetry::trace::TraceError;
 
 async fn connect(addr: &SocketAddr) -> io::Result<TcpStream> {
     let tracer = global::tracer("connector");
@@ -53,10 +53,7 @@ async fn run(addr: &SocketAddr) -> io::Result<usize> {
     write(&mut stream).with_context(cx).await
 }
 
-fn init_tracer() -> Result<
-    (sdktrace::Tracer, opentelemetry_jaeger::Uninstall),
-    TraceError
-> {
+fn init_tracer() -> Result<(sdktrace::Tracer, opentelemetry_jaeger::Uninstall), TraceError> {
     opentelemetry_jaeger::new_pipeline()
         .with_service_name("trace-demo")
         .install()

examples/basic-otlp/src/main.rs

@@ -1,6 +1,7 @@
 use futures::stream::{Stream, StreamExt};
 use opentelemetry::exporter;
 use opentelemetry::sdk::metrics::PushController;
+use opentelemetry::trace::TraceError;
 use opentelemetry::{
     baggage::BaggageExt,
     metrics::{self, MetricsError, ObserverResult},
@@ -10,13 +11,9 @@ use opentelemetry::{
 use opentelemetry::{global, sdk::trace as sdktrace};
 use std::error::Error;
 use std::time::Duration;
-use opentelemetry::trace::TraceError;
 
-fn init_tracer(
-) -> Result<(sdktrace::Tracer, opentelemetry_otlp::Uninstall), TraceError>
-{
-    opentelemetry_otlp::new_pipeline()
-        .install()
+fn init_tracer() -> Result<(sdktrace::Tracer, opentelemetry_otlp::Uninstall), TraceError> {
+    opentelemetry_otlp::new_pipeline().install()
 }
 
 // Skip first immediate tick from tokio, not needed for async_std.

examples/basic/src/main.rs

@@ -2,6 +2,7 @@ use futures::stream::{Stream, StreamExt};
 use opentelemetry::exporter;
 use opentelemetry::global;
 use opentelemetry::sdk::{metrics::PushController, trace as sdktrace};
+use opentelemetry::trace::TraceError;
 use opentelemetry::{
     baggage::BaggageExt,
     metrics::{self, MetricsError, ObserverResult},
@@ -10,12 +11,8 @@ use opentelemetry::{
 };
 use std::error::Error;
 use std::time::Duration;
-use opentelemetry::trace::TraceError;
 
-fn init_tracer() -> Result<
-    (sdktrace::Tracer, opentelemetry_jaeger::Uninstall),
-    TraceError,
-> {
+fn init_tracer() -> Result<(sdktrace::Tracer, opentelemetry_jaeger::Uninstall), TraceError> {
     opentelemetry_jaeger::new_pipeline()
         .with_service_name("trace-demo")
         .with_tags(vec![

examples/grpc/src/client.rs

@@ -2,19 +2,17 @@ use hello_world::greeter_client::GreeterClient;
 use hello_world::HelloRequest;
 use opentelemetry::global;
 use opentelemetry::sdk::propagation::TraceContextPropagator;
+use opentelemetry::trace::TraceError;
 use opentelemetry::{
     trace::{TraceContextExt, Tracer},
     Context, KeyValue,
 };
-use opentelemetry::trace::TraceError;
 
 pub mod hello_world {
     tonic::include_proto!("helloworld");
 }
 
-fn tracing_init(
-) -> Result<(impl Tracer, opentelemetry_jaeger::Uninstall),TraceError>
-{
+fn tracing_init() -> Result<(impl Tracer, opentelemetry_jaeger::Uninstall), TraceError> {
     global::set_text_map_propagator(TraceContextPropagator::new());
     opentelemetry_jaeger::new_pipeline()
         .with_service_name("grpc-client")

examples/grpc/src/server.rs

@@ -4,12 +4,12 @@ use hello_world::greeter_server::{Greeter, GreeterServer};
 use hello_world::{HelloReply, HelloRequest};
 use opentelemetry::global;
 use opentelemetry::sdk::propagation::TraceContextPropagator;
+use opentelemetry::trace::TraceError;
 use opentelemetry::{
     trace::{Span, Tracer},
     KeyValue,
 };
 use std::error::Error;
-use opentelemetry::trace::TraceError;
 
 pub mod hello_world {
     tonic::include_proto!("helloworld"); // The string specified here must match the proto package name.
@@ -37,9 +37,7 @@ impl Greeter for MyGreeter {
     }
 }
 
-fn tracing_init(
-) -> Result<(impl Tracer, opentelemetry_jaeger::Uninstall), TraceError>
-{
+fn tracing_init() -> Result<(impl Tracer, opentelemetry_jaeger::Uninstall), TraceError> {
     global::set_text_map_propagator(TraceContextPropagator::new());
     opentelemetry_jaeger::new_pipeline()
         .with_service_name("grpc-server")

opentelemetry-contrib/src/trace/exporter/datadog/model/mod.rs

@@ -1,5 +1,4 @@
-use opentelemetry::exporter::trace;
-use opentelemetry::exporter::trace::ExportError;
+use opentelemetry::exporter::{trace, ExportError};
 
 mod v03;
 mod v05;

opentelemetry-jaeger/src/lib.rs

@@ -194,7 +194,8 @@ use agent::AgentAsyncClientUDP;
 use async_trait::async_trait;
 #[cfg(any(feature = "collector_client", feature = "wasm_collector_client"))]
 use collector::CollectorAsyncClientHttp;
-use opentelemetry::exporter::trace::ExportError;
+use opentelemetry::exporter::ExportError;
+use opentelemetry::trace::TraceError;
 use opentelemetry::{
     exporter::trace,
     global, sdk,
@@ -206,7 +207,6 @@ use std::{
     time::{Duration, SystemTime},
 };
 use uploader::BatchUploader;
-use opentelemetry::trace::TraceError;
 
 /// Default service name if no service is configured.
 const DEFAULT_SERVICE_NAME: &str = "OpenTelemetry";
@@ -417,10 +417,7 @@ impl PipelineBuilder {
     }
 
     /// Install a Jaeger pipeline with the recommended defaults.
-    pub fn install(
-        self,
-    ) -> Result<(sdk::trace::Tracer, Uninstall), TraceError>
-    {
+    pub fn install(self) -> Result<(sdk::trace::Tracer, Uninstall), TraceError> {
         let tracer_provider = self.build()?;
         let tracer =
             tracer_provider.get_tracer("opentelemetry-jaeger", Some(env!("CARGO_PKG_VERSION")));

opentelemetry-otlp/src/lib.rs

@@ -131,7 +131,7 @@ mod span;
 mod transform;
 
 pub use crate::span::{Compression, Credentials, Exporter, ExporterConfig, Protocol};
-use opentelemetry::exporter::trace::ExportError;
+use opentelemetry::exporter::ExportError;
 use opentelemetry::trace::TraceError;
 
 /// Create a new pipeline builder with the recommended configuration.

opentelemetry-zipkin/src/lib.rs

@@ -171,9 +171,14 @@ mod uploader;
 use async_trait::async_trait;
 use http::Uri;
 use model::endpoint::Endpoint;
-use opentelemetry::exporter::trace::{ExportError, HttpClient};
-use opentelemetry::trace::TraceError;
-use opentelemetry::{exporter::trace, global, sdk, trace::TracerProvider};
+use opentelemetry::{
+    exporter::{
+        trace::{self, HttpClient},
+        ExportError,
+    },
+    global, sdk,
+    trace::{TraceError, TracerProvider},
+};
 use std::net::SocketAddr;
 
 /// Default Zipkin collector endpoint

opentelemetry/src/api/metrics/mod.rs

@@ -19,6 +19,7 @@ mod sync_instrument;
 mod up_down_counter;
 mod value_recorder;
 
+use crate::exporter::ExportError;
 pub use async_instrument::{AsyncRunner, BatchObserverCallback, Observation, ObserverResult};
 pub use config::InstrumentConfig;
 pub use counter::{BoundCounter, Counter, CounterBuilder};
@@ -38,7 +39,7 @@ pub use value_recorder::{BoundValueRecorder, ValueRecorder, ValueRecorderBuilder
 pub type Result<T> = result::Result<T, MetricsError>;
 
 /// Errors returned by the metrics API.
-#[derive(Error, Debug, PartialEq)]
+#[derive(Error, Debug)]
 #[non_exhaustive]
 pub enum MetricsError {
     /// Other errors not covered by specific cases.
@@ -68,6 +69,15 @@ pub enum MetricsError {
     /// Errors when aggregator cannot subtract
     #[error("Aggregator does not subtract")]
     NoSubtraction,
+    /// Fail to export metrics
+    #[error("Export metrics failed with {0}")]
+    ExportErr(Box<dyn ExportError>),
+}
+
+impl<T: ExportError> From<T> for MetricsError {
+    fn from(err: T) -> Self {
+        MetricsError::ExportErr(Box::new(err))
+    }
 }
 
 impl<T> From<PoisonError<T>> for MetricsError {

opentelemetry/src/api/trace/mod.rs

@@ -139,7 +139,7 @@ pub use self::{
     },
     tracer::{SpanBuilder, Tracer},
 };
-use crate::exporter::trace::ExportError;
+use crate::exporter::ExportError;
 use std::time;
 
 /// Describe the result of operations in tracing API.
@@ -149,10 +149,6 @@ pub type TraceResult<T> = Result<T, TraceError>;
 #[derive(Error, Debug)]
 #[non_exhaustive]
 pub enum TraceError {
-    /// Other errors not covered by specific cases.
-    #[error("Trace error: {0}")]
-    Other(String),
-
     /// Export failed with the error returned by the exporter
     #[error("Exporting failed with {0}")]
     ExportFailed(Box<dyn ExportError>),
@@ -163,7 +159,7 @@ pub enum TraceError {
 
     /// Other errors propagated from trace SDK that weren't covered above
     #[error(transparent)]
-    Boxed(#[from] Box<dyn std::error::Error + Send + Sync + 'static>),
+    Other(#[from] Box<dyn std::error::Error + Send + Sync + 'static>),
 }
 
 impl<T> From<T> for TraceError
@@ -177,12 +173,29 @@ where
 
 impl<T> From<TrySendError<T>> for TraceError {
     fn from(err: TrySendError<T>) -> Self {
-        TraceError::Boxed(Box::new(err.into_send_error()))
+        TraceError::Other(Box::new(err.into_send_error()))
     }
 }
 
 impl From<Canceled> for TraceError {
     fn from(err: Canceled) -> Self {
-        TraceError::Boxed(Box::new(err))
+        TraceError::Other(Box::new(err))
     }
 }
+
+impl From<String> for TraceError {
+    fn from(err_msg: String) -> Self {
+        TraceError::Other(Box::new(Custom(err_msg)))
+    }
+}
+
+impl From<&'static str> for TraceError {
+    fn from(err_msg: &'static str) -> Self {
+        TraceError::Other(Box::new(Custom(err_msg.into())))
+    }
+}
+
+/// Wrap type for string
+#[derive(Error, Debug)]
+#[error("{0}")]
+struct Custom(String);

opentelemetry/src/exporter/mod.rs

@@ -14,3 +14,9 @@ pub mod metrics;
 #[cfg(feature = "trace")]
 #[cfg_attr(docsrs, doc(cfg(feature = "trace")))]
 pub mod trace;
+
+/// Marker trait for errors returned by exporters
+pub trait ExportError: std::error::Error + Send + Sync + 'static {
+    /// The name of exporter that returned this error
+    fn exporter_name(&self) -> &'static str;
+}

opentelemetry/src/exporter/trace/mod.rs

@@ -1,5 +1,6 @@
 //! Trace exporters
 use crate::api::trace::TraceError;
+use crate::exporter::ExportError;
 use crate::{
     sdk,
     trace::{Event, Link, SpanContext, SpanId, SpanKind, StatusCode},
@@ -22,14 +23,6 @@ pub mod stdout;
 /// Describes the result of an export.
 pub type ExportResult = Result<(), TraceError>;
 
-/// Marker trait for errors returned by exporters
-pub trait ExportError: std::error::Error + Send + Sync + 'static {
-    /// The name of exporter that returned this error
-    fn exporter_name(&self) -> &'static str {
-        "N/A"
-    }
-}
-
 /// `SpanExporter` defines the interface that protocol-specific exporters must
 /// implement so that they can be plugged into OpenTelemetry SDK and support
 /// sending of telemetry data.
@@ -102,7 +95,11 @@ impl std::error::Error for HttpClientError {}
 
 #[cfg(feature = "http")]
 #[cfg_attr(docsrs, doc(cfg(feature = "http")))]
-impl ExportError for HttpClientError {}
+impl ExportError for HttpClientError {
+    fn exporter_name(&self) -> &'static str {
+        "http client"
+    }
+}
 
 #[cfg(feature = "http")]
 #[cfg_attr(docsrs, doc(cfg(feature = "http")))]

opentelemetry/src/exporter/trace/stdout.rs

@@ -24,15 +24,17 @@
 //!     });
 //! }
 //! ```
-use crate::exporter::trace::ExportError;
 use crate::{
-    exporter::trace::{ExportResult, SpanData, SpanExporter},
+    exporter::{
+        trace::{ExportResult, SpanData, SpanExporter},
+        ExportError,
+    },
     global, sdk,
     trace::TracerProvider,
 };
 use async_trait::async_trait;
-use std::io::{stdout, Stdout, Write};
 use std::fmt::Debug;
+use std::io::{stdout, Stdout, Write};
 
 /// Pipeline builder
 #[derive(Debug)]