Move RuntimeChannel type arg T to associated types (#1314)

RuntimeChannel::batch_message_channel needs to be generic over the
message type. The type used to be declared on the RuntimeChannel<T>
trait. This means a RuntimeChannel can only be used with one particular
message type, which feels unfortunate.

    fn install<R: RuntimeChannel<??::BatchMessage>>(runtime: R) {
        // Can't use the same runtime here. :-(
	TracerProvider::builder().with_batch_exporter(e, runtime);
	LoggerProvider::builder().with_batch_exporter(e, runtime);
    }

This change moves the type argument to the batch_message_channel<T>
function and the associated types Receiver<T> and Sender<T>. Channels
are still specific to a message type, but a RuntimeChannel can be used
with any number of message types.

    fn install<R: RuntimeChannel>(runtime: R) {
        // It works. :-)
	TracerProvider::builder().with_batch_exporter(e, runtime);
	LoggerProvider::builder().with_batch_exporter(e, runtime);
    }

This also means the BatchMessage types no longer need to be public.

opentelemetry-contrib/src/trace/exporter/jaeger_json.rs

@@ -8,7 +8,7 @@ use opentelemetry::trace::{SpanId, TraceError};
 use opentelemetry_sdk::{
     export::trace::{ExportResult, SpanData, SpanExporter},
     runtime::RuntimeChannel,
-    trace::{BatchMessage, Tracer, TracerProvider},
+    trace::{Tracer, TracerProvider},
 };
 use opentelemetry_semantic_conventions::SCHEMA_URL;
 use std::collections::HashMap;
@@ -213,7 +213,7 @@ fn opentelemetry_value_to_json(value: &opentelemetry::Value) -> (&str, serde_jso
 ///
 /// [`RuntimeChannel`]: opentelemetry_sdk::runtime::RuntimeChannel
 #[async_trait]
-pub trait JaegerJsonRuntime: RuntimeChannel<BatchMessage> + std::fmt::Debug {
+pub trait JaegerJsonRuntime: RuntimeChannel + std::fmt::Debug {
     /// Create a new directory if the given path does not exist yet
     async fn create_dir(&self, path: &Path) -> ExportResult;
     /// Write the provided content to a new file at the given path

opentelemetry-datadog/src/exporter/mod.rs

@@ -15,7 +15,7 @@ use opentelemetry_sdk::{
     export::trace::{ExportResult, SpanData, SpanExporter},
     resource::{ResourceDetector, SdkProvidedResourceDetector},
     runtime::RuntimeChannel,
-    trace::{BatchMessage, Config, Tracer, TracerProvider},
+    trace::{Config, Tracer, TracerProvider},
     Resource,
 };
 use opentelemetry_semantic_conventions as semcov;
@@ -300,10 +300,7 @@ impl DatadogPipelineBuilder {
 
     /// Install the Datadog trace exporter pipeline using a batch span processor with the specified
     /// runtime.
-    pub fn install_batch<R: RuntimeChannel<BatchMessage>>(
-        mut self,
-        runtime: R,
-    ) -> Result<Tracer, TraceError> {
+    pub fn install_batch<R: RuntimeChannel>(mut self, runtime: R) -> Result<Tracer, TraceError> {
         let (config, service_name) = self.build_config_and_service_name();
         let exporter = self.build_exporter_with_service_name(service_name)?;
         let mut provider_builder = TracerProvider::builder().with_batch_exporter(exporter, runtime);

opentelemetry-jaeger/src/exporter/runtime.rs

@@ -5,14 +5,14 @@
 ))]
 use crate::exporter::addrs_and_family;
 use async_trait::async_trait;
-use opentelemetry_sdk::{runtime::RuntimeChannel, trace::BatchMessage};
+use opentelemetry_sdk::runtime::RuntimeChannel;
 use std::net::ToSocketAddrs;
 
 /// Jaeger Trace Runtime is an extension to [`RuntimeChannel`].
 ///
 /// [`RuntimeChannel`]: opentelemetry_sdk::runtime::RuntimeChannel
 #[async_trait]
-pub trait JaegerTraceRuntime: RuntimeChannel<BatchMessage> + std::fmt::Debug {
+pub trait JaegerTraceRuntime: RuntimeChannel + std::fmt::Debug {
     /// A communication socket between Jaeger client and agent.
     type Socket: std::fmt::Debug + Send + Sync;
 

opentelemetry-otlp/src/logs.rs

@@ -19,7 +19,7 @@ use opentelemetry::{
     global,
     logs::{LogError, LoggerProvider},
 };
-use opentelemetry_sdk::{self, export::logs::LogData, logs::BatchMessage, runtime::RuntimeChannel};
+use opentelemetry_sdk::{self, export::logs::LogData, runtime::RuntimeChannel};
 
 /// Compression algorithm to use, defaults to none.
 pub const OTEL_EXPORTER_OTLP_LOGS_COMPRESSION: &str = "OTEL_EXPORTER_OTLP_LOGS_COMPRESSION";
@@ -166,7 +166,7 @@ impl OtlpLogPipeline<LogExporterBuilder> {
     /// Returns a [`Logger`] with the name `opentelemetry-otlp` and the current crate version.
     ///
     /// [`Logger`]: opentelemetry_sdk::logs::Logger
-    pub fn install_batch<R: RuntimeChannel<BatchMessage>>(
+    pub fn install_batch<R: RuntimeChannel>(
         self,
         runtime: R,
     ) -> Result<opentelemetry_sdk::logs::Logger, LogError> {
@@ -198,7 +198,7 @@ fn build_simple_with_exporter(
     logger
 }
 
-fn build_batch_with_exporter<R: RuntimeChannel<BatchMessage>>(
+fn build_batch_with_exporter<R: RuntimeChannel>(
     exporter: LogExporter,
     log_config: Option<opentelemetry_sdk::logs::Config>,
     runtime: R,

opentelemetry-otlp/src/span.rs

@@ -12,7 +12,6 @@ use opentelemetry::{
 use opentelemetry_sdk::{
     self as sdk,
     export::trace::{ExportResult, SpanData},
-    trace::BatchMessage,
 };
 use opentelemetry_semantic_conventions::SCHEMA_URL;
 use sdk::runtime::RuntimeChannel;
@@ -122,7 +121,7 @@ impl OtlpTracePipeline<SpanExporterBuilder> {
     /// `install_batch` will panic if not called within a tokio runtime
     ///
     /// [`Tracer`]: opentelemetry::trace::Tracer
-    pub fn install_batch<R: RuntimeChannel<BatchMessage>>(
+    pub fn install_batch<R: RuntimeChannel>(
         self,
         runtime: R,
     ) -> Result<sdk::trace::Tracer, TraceError> {
@@ -154,7 +153,7 @@ fn build_simple_with_exporter(
     tracer
 }
 
-fn build_batch_with_exporter<R: RuntimeChannel<BatchMessage>>(
+fn build_batch_with_exporter<R: RuntimeChannel>(
     exporter: SpanExporter,
     trace_config: Option<sdk::trace::Config>,
     runtime: R,

opentelemetry-sdk/CHANGELOG.md

@@ -52,10 +52,12 @@
 
   `should_sample` changes `attributes` from `OrderMap<Key, Value>` to
   `Vec<KeyValue>`.
+- **Breaking** Move type argument from `RuntimeChannel<T>` to associated types [#1314](https://github.com/open-telemetry/opentelemetry-rust/pull/1314)
 
 ### Removed
 
 - Remove context from Metric force_flush [#1245](https://github.com/open-telemetry/opentelemetry-rust/pull/1245)
+- Remove `logs::BatchMessage` and `trace::BatchMessage` types [#1314](https://github.com/open-telemetry/opentelemetry-rust/pull/1314)
 
 ### Fixed
 

opentelemetry-sdk/src/logs/log_emitter.rs

@@ -1,4 +1,4 @@
-use super::{BatchLogProcessor, BatchMessage, Config, LogProcessor, SimpleLogProcessor};
+use super::{BatchLogProcessor, Config, LogProcessor, SimpleLogProcessor};
 use crate::{
     export::logs::{LogData, LogExporter},
     runtime::RuntimeChannel,
@@ -140,7 +140,7 @@ impl Builder {
     }
 
     /// The `LogExporter` setup using a default `BatchLogProcessor` that this provider should use.
-    pub fn with_batch_exporter<T: LogExporter + 'static, R: RuntimeChannel<BatchMessage>>(
+    pub fn with_batch_exporter<T: LogExporter + 'static, R: RuntimeChannel>(
         self,
         exporter: T,
         runtime: R,

opentelemetry-sdk/src/logs/log_processor.rs

@@ -109,19 +109,19 @@ impl LogProcessor for SimpleLogProcessor {
 
 /// A [`LogProcessor`] that asynchronously buffers log records and reports
 /// them at a preconfigured interval.
-pub struct BatchLogProcessor<R: RuntimeChannel<BatchMessage>> {
-    message_sender: R::Sender,
+pub struct BatchLogProcessor<R: RuntimeChannel> {
+    message_sender: R::Sender<BatchMessage>,
 }
 
-impl<R: RuntimeChannel<BatchMessage>> Debug for BatchLogProcessor<R> {
+impl<R: RuntimeChannel> Debug for BatchLogProcessor<R> {
     fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
         f.debug_struct("BatchLogProcessor")
             .field("message_sender", &self.message_sender)
             .finish()
     }
 }
 
-impl<R: RuntimeChannel<BatchMessage>> LogProcessor for BatchLogProcessor<R> {
+impl<R: RuntimeChannel> LogProcessor for BatchLogProcessor<R> {
     fn emit(&self, data: LogData) {
         let result = self.message_sender.try_send(BatchMessage::ExportLog(data));
 
@@ -158,7 +158,7 @@ impl<R: RuntimeChannel<BatchMessage>> LogProcessor for BatchLogProcessor<R> {
     }
 }
 
-impl<R: RuntimeChannel<BatchMessage>> BatchLogProcessor<R> {
+impl<R: RuntimeChannel> BatchLogProcessor<R> {
     pub(crate) fn new(mut exporter: Box<dyn LogExporter>, config: BatchConfig, runtime: R) -> Self {
         let (message_sender, message_receiver) =
             runtime.batch_message_channel(config.max_queue_size);
@@ -262,7 +262,7 @@ async fn export_with_timeout<R, E>(
     batch: Vec<LogData>,
 ) -> ExportResult
 where
-    R: RuntimeChannel<BatchMessage>,
+    R: RuntimeChannel,
     E: LogExporter + ?Sized,
 {
     if batch.is_empty() {
@@ -323,7 +323,7 @@ pub struct BatchLogProcessorBuilder<E, R> {
 impl<E, R> BatchLogProcessorBuilder<E, R>
 where
     E: LogExporter + 'static,
-    R: RuntimeChannel<BatchMessage>,
+    R: RuntimeChannel,
 {
     /// Set max queue size for batches
     pub fn with_max_queue_size(self, size: usize) -> Self {
@@ -372,7 +372,7 @@ where
 /// Messages sent between application thread and batch log processor's work thread.
 #[allow(clippy::large_enum_variant)]
 #[derive(Debug)]
-pub enum BatchMessage {
+enum BatchMessage {
     /// Export logs, usually called when the log is emitted.
     ExportLog(LogData),
     /// Flush the current buffer to the backend, it can be triggered by

opentelemetry-sdk/src/logs/mod.rs

@@ -7,6 +7,5 @@ mod log_processor;
 pub use config::{config, Config};
 pub use log_emitter::{Builder, Logger, LoggerProvider};
 pub use log_processor::{
-    BatchConfig, BatchLogProcessor, BatchLogProcessorBuilder, BatchMessage, LogProcessor,
-    SimpleLogProcessor,
+    BatchConfig, BatchLogProcessor, BatchLogProcessorBuilder, LogProcessor, SimpleLogProcessor,
 };

opentelemetry-sdk/src/runtime.rs

@@ -133,19 +133,22 @@ impl Runtime for AsyncStd {
     }
 }
 
-/// `MessageRuntime` is an extension to [`Runtime`]. Currently, it provides a
+/// `RuntimeChannel` is an extension to [`Runtime`]. Currently, it provides a
 /// channel that is used by the [log] and [span] batch processors.
 ///
 /// [log]: crate::logs::BatchLogProcessor
 /// [span]: crate::trace::BatchSpanProcessor
-pub trait RuntimeChannel<T: Debug + Send>: Runtime {
+pub trait RuntimeChannel: Runtime {
     /// A future stream to receive batch messages from channels.
-    type Receiver: Stream<Item = T> + Send;
+    type Receiver<T: Debug + Send>: Stream<Item = T> + Send;
     /// A batch messages sender that can be sent across threads safely.
-    type Sender: TrySend<Message = T> + Debug;
+    type Sender<T: Debug + Send>: TrySend<Message = T> + Debug;
 
     /// Return the sender and receiver used to send batch messages.
-    fn batch_message_channel(&self, capacity: usize) -> (Self::Sender, Self::Receiver);
+    fn batch_message_channel<T: Debug + Send>(
+        &self,
+        capacity: usize,
+    ) -> (Self::Sender<T>, Self::Receiver<T>);
 }
 
 /// Error returned by a [`TrySend`] implementation.
@@ -187,11 +190,14 @@ impl<T: Send> TrySend for tokio::sync::mpsc::Sender<T> {
 
 #[cfg(feature = "rt-tokio")]
 #[cfg_attr(docsrs, doc(cfg(feature = "rt-tokio")))]
-impl<T: Debug + Send> RuntimeChannel<T> for Tokio {
-    type Receiver = tokio_stream::wrappers::ReceiverStream<T>;
-    type Sender = tokio::sync::mpsc::Sender<T>;
-
-    fn batch_message_channel(&self, capacity: usize) -> (Self::Sender, Self::Receiver) {
+impl RuntimeChannel for Tokio {
+    type Receiver<T: Debug + Send> = tokio_stream::wrappers::ReceiverStream<T>;
+    type Sender<T: Debug + Send> = tokio::sync::mpsc::Sender<T>;
+
+    fn batch_message_channel<T: Debug + Send>(
+        &self,
+        capacity: usize,
+    ) -> (Self::Sender<T>, Self::Receiver<T>) {
         let (sender, receiver) = tokio::sync::mpsc::channel(capacity);
         (
             sender,
@@ -202,11 +208,14 @@ impl<T: Debug + Send> RuntimeChannel<T> for Tokio {
 
 #[cfg(feature = "rt-tokio-current-thread")]
 #[cfg_attr(docsrs, doc(cfg(feature = "rt-tokio-current-thread")))]
-impl<T: Debug + Send> RuntimeChannel<T> for TokioCurrentThread {
-    type Receiver = tokio_stream::wrappers::ReceiverStream<T>;
-    type Sender = tokio::sync::mpsc::Sender<T>;
-
-    fn batch_message_channel(&self, capacity: usize) -> (Self::Sender, Self::Receiver) {
+impl RuntimeChannel for TokioCurrentThread {
+    type Receiver<T: Debug + Send> = tokio_stream::wrappers::ReceiverStream<T>;
+    type Sender<T: Debug + Send> = tokio::sync::mpsc::Sender<T>;
+
+    fn batch_message_channel<T: Debug + Send>(
+        &self,
+        capacity: usize,
+    ) -> (Self::Sender<T>, Self::Receiver<T>) {
         let (sender, receiver) = tokio::sync::mpsc::channel(capacity);
         (
             sender,
@@ -229,11 +238,14 @@ impl<T: Send> TrySend for async_std::channel::Sender<T> {
 
 #[cfg(feature = "rt-async-std")]
 #[cfg_attr(docsrs, doc(cfg(feature = "rt-async-std")))]
-impl<T: Debug + Send> RuntimeChannel<T> for AsyncStd {
-    type Receiver = async_std::channel::Receiver<T>;
-    type Sender = async_std::channel::Sender<T>;
-
-    fn batch_message_channel(&self, capacity: usize) -> (Self::Sender, Self::Receiver) {
+impl RuntimeChannel for AsyncStd {
+    type Receiver<T: Debug + Send> = async_std::channel::Receiver<T>;
+    type Sender<T: Debug + Send> = async_std::channel::Sender<T>;
+
+    fn batch_message_channel<T: Debug + Send>(
+        &self,
+        capacity: usize,
+    ) -> (Self::Sender<T>, Self::Receiver<T>) {
         async_std::channel::bounded(capacity)
     }
 }

opentelemetry-sdk/src/trace/mod.rs

@@ -26,8 +26,7 @@ pub use sampler::{Sampler, ShouldSample};
 pub use span::Span;
 pub use span_limit::SpanLimits;
 pub use span_processor::{
-    BatchConfig, BatchMessage, BatchSpanProcessor, BatchSpanProcessorBuilder, SimpleSpanProcessor,
-    SpanProcessor,
+    BatchConfig, BatchSpanProcessor, BatchSpanProcessorBuilder, SimpleSpanProcessor, SpanProcessor,
 };
 pub use tracer::Tracer;
 

opentelemetry-sdk/src/trace/provider.rs

@@ -9,7 +9,7 @@
 //! not duplicate this data to avoid that different [`Tracer`] instances
 //! of the [`TracerProvider`] have different versions of these data.
 use crate::runtime::RuntimeChannel;
-use crate::trace::{BatchMessage, BatchSpanProcessor, SimpleSpanProcessor, Tracer};
+use crate::trace::{BatchSpanProcessor, SimpleSpanProcessor, Tracer};
 use crate::{export::trace::SpanExporter, trace::SpanProcessor};
 use crate::{InstrumentationLibrary, Resource};
 use once_cell::sync::OnceCell;
@@ -166,7 +166,7 @@ impl Builder {
     }
 
     /// The [`SpanExporter`] setup using a default [`BatchSpanProcessor`] that this provider should use.
-    pub fn with_batch_exporter<T: SpanExporter + 'static, R: RuntimeChannel<BatchMessage>>(
+    pub fn with_batch_exporter<T: SpanExporter + 'static, R: RuntimeChannel>(
         self,
         exporter: T,
         runtime: R,

opentelemetry-sdk/src/trace/runtime_tests.rs

@@ -6,8 +6,6 @@ use crate::export::trace::{ExportResult, SpanExporter};
 use crate::runtime;
 #[cfg(any(feature = "rt-tokio", feature = "rt-tokio-current-thread"))]
 use crate::runtime::RuntimeChannel;
-#[cfg(any(feature = "rt-tokio", feature = "rt-tokio-current-thread"))]
-use crate::trace::BatchMessage;
 use futures_util::future::BoxFuture;
 #[cfg(any(feature = "rt-tokio", feature = "rt-tokio-current-thread"))]
 use opentelemetry::global::*;
@@ -42,7 +40,7 @@ impl SpanCountExporter {
 }
 
 #[cfg(any(feature = "rt-tokio", feature = "rt-tokio-current-thread"))]
-fn build_batch_tracer_provider<R: RuntimeChannel<BatchMessage>>(
+fn build_batch_tracer_provider<R: RuntimeChannel>(
     exporter: SpanCountExporter,
     runtime: R,
 ) -> crate::trace::TracerProvider {
@@ -61,9 +59,7 @@ fn build_simple_tracer_provider(exporter: SpanCountExporter) -> crate::trace::Tr
 }
 
 #[cfg(any(feature = "rt-tokio", feature = "rt-tokio-current-thread"))]
-async fn test_set_provider_in_tokio<R: RuntimeChannel<BatchMessage>>(
-    runtime: R,
-) -> Arc<AtomicUsize> {
+async fn test_set_provider_in_tokio<R: RuntimeChannel>(runtime: R) -> Arc<AtomicUsize> {
     let exporter = SpanCountExporter::new();
     let span_count = exporter.span_count.clone();
     let _ = set_tracer_provider(build_batch_tracer_provider(exporter, runtime));

opentelemetry-sdk/src/trace/sampler.rs

@@ -156,7 +156,7 @@ impl Sampler {
     where
         C: HttpClient + 'static,
         Sampler: ShouldSample,
-        R: crate::runtime::RuntimeChannel<crate::trace::BatchMessage>,
+        R: crate::runtime::RuntimeChannel,
         Svc: Into<String>,
     {
         JaegerRemoteSamplerBuilder::new(runtime, http_client, default_sampler, service_name)