chore(opentelemetry-otlp): Make invalid combinations of transport & encoding unrepresentable

opentelemetry-otlp/CHANGELOG.md

@@ -4,6 +4,28 @@
 
 - Add partial success response handling for OTLP exporters (traces, metrics, logs) per OTLP spec. Exporters now log warnings when the server returns partial success responses with rejected items and error messages. [#865](https://github.com/open-telemetry/opentelemetry-rust/issues/865)
 - Refactor `internal-logs` feature in `opentelemetry-otlp` to reduce unnecessary dependencies[3191](https://github.com/open-telemetry/opentelemetry-rust/pull/3192)
+- **Breaking** Make invalid protocol/transport combinations unrepresentable [#3082](https://github.com/open-telemetry/opentelemetry-rust/issues/3082)
+  - Removed `protocol` field from `ExportConfig` and `with_protocol()` method from `WithExportConfig` trait
+  - Added new HTTP-specific `Protocol` enum with `HttpProtobuf` and `HttpJson` variants
+  - Added `with_protocol()` method to `WithHttpConfig` trait that accepts the HTTP-specific `Protocol` enum
+  - The `Protocol` enum is now only available and only needed when using HTTP transport
+  - This change makes invalid protocol/transport combinations (like using HTTP protocol with gRPC transport) impossible to express
+  - Migration example:
+    ```rust
+    // Before:
+    SpanExporter::builder()
+        .with_http()
+        .with_protocol(Protocol::HttpBinary)  // old Protocol from ExportConfig
+        .build()
+
+    // After:
+    use opentelemetry_otlp::Protocol; 
+
+    SpanExporter::builder()
+        .with_http()
+        .with_protocol(Protocol::HttpProtobuf)  // HTTP-specific Protocol enum
+        .build()
+    ```
 
 ## 0.31.0
 

opentelemetry-otlp/examples/basic-otlp-http/src/main.rs

@@ -4,8 +4,8 @@ use opentelemetry::{
     InstrumentationScope, KeyValue,
 };
 use opentelemetry_appender_tracing::layer::OpenTelemetryTracingBridge;
-use opentelemetry_otlp::WithExportConfig;
-use opentelemetry_otlp::{LogExporter, MetricExporter, Protocol, SpanExporter};
+use opentelemetry_otlp::{LogExporter, MetricExporter, SpanExporter};
+use opentelemetry_otlp::{Protocol, WithHttpConfig};
 use opentelemetry_sdk::Resource;
 use opentelemetry_sdk::{
     logs::SdkLoggerProvider, metrics::SdkMeterProvider, trace::SdkTracerProvider,
@@ -29,7 +29,7 @@ fn get_resource() -> Resource {
 fn init_logs() -> SdkLoggerProvider {
     let exporter = LogExporter::builder()
         .with_http()
-        .with_protocol(Protocol::HttpBinary)
+        .with_protocol(Protocol::HttpProtobuf)
         .build()
         .expect("Failed to create log exporter");
 
@@ -42,7 +42,7 @@ fn init_logs() -> SdkLoggerProvider {
 fn init_traces() -> SdkTracerProvider {
     let exporter = SpanExporter::builder()
         .with_http()
-        .with_protocol(Protocol::HttpBinary) //can be changed to `Protocol::HttpJson` to export in JSON format
+        .with_protocol(Protocol::HttpProtobuf)
         .build()
         .expect("Failed to create trace exporter");
 
@@ -55,7 +55,7 @@ fn init_traces() -> SdkTracerProvider {
 fn init_metrics() -> SdkMeterProvider {
     let exporter = MetricExporter::builder()
         .with_http()
-        .with_protocol(Protocol::HttpBinary) //can be changed to `Protocol::HttpJson` to export in JSON format
+        .with_protocol(Protocol::HttpProtobuf)
         .build()
         .expect("Failed to create metric exporter");
 

opentelemetry-otlp/src/exporter/http/logs.rs

@@ -1,5 +1,4 @@
-use super::OtlpHttpClient;
-use crate::Protocol;
+use super::{OtlpHttpClient, Protocol};
 use opentelemetry::{otel_debug, otel_warn};
 use opentelemetry_sdk::error::{OTelSdkError, OTelSdkResult};
 use opentelemetry_sdk::logs::{LogBatch, LogExporter};
@@ -51,7 +50,15 @@ fn handle_partial_success(response_body: &[u8], protocol: Protocol) {
                 return;
             }
         },
-        _ => match Message::decode(response_body) {
+        Protocol::HttpProtobuf => match Message::decode(response_body) {
+            Ok(r) => r,
+            Err(e) => {
+                otel_debug!(name: "HttpLogsClient.ResponseParseError", error = e.to_string());
+                return;
+            }
+        },
+        #[cfg(not(feature = "http-json"))]
+        Protocol::HttpJson => match Message::decode(response_body) {
             Ok(r) => r,
             Err(e) => {
                 otel_debug!(name: "HttpLogsClient.ResponseParseError", error = e.to_string());
@@ -81,15 +88,15 @@ mod tests {
         let invalid = vec![0xFF, 0xFF, 0xFF, 0xFF];
 
         // Should not panic - logs debug and returns early
-        handle_partial_success(&invalid, Protocol::HttpBinary);
+        handle_partial_success(&invalid, Protocol::HttpProtobuf);
     }
 
     #[test]
     fn test_handle_empty_response() {
         let empty = vec![];
 
         // Should not panic
-        handle_partial_success(&empty, Protocol::HttpBinary);
+        handle_partial_success(&empty, Protocol::HttpProtobuf);
     }
 
     #[cfg(feature = "http-json")]

opentelemetry-otlp/src/exporter/http/metrics.rs

@@ -1,11 +1,10 @@
 use crate::metric::MetricsClient;
-use crate::Protocol;
 use opentelemetry::{otel_debug, otel_warn};
 use opentelemetry_sdk::error::{OTelSdkError, OTelSdkResult};
 use opentelemetry_sdk::metrics::data::ResourceMetrics;
 use prost::Message;
 
-use super::OtlpHttpClient;
+use super::{OtlpHttpClient, Protocol};
 
 impl MetricsClient for OtlpHttpClient {
     async fn export(&self, metrics: &ResourceMetrics) -> OTelSdkResult {
@@ -47,7 +46,15 @@ fn handle_partial_success(response_body: &[u8], protocol: Protocol) {
                 return;
             }
         },
-        _ => match Message::decode(response_body) {
+        Protocol::HttpProtobuf => match Message::decode(response_body) {
+            Ok(r) => r,
+            Err(e) => {
+                otel_debug!(name: "HttpMetricsClient.ResponseParseError", error = e.to_string());
+                return;
+            }
+        },
+        #[cfg(not(feature = "http-json"))]
+        Protocol::HttpJson => match Message::decode(response_body) {
             Ok(r) => r,
             Err(e) => {
                 otel_debug!(name: "HttpMetricsClient.ResponseParseError", error = e.to_string());
@@ -77,15 +84,15 @@ mod tests {
         let invalid = vec![0xFF, 0xFF, 0xFF, 0xFF];
 
         // Should not panic - logs debug and returns early
-        handle_partial_success(&invalid, Protocol::HttpBinary);
+        handle_partial_success(&invalid, Protocol::HttpProtobuf);
     }
 
     #[test]
     fn test_handle_empty_response() {
         let empty = vec![];
 
         // Should not panic
-        handle_partial_success(&empty, Protocol::HttpBinary);
+        handle_partial_success(&empty, Protocol::HttpProtobuf);
     }
 
     #[cfg(feature = "http-json")]