refactor: clarify why endpoints read from environment variables are not used

Author: davidB

init-tracing-opentelemetry/src/otlp/logs.rs

@@ -16,9 +16,12 @@ pub fn init_loggerprovider<F>(
 where
     F: FnOnce(LoggerProviderBuilder) -> LoggerProviderBuilder,
 {
-    let (maybe_protocol, maybe_endpoint) = read_protocol_and_endpoint_from_env();
-    let protocol = infer_protocol(maybe_protocol.as_deref(), maybe_endpoint.as_deref());
+    let protocol = {
+        let (maybe_protocol, maybe_endpoint) = read_protocol_and_endpoint_from_env();
+        infer_protocol(maybe_protocol.as_deref(), maybe_endpoint.as_deref())
+    };
 
+    // builders used the environment variables to determine the endpoint (but not to setup the protocol)
     let exporter: Option<LogExporter> = match protocol.as_deref() {
         Some("http/protobuf") => Some(LogExporter::builder().with_http().build()?),
         #[cfg(feature = "tls")]

init-tracing-opentelemetry/src/otlp/metrics.rs

@@ -21,8 +21,10 @@ pub fn init_meterprovider<F>(
 where
     F: FnOnce(MeterProviderBuilder) -> MeterProviderBuilder,
 {
-    let (maybe_protocol, maybe_endpoint) = read_protocol_and_endpoint_from_env();
-    let protocol = infer_protocol(maybe_protocol.as_deref(), maybe_endpoint.as_deref());
+    let protocol = {
+        let (maybe_protocol, maybe_endpoint) = read_protocol_and_endpoint_from_env();
+        infer_protocol(maybe_protocol.as_deref(), maybe_endpoint.as_deref())
+    };
     let timeout = env::var("OTEL_EXPORTER_OTLP_METRICS_TIMEOUT")
         .ok()
         .and_then(|var| var.parse::<u64>().ok())
@@ -43,6 +45,7 @@ where
         .and_then(|var| var.parse::<u64>().ok())
         .map_or(Duration::from_secs(60), Duration::from_millis);
 
+    // builders used the environment variables to determine the endpoint (but not to setup the protocol)
     let exporter = match protocol.as_deref() {
         Some("http/protobuf") => Some(
             MetricExporter::builder()

init-tracing-opentelemetry/src/otlp/traces.rs

@@ -18,9 +18,12 @@ where
     F: FnOnce(TracerProviderBuilder) -> TracerProviderBuilder,
 {
     debug_env();
-    let (maybe_protocol, maybe_endpoint) = read_protocol_and_endpoint_from_env();
-    let protocol = infer_protocol(maybe_protocol.as_deref(), maybe_endpoint.as_deref());
+    let protocol = {
+        let (maybe_protocol, maybe_endpoint) = read_protocol_and_endpoint_from_env();
+        infer_protocol(maybe_protocol.as_deref(), maybe_endpoint.as_deref())
+    };
 
+    // builders used the environment variables to determine the endpoint (but not to setup the protocol)
     let exporter: Option<SpanExporter> = match protocol.as_deref() {
         Some("http/protobuf") => Some(SpanExporter::builder().with_http().build()?),
         #[cfg(feature = "tls")]