add more docs

Author: gruebel

opentelemetry-otlp/CHANGELOG.md

@@ -18,10 +18,11 @@
  new one returns specific variants applicable to building an exporter. Some
  variants might be applicable only on select features.
 - **Breaking** `ExportConfig`'s `timeout` field is now optional(`Option<Duration>`)
-- **Breaking** Configuration done via code is final. ENV variables cannot be used to override the code config. Do not use code based config, if there is desire to control the settings via ENV variables.
- List of ENV variables and corresponding setting being affected by this change.
-  priority changed in favor of compile time values. Additionally the `endpoint`
-  field prioritizes compile time values over environment variables.
+- **Breaking** Export configuration done via code is final. ENV variables cannot be used to override the code config.
+  Do not use code based config, if there is desire to control the settings via ENV variables.
+  List of ENV variables and corresponding setting being affected by this change.
+  - `OTEL_EXPORTER_OTLP_ENDPOINT` -> `ExportConfig.endpoint`
+  - `OTEL_EXPORTER_OTLP_TIMEOUT` -> `ExportConfig.timeout`
 
 ## 0.28.0
 

opentelemetry-otlp/src/exporter/mod.rs

@@ -9,7 +9,6 @@ use crate::exporter::tonic::TonicExporterBuilder;
 use crate::Protocol;
 #[cfg(feature = "serialize")]
 use serde::{Deserialize, Serialize};
-use std::env;
 use std::fmt::{Display, Formatter};
 use std::str::FromStr;
 use std::time::Duration;
@@ -69,14 +68,19 @@ pub(crate) mod tonic;
 /// Configuration for the OTLP exporter.
 #[derive(Debug)]
 pub struct ExportConfig {
-    /// The address of the OTLP collector. If it's not provided via builder or environment variables.
+    /// The address of the OTLP collector.
     /// Default address will be used based on the protocol.
+    ///
+    /// Note: Programmatically setting this will override any value set via the environment variable.
     pub endpoint: Option<String>,
 
     /// The protocol to use when communicating with the collector.
     pub protocol: Protocol,
 
     /// The timeout to the collector.
+    /// The default value is 10 seconds.
+    ///
+    /// Note: Programmatically setting this will override any value set via the environment variable.
     pub timeout: Option<Duration>,
 }
 
@@ -224,18 +228,24 @@ impl HasExportConfig for HttpExporterBuilder {
 /// ```
 pub trait WithExportConfig {
     /// Set the address of the OTLP collector. If not set or set to empty string, the default address is used.
+    ///
+    /// Note: Programmatically setting this will override any value set via the environment variable.
     fn with_endpoint<T: Into<String>>(self, endpoint: T) -> Self;
     /// Set the protocol to use when communicating with the collector.
     ///
     /// Note that protocols that are not supported by exporters will be ignored. The exporter
     /// will use default protocol in this case.
     ///
     /// ## Note
-    /// All exporters in this crate only support one protocol, thus choosing the protocol is an no-op at the moment.
+    /// All exporters in this crate only support one protocol, thus choosing the protocol is a no-op at the moment.
     fn with_protocol(self, protocol: Protocol) -> Self;
     /// Set the timeout to the collector.
+    ///
+    /// Note: Programmatically setting this will override any value set via the environment variable.
     fn with_timeout(self, timeout: Duration) -> Self;
-    /// Set export config. This will override all previous configuration.
+    /// Set export config. This will override all previous configurations.
+    ///
+    /// Note: Programmatically setting this will override any value set via environment variables.
     fn with_export_config(self, export_config: ExportConfig) -> Self;
 }
 
@@ -263,17 +273,18 @@ impl<B: HasExportConfig> WithExportConfig for B {
     }
 }
 
+#[cfg(any(feature = "grpc-tonic", feature = "http-proto", feature = "http-json"))]
 fn resolve_timeout(signal_timeout_var: &str, provided_timeout: Option<&Duration>) -> Duration {
     // programmatic configuration overrides any value set via environment variables
     if let Some(timeout) = provided_timeout {
         *timeout
-    } else if let Some(timeout) = env::var(signal_timeout_var)
+    } else if let Some(timeout) = std::env::var(signal_timeout_var)
         .ok()
         .and_then(|s| s.parse().ok())
     {
         // per signal env var is not modified
         Duration::from_millis(timeout)
-    } else if let Some(timeout) = env::var(OTEL_EXPORTER_OTLP_TIMEOUT)
+    } else if let Some(timeout) = std::env::var(OTEL_EXPORTER_OTLP_TIMEOUT)
         .ok()
         .and_then(|s| s.parse().ok())
     {