feat: Add support for Resource attributes in ETW logs exporter (#410)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: cijothomas <5232798+cijothomas@users.noreply.github.com>
Co-authored-by: Cijo Thomas <cijo.thomas@gmail.com>
Co-authored-by: Lalit Kumar Bhasin <lalit_fin@yahoo.com>

Author: 3 people

opentelemetry-etw-logs/CHANGELOG.md

@@ -2,6 +2,15 @@
 
 ## vNext
 
+- Added a `with_resource_attributes` method to the processor builder, allowing
+  users to specify which resource attribute keys are exported with each log
+  record.
+  - By default, the Resource attributes `"service.name"` and
+    `"service.instance.id"` continue to be exported as `cloud.roleName` and
+    `cloud.roleInstance`.
+  - This feature enables exporting additional resource attributes beyond the
+    defaults.
+
 ## v0.10.0
 
 - Bump opentelemetry and opentelemetry_sdk versions to 0.31

opentelemetry-etw-logs/src/exporter/mod.rs

@@ -1,12 +1,14 @@
+use std::borrow::Cow;
 use std::cell::RefCell;
+use std::collections::HashSet;
 use std::fmt::Debug;
 use std::pin::Pin;
 use std::sync::Arc;
 
 use tracelogging_dynamic as tld;
 
 use opentelemetry::logs::Severity;
-use opentelemetry::Key;
+use opentelemetry::{logs::AnyValue, otel_debug, Key, Value};
 use opentelemetry_sdk::error::{OTelSdkError, OTelSdkResult};
 
 pub(crate) mod common;
@@ -26,12 +28,14 @@ thread_local! {
 struct Resource {
     pub cloud_role: Option<String>,
     pub cloud_role_instance: Option<String>,
+    pub attributes_from_resource: Vec<(Key, AnyValue)>,
 }
 
 pub(crate) struct ETWExporter {
     provider: Pin<Arc<tld::Provider>>,
     resource: Resource,
     options: Options,
+    resource_attribute_keys: HashSet<Cow<'static, str>>,
 }
 
 fn enabled_callback_noop(
@@ -65,9 +69,12 @@ impl ETWExporter {
             provider.as_ref().register();
         }
 
+        let resource_attribute_keys = options.resource_attribute_keys().clone();
+
         ETWExporter {
             provider,
             resource: Default::default(),
+            resource_attribute_keys,
             options,
         }
     }
@@ -110,7 +117,7 @@ impl ETWExporter {
 
             part_a::populate_part_a(event, &self.resource, log_record, field_tag);
 
-            let event_id = part_c::populate_part_c(event, log_record, field_tag);
+            let event_id = part_c::populate_part_c(event, log_record, &self.resource, field_tag);
 
             part_b::populate_part_b(event, log_record, otel_level, event_id);
 
@@ -150,12 +157,26 @@ impl opentelemetry_sdk::logs::LogExporter for ETWExporter {
     }
 
     fn set_resource(&mut self, resource: &opentelemetry_sdk::Resource) {
-        self.resource.cloud_role = resource
-            .get(&Key::from_static_str("service.name"))
-            .map(|v| v.to_string());
-        self.resource.cloud_role_instance = resource
-            .get(&Key::from_static_str("service.instance.id"))
-            .map(|v| v.to_string());
+        // Clear previous resource attributes
+        self.resource.attributes_from_resource.clear();
+
+        // Process resource attributes
+        for (key, value) in resource.iter() {
+            // Special handling for cloud role and instance
+            // as they are used in PartA of the Common Schema format.
+            if key.as_str() == "service.name" {
+                self.resource.cloud_role = Some(value.to_string());
+            } else if key.as_str() == "service.instance.id" {
+                self.resource.cloud_role_instance = Some(value.to_string());
+            } else if self.resource_attribute_keys.contains(key.as_str()) {
+                self.resource
+                    .attributes_from_resource
+                    .push((key.clone(), val_to_any_value(value)));
+            } else {
+                // Other attributes are ignored
+                otel_debug!(name: "UserEvents.ResourceAttributeIgnored", key = key.as_str(), message = "To include this attribute, add it via with_resource_attributes() method in the processor builder.");
+            }
+        }
     }
 
     fn shutdown(&self) -> OTelSdkResult {
@@ -169,6 +190,16 @@ impl opentelemetry_sdk::logs::LogExporter for ETWExporter {
     }
 }
 
+fn val_to_any_value(val: &Value) -> AnyValue {
+    match val {
+        Value::Bool(b) => AnyValue::Boolean(*b),
+        Value::I64(i) => AnyValue::Int(*i),
+        Value::F64(f) => AnyValue::Double(*f),
+        Value::String(s) => AnyValue::String(s.clone()),
+        _ => AnyValue::String("".into()),
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use opentelemetry_sdk::logs::LogExporter;
@@ -224,6 +255,60 @@ mod tests {
         assert!(result.is_ok());
     }
 
+    #[test]
+    fn test_event_resources_with_custom_attributes() {
+        use opentelemetry::logs::LogRecord;
+        use opentelemetry::KeyValue;
+
+        let mut log_record = common::test_utils::new_sdk_log_record();
+        log_record.set_event_name("event-name");
+
+        // Create exporter with custom resource attributes
+        let options = Options::new("test_provider")
+            .with_resource_attributes(vec!["custom_attribute1", "custom_attribute2"]);
+
+        let mut exporter = ETWExporter::new(options);
+
+        exporter.set_resource(
+            &opentelemetry_sdk::Resource::builder()
+                .with_attributes([
+                    KeyValue::new("service.name", "test-service"),
+                    KeyValue::new("service.instance.id", "test-instance"),
+                    KeyValue::new("custom_attribute1", "value1"),
+                    KeyValue::new("custom_attribute2", "value2"),
+                    KeyValue::new("custom_attribute3", "value3"), // This should be ignored
+                ])
+                .build(),
+        );
+
+        // Verify that only the configured attributes are stored
+        assert_eq!(
+            exporter.resource.cloud_role,
+            Some("test-service".to_string())
+        );
+        assert_eq!(
+            exporter.resource.cloud_role_instance,
+            Some("test-instance".to_string())
+        );
+        assert_eq!(exporter.resource.attributes_from_resource.len(), 2);
+
+        // Check that the correct attributes are stored
+        let attrs: std::collections::HashMap<String, String> = exporter
+            .resource
+            .attributes_from_resource
+            .iter()
+            .map(|(k, v)| (k.as_str().to_string(), format!("{:?}", v)))
+            .collect();
+        assert!(attrs.contains_key("custom_attribute1"));
+        assert!(attrs.contains_key("custom_attribute2"));
+        assert!(!attrs.contains_key("custom_attribute3"));
+
+        let instrumentation = common::test_utils::new_instrumentation_scope();
+        let result = exporter.export_log_data(&log_record, &instrumentation);
+
+        assert!(result.is_ok());
+    }
+
     #[test]
     fn test_debug() {
         let exporter = common::test_utils::new_etw_exporter();

opentelemetry-etw-logs/src/exporter/options.rs

@@ -1,5 +1,6 @@
 use opentelemetry_sdk::logs::SdkLogRecord;
 use std::borrow::Cow;
+use std::collections::HashSet;
 use std::error::Error;
 
 type BoxedEventNameCallback = Box<dyn EventNameCallback>;
@@ -8,13 +9,15 @@ type BoxedEventNameCallback = Box<dyn EventNameCallback>;
 pub(crate) struct Options {
     provider_name: Cow<'static, str>,
     event_name_callback: Option<BoxedEventNameCallback>,
+    resource_attribute_keys: HashSet<Cow<'static, str>>,
 }
 
 impl Options {
     pub(crate) fn new(provider_name: impl Into<Cow<'static, str>>) -> Options {
         Options {
             provider_name: provider_name.into(),
             event_name_callback: None,
+            resource_attribute_keys: HashSet::new(),
         }
     }
 
@@ -23,6 +26,21 @@ impl Options {
         &self.provider_name
     }
 
+    /// Returns the resource attribute keys that will be exported with each log record.
+    pub(crate) fn resource_attribute_keys(&self) -> &HashSet<Cow<'static, str>> {
+        &self.resource_attribute_keys
+    }
+
+    /// Sets the resource attributes for the exporter.
+    pub(crate) fn with_resource_attributes<I, S>(mut self, attributes: I) -> Self
+    where
+        I: IntoIterator<Item = S>,
+        S: Into<Cow<'static, str>>,
+    {
+        self.resource_attribute_keys = attributes.into_iter().map(|s| s.into()).collect();
+        self
+    }
+
     /// Returns the default event name that will be used for the ETW events.
     pub(crate) fn default_event_name(&self) -> &str {
         "Log"

opentelemetry-etw-logs/src/exporter/part_c.rs

@@ -6,6 +6,7 @@ pub(crate) const EVENT_ID: &str = "event_id";
 pub(crate) fn populate_part_c(
     event: &mut tld::EventBuilder,
     log_record: &opentelemetry_sdk::logs::SdkLogRecord,
+    resource: &super::Resource,
     field_tag: u32,
 ) -> Option<i64> {
     //populate CS PartC
@@ -25,9 +26,17 @@ pub(crate) fn populate_part_c(
         }
     }
 
+    // Count resource attributes
+    cs_c_count += resource.attributes_from_resource.len();
+
     // If there are additional PartC attributes, add them to the event
     if cs_c_count > 0 {
-        event.add_struct("PartC", cs_c_count, field_tag);
+        event.add_struct("PartC", cs_c_count.try_into().unwrap_or(u8::MAX), field_tag);
+
+        // Add resource attributes first
+        for (key, value) in &resource.attributes_from_resource {
+            super::common::add_attribute_to_event(event, key, value);
+        }
 
         // TODO: This 2nd iteration is not optimal, and can be optimized
         for (key, value) in log_record.attributes_iter() {

opentelemetry-etw-logs/src/lib.rs

@@ -1,5 +1,64 @@
 //! The ETW exporter will enable applications to use OpenTelemetry API
 //! to capture the telemetry events, and write them to the ETW subsystem.
+//!
+//! ## Resource Attribute Handling
+//!
+//! **Important**: By default, resource attributes are NOT exported with log records.
+//! The ETW exporter only automatically exports these specific resource attributes:
+//!
+//! - **`service.name`** → Exported as `cloud.roleName` in PartA of Common Schema
+//! - **`service.instance.id`** → Exported as `cloud.roleInstance` in PartA of Common Schema
+//!
+//! All other resource attributes are ignored unless explicitly specified.
+//!
+//! ### Opting in to Additional Resource Attributes
+//!
+//! To export additional resource attributes, use the `with_resource_attributes()` method:
+//!
+//! ```rust
+//! use opentelemetry_sdk::logs::SdkLoggerProvider;
+//! use opentelemetry_sdk::Resource;
+//! use opentelemetry_etw_logs::Processor;
+//! use opentelemetry::KeyValue;
+//!
+//! let etw_processor = Processor::builder("myprovider")
+//!     // Only export specific resource attributes
+//!     .with_resource_attributes(["custom_attribute1", "custom_attribute2"])
+//!     .build()
+//!     .unwrap();
+//!
+//! let provider = SdkLoggerProvider::builder()
+//!     .with_resource(
+//!         Resource::builder_empty()
+//!             .with_service_name("example")
+//!             .with_attribute(KeyValue::new("custom_attribute1", "value1"))
+//!             .with_attribute(KeyValue::new("custom_attribute2", "value2"))
+//!             .with_attribute(KeyValue::new("custom_attribute3", "value3"))  // This won't be exported
+//!             .build(),
+//!     )
+//!     .with_log_processor(etw_processor)
+//!     .build();
+//! ```
+//!
+//! ### Performance Considerations for ETW
+//!
+//! **Warning**: Each specified resource attribute will be serialized and sent
+//! with EVERY log record. This is different from OTLP exporters where resource
+//! attributes are serialized once per batch. Consider the performance impact
+//! when selecting which attributes to export.
+//!
+//! **Recommendation**: Be selective about which resource attributes to export.
+//! Since ETW writes to a local kernel buffer and requires a local
+//! listener/agent, the agent can often deduce many resource attributes without
+//! requiring them to be sent with each log:
+//!
+//! - **Infrastructure attributes** (datacenter, region, availability zone) can
+//!   be determined by the local agent.
+//! - **Host attributes** (hostname, IP address, OS version) are available locally.
+//! - **Deployment attributes** (environment, cluster) may be known to the agent.
+//!
+//! Focus on attributes that are truly specific to your application instance
+//! and cannot be easily determined by the local agent.
 
 #![warn(missing_debug_implementations, missing_docs)]