feat: w3c field

.github/workflows/run-integration-test.yml

@@ -54,13 +54,16 @@ jobs:
             sam deploy --stack-name "${stackName}" --parameter-overrides "ParameterKey=SecretToken,ParameterValue=${{ secrets.SECRET_TOKEN }}" "ParameterKey=LambdaRole,ParameterValue=${{ secrets.AWS_LAMBDA_ROLE }}" --no-confirm-changeset  --no-progressbar  > disable_output
             TEST_ENDPOINT=$(sam list stack-outputs --stack-name "${stackName}" --output json | jq -r '.[] | select(.OutputKey=="HelloApiEndpoint") | .OutputValue')
             TENANT_ID_TEST_FUNCTION=$(sam list stack-outputs --stack-name "${stackName}" --output json | jq -r '.[] | select(.OutputKey=="TenantIdTestFunction") | .OutputValue')
+            W3C_TEST_FUNCTION=$(sam list stack-outputs --stack-name "${stackName}" --output json | jq -r '.[] | select(.OutputKey=="W3CTestFunction") | .OutputValue')
             echo "TEST_ENDPOINT=$TEST_ENDPOINT" >> "$GITHUB_OUTPUT"
             echo "TENANT_ID_TEST_FUNCTION=$TENANT_ID_TEST_FUNCTION" >> "$GITHUB_OUTPUT"
+            echo "W3C_TEST_FUNCTION=$W3C_TEST_FUNCTION" >> "$GITHUB_OUTPUT"
         - name: run test
           env:
             SECRET_TOKEN: ${{ secrets.SECRET_TOKEN }}
             TEST_ENDPOINT: ${{ steps.deploy_stack.outputs.TEST_ENDPOINT }}
             TENANT_ID_TEST_FUNCTION: ${{ steps.deploy_stack.outputs.TENANT_ID_TEST_FUNCTION }}
+            W3C_TEST_FUNCTION: ${{ steps.deploy_stack.outputs.W3C_TEST_FUNCTION }}
           run: cd lambda-integration-tests && cargo test
         - name: cleanup
           if: always() && steps.deploy_stack.outputs.STACK_NAME

lambda-integration-tests/Cargo.toml

@@ -21,6 +21,7 @@ tracing = "0.1"
 
 [dev-dependencies]
 reqwest = { version = "0.13.1", features = ["blocking"] }
+base64 = "0.22.1"
 
 [features]
 catch-all-fields = ["aws_lambda_events/catch-all-fields"]
@@ -36,3 +37,7 @@ path = "src/authorizer.rs"
 [[bin]]
 name = "tenant-id-test"
 path = "src/tenant_id_test.rs"
+
+[[bin]]
+name = "w3c-test"
+path = "src/w3c_test.rs"

lambda-integration-tests/src/w3c_test.rs

@@ -0,0 +1,34 @@
+use lambda_runtime::{service_fn, Error, LambdaEvent};
+use serde_json::{json, Value};
+
+async fn function_handler(event: LambdaEvent<Value>) -> Result<Value, Error> {
+    let (_event, context) = event.into_parts();
+
+    let w3c_fields = context.w3c();
+    tracing::info!("w3c fields observed on context: {:?}", w3c_fields);
+
+    let client_context_has_custom = context
+        .client_context
+        .as_ref()
+        .map(|cc| !cc.custom.is_empty())
+        .unwrap_or(false);
+
+    let response = json!({
+        "statusCode": 200,
+        "body": json!({
+            "message": "W3C test successful",
+            "request_id": context.request_id,
+            "w3c": w3c_fields,
+            "has_client_context": context.client_context.is_some(),
+            "client_context_has_custom": client_context_has_custom,
+        }).to_string()
+    });
+
+    Ok(response)
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Error> {
+    lambda_runtime::tracing::init_default_subscriber();
+    lambda_runtime::run(service_fn(function_handler)).await
+}

lambda-integration-tests/template.yaml

@@ -53,6 +53,18 @@ Resources:
       Runtime: provided.al2023
       Role: !Ref LambdaRole
 
+  W3CTestFunction:
+    Type: AWS::Serverless::Function
+    Metadata:
+      BuildMethod: rust-cargolambda
+      BuildProperties:
+        Binary: w3c-test
+    Properties:
+      CodeUri: ./
+      Handler: bootstrap
+      Runtime: provided.al2023
+      Role: !Ref LambdaRole
+
   AuthorizerFunction:
     Type: AWS::Serverless::Function
     Metadata:
@@ -74,4 +86,7 @@ Outputs:
     Value: !Sub "https://${API}.execute-api.${AWS::Region}.amazonaws.com/integ-test/hello/"
   TenantIdTestFunction:
     Description: "Tenant ID test function name"
-    Value: !Ref TenantIdTestFunction
+    Value: !Ref TenantIdTestFunction
+  W3CTestFunction:
+    Description: "W3C trace-context test function name"
+    Value: !Ref W3CTestFunction

lambda-integration-tests/tests/w3c_prod_test.rs

@@ -0,0 +1,107 @@
+use base64::prelude::*;
+use serde_json::json;
+
+fn function_name() -> String {
+    std::env::var("W3C_TEST_FUNCTION").expect("W3C_TEST_FUNCTION environment variable not set")
+}
+
+/// Invoke the deployed Lambda function and return the parsed body JSON.
+fn invoke(payload: &serde_json::Value, client_context_json: Option<&serde_json::Value>) -> serde_json::Value {
+    let response_path = format!(
+        "/tmp/w3c_response_{}.json",
+        std::time::SystemTime::now()
+            .duration_since(std::time::UNIX_EPOCH)
+            .unwrap()
+            .as_nanos()
+    );
+
+    let mut args: Vec<String> = vec![
+        "lambda".into(),
+        "invoke".into(),
+        "--function-name".into(),
+        function_name(),
+        "--payload".into(),
+        payload.to_string(),
+        "--cli-binary-format".into(),
+        "raw-in-base64-out".into(),
+    ];
+
+    if let Some(cc) = client_context_json {
+        let encoded = BASE64_STANDARD.encode(cc.to_string());
+        args.push("--client-context".into());
+        args.push(encoded);
+    }
+
+    args.push(response_path.clone());
+
+    let output = std::process::Command::new("aws")
+        .args(&args)
+        .output()
+        .expect("Failed to invoke Lambda function");
+
+    assert!(
+        output.status.success(),
+        "Lambda invocation failed: {}",
+        String::from_utf8_lossy(&output.stderr)
+    );
+
+    let response = std::fs::read_to_string(&response_path).expect("Failed to read response file");
+    let response_json: serde_json::Value = serde_json::from_str(&response).expect("Failed to parse response JSON");
+
+    assert_eq!(
+        response_json["statusCode"],
+        200,
+        "handler returned non-200: {}",
+        serde_json::to_string_pretty(&response_json).unwrap()
+    );
+
+    let body: serde_json::Value =
+        serde_json::from_str(response_json["body"].as_str().expect("Body should be a string"))
+            .expect("Failed to parse body JSON");
+
+    let _ = std::fs::remove_file(&response_path);
+    body
+}
+
+#[test]
+fn test_w3c_propagation_in_production() {
+    // 1. No client context — `context.w3c()` must be empty.
+    let body = invoke(&json!({ "test": "w3c_no_client_context" }), None);
+    assert_eq!(body["message"], "W3C test successful");
+    assert_eq!(body["has_client_context"], false);
+    assert_eq!(
+        body["w3c"],
+        json!({}),
+        "w3c should be empty when no clientContext header is present, got: {}",
+        body["w3c"]
+    );
+
+    // 2. Client context carrying `w3c` + a sibling `custom` field — `w3c()`
+    //    must surface all three allowlisted fields, and the sibling `custom`
+    //    must still be reachable on `context.client_context` (the `w3c` key
+    //    was stripped during Context construction, not the whole object).
+    let client_context = json!({
+        "custom": { "source": "integ-test" },
+        "w3c": {
+            "traceparent": "00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01",
+            "tracestate": "rojo=00f067aa0ba902b7",
+            "baggage": "userId=alice"
+        }
+    });
+
+    let body = invoke(&json!({ "test": "w3c_with_client_context" }), Some(&client_context));
+    assert_eq!(body["message"], "W3C test successful");
+    assert_eq!(body["has_client_context"], true);
+    assert_eq!(
+        body["client_context_has_custom"], true,
+        "sibling clientContext fields must still be reachable after w3c is stripped"
+    );
+    assert_eq!(
+        body["w3c"]["traceparent"],
+        "00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-01"
+    );
+    assert_eq!(body["w3c"]["tracestate"], "rojo=00f067aa0ba902b7");
+    assert_eq!(body["w3c"]["baggage"], "userId=alice");
+
+    println!("✅ W3C trace-context propagation test passed");
+}

lambda-runtime/src/constants.rs

@@ -7,3 +7,4 @@ pub(crate) const LAMBDA_RUNTIME_CLIENT_CONTEXT: &str = "lambda-runtime-client-co
 pub(crate) const LAMBDA_RUNTIME_COGNITO_IDENTITY: &str = "lambda-runtime-cognito-identity";
 pub(crate) const LAMBDA_RUNTIME_TENANT_ID: &str = "lambda-runtime-aws-tenant-id";
 pub(crate) const LAMBDA_RUNTIME_INVOCATION_ID: &str = "lambda-runtime-invocation-id";
+pub(crate) const W3C_ALLOWED_FIELDS: &[&str] = &["traceparent", "tracestate", "baggage"];