impl(gax-internal): define InstrumentationClientInfo for tracing (#3347)

Author: westarle

src/gax-internal/src/http.rs

@@ -39,6 +39,7 @@ pub struct ReqwestClient {
     retry_throttler: SharedRetryThrottler,
     polling_error_policy: Arc<dyn PollingErrorPolicy>,
     polling_backoff_policy: Arc<dyn PollingBackoffPolicy>,
+    instrumentation: Option<crate::options::InstrumentationClientInfo>,
 }
 
 impl ReqwestClient {
@@ -79,9 +80,18 @@ impl ReqwestClient {
             polling_backoff_policy: config
                 .polling_backoff_policy
                 .unwrap_or_else(|| Arc::new(ExponentialBackoff::default())),
+            instrumentation: None,
         })
     }
 
+    pub fn with_instrumentation(
+        mut self,
+        instrumentation: Option<crate::options::InstrumentationClientInfo>,
+    ) -> Self {
+        self.instrumentation = instrumentation;
+        self
+    }
+
     pub fn builder(&self, method: Method, path: String) -> reqwest::RequestBuilder {
         self.inner
             .request(method, format!("{}{path}", &self.endpoint))
@@ -280,6 +290,9 @@ mod tests {
     use http::{HeaderMap, HeaderValue, Method};
     use test_case::test_case;
     type TestResult = std::result::Result<(), Box<dyn std::error::Error>>;
+    use super::*;
+    use crate::options::ClientConfig;
+    use crate::options::InstrumentationClientInfo;
 
     #[tokio::test]
     async fn client_http_error_bytes() -> TestResult {
@@ -405,4 +418,40 @@ mod tests {
     fn default_idempotency(input: Method, expected: bool) {
         assert!(super::default_idempotency(&input) == expected);
     }
+
+    static TEST_INSTRUMENTATION_INFO: InstrumentationClientInfo = InstrumentationClientInfo {
+        service_name: "test-service",
+        client_version: "1.2.3",
+        client_artifact: "test-artifact",
+        default_host: "test.googleapis.com",
+    };
+
+    #[tokio::test]
+    async fn reqwest_client_new() {
+        let config = ClientConfig::default();
+        let client = ReqwestClient::new(config, "https://test.googleapis.com")
+            .await
+            .unwrap();
+        assert!(client.instrumentation.is_none());
+    }
+
+    #[tokio::test]
+    async fn reqwest_client_with_instrumentation() {
+        let config = ClientConfig::default();
+        let client = ReqwestClient::new(config, "https://test.googleapis.com")
+            .await
+            .unwrap();
+        assert!(client.instrumentation.is_none());
+
+        let client = client.with_instrumentation(Some(TEST_INSTRUMENTATION_INFO));
+        assert!(client.instrumentation.is_some());
+        let info = client.instrumentation.unwrap();
+        assert_eq!(info.service_name, "test-service");
+        assert_eq!(info.client_version, "1.2.3");
+        assert_eq!(info.client_artifact, "test-artifact");
+        assert_eq!(info.default_host, "test.googleapis.com");
+
+        let client = client.with_instrumentation(None);
+        assert!(client.instrumentation.is_none());
+    }
 }

src/gax-internal/src/options.rs

@@ -19,6 +19,19 @@ pub type ClientConfig = gax::client_builder::internal::ClientConfig<Credentials>
 
 pub(crate) const LOGGING_VAR: &str = "GOOGLE_CLOUD_RUST_LOGGING";
 
+/// Information about the client library used for instrumentation.
+#[derive(Copy, Clone, Debug)]
+pub struct InstrumentationClientInfo {
+    /// The short service name, e.g., "appengine", "run", "firestore".
+    pub service_name: &'static str,
+    /// The version of the client library.
+    pub client_version: &'static str,
+    /// The name of the client library artifact (e.g., crate name).
+    pub client_artifact: &'static str,
+    /// The default hostname of the service.
+    pub default_host: &'static str,
+}
+
 // Returns true if the environment or client configuration enables tracing.
 pub fn tracing_enabled(config: &ClientConfig) -> bool {
     if config.tracing {