Add support for external env (#509)

APMSP-1229

ddcommon/src/entity_id/mod.rs

@@ -1,14 +1,16 @@
 // Copyright 2021-Present Datadog, Inc. https://www.datadoghq.com/
 // SPDX-License-Identifier: Apache-2.0
 
-//! Extract the entity id and container id
+//! Extract the entity id, container id and external env
 //!
 //! The container id can be extracted from `/proc/self/group`
 //!
 //! The entity id is one of:
 //! - `cid:<container id>` if available
 //! - `in:<cgroup node inode>` if container id is not available (e.g. when using cgroupV2)
 //!
+//! The external env is an environment variable provided by the admission controller.
+//!
 //! # References
 //! - [DataDog/dd-trace-go](https://github.com/DataDog/dd-trace-go/blob/v1/internal/container.go)
 //! - [Qard/container-info](https://github.com/Qard/container-info/blob/master/index.js)
@@ -49,6 +51,11 @@
 //! 1:name=systemd:/ecs/8cd79a803caf4d2aa945152e934a5c00/8cd79a803caf4d2aa945152e934a5c00-1053176469
 //! ```
 
+use crate::config::parse_env;
+use lazy_static::lazy_static;
+
+const EXTERNAL_ENV_ENVIRONMENT_VARIABLE: &str = "DD_EXTERNAL_ENV";
+
 /// Unix specific module allowing the use of unix specific functions
 #[cfg(unix)]
 mod unix;
@@ -77,6 +84,15 @@ pub fn get_entity_id() -> Option<&'static str> {
     }
 }
 
+/// Returns the `DD_EXTERNAL_ENV` if available as an env variable
+pub fn get_external_env() -> Option<&'static str> {
+    lazy_static! {
+        static ref DD_EXTERNAL_ENV: Option<String> =
+            parse_env::str_not_empty(EXTERNAL_ENV_ENVIRONMENT_VARIABLE);
+    }
+    DD_EXTERNAL_ENV.as_deref()
+}
+
 /// Set the path to cgroup file to mock it during tests
 /// # Safety
 /// Must not be called in multi-threaded contexts

ddcommon/src/entity_id/unix/mod.rs

@@ -50,7 +50,7 @@ fn compute_entity_id(
 ) -> Option<String> {
     container_id::extract_container_id(cgroup_path)
         .ok()
-        .map(|container_id| format!("cid-{container_id}"))
+        .map(|container_id| format!("ci-{container_id}"))
         .or(
             cgroup_inode::get_cgroup_inode(base_controller, cgroup_path, cgroup_mount_path)
                 .map(|inode| format!("in-{inode}")),
@@ -119,8 +119,8 @@ mod tests {
 
     lazy_static! {
         static ref IN_REGEX: Regex = Regex::new(r"in-\d+").unwrap();
-        static ref CID_REGEX: Regex =
-            Regex::new(&format!(r"cid-{}", container_id::CONTAINER_REGEX.as_str())).unwrap();
+        static ref CI_REGEX: Regex =
+            Regex::new(&format!(r"ci-{}", container_id::CONTAINER_REGEX.as_str())).unwrap();
     }
 
     /// The following test can only be run in isolation because of caching behaviour introduced
@@ -161,7 +161,7 @@ mod tests {
 
     #[test]
     fn test_entity_id_for_container_id() {
-        test_entity_id("cgroup.docker", Some(&CID_REGEX))
+        test_entity_id("cgroup.docker", Some(&CI_REGEX))
     }
 
     #[test]

ddcommon/src/lib.rs

@@ -23,6 +23,7 @@ pub mod header {
     use hyper::{header::HeaderName, http::HeaderValue};
     pub const DATADOG_CONTAINER_ID: HeaderName = HeaderName::from_static("datadog-container-id");
     pub const DATADOG_ENTITY_ID: HeaderName = HeaderName::from_static("datadog-entity-id");
+    pub const DATADOG_EXTERNAL_ENV: HeaderName = HeaderName::from_static("datadog-external-env");
     pub const DATADOG_API_KEY: HeaderName = HeaderName::from_static("dd-api-key");
     pub const APPLICATION_JSON: HeaderValue = HeaderValue::from_static("application/json");
 }
@@ -146,6 +147,11 @@ impl Endpoint {
             builder = builder.header(header::DATADOG_ENTITY_ID, entity_id);
         }
 
+        // Add the External Env header if available
+        if let Some(external_env) = entity_id::get_external_env() {
+            builder = builder.header(header::DATADOG_EXTERNAL_ENV, external_env);
+        }
+
         Ok(builder)
     }
 }