feat: Add host.id resource detector (#57)

Add the Host Resource detector retrieving the "host.id" as defined in: https://opentelemetry.io/docs/specs/semconv/resource/host/

Defined in #56

opentelemetry-resource-detectors/CHANGELOG.md

@@ -1,5 +1,11 @@
 # Changelog
 
+## vNext
+
+### Added
+
+- Added `HostResourceDetector` which populates "host.id" attribute. Currently only Linux is supported.
+
 ## v0.1.0
 
 ### Added

opentelemetry-resource-detectors/README.md

@@ -12,7 +12,8 @@ Community supported Resource detectors implementations for applications instrume
 
 ## Features
 
-| Detector       | Implemented Resources                               | Semantic Conventions       |
-| -------------- | --------------------------------------------------- | -------------------------- |
-| ProcessResourceDetector | PROCESS_COMMAND_ARGS, PROCESS_PID | https://github.com/open-telemetry/opentelemetry-specification/blob/v1.6.x/specification/resource/semantic_conventions/process.md |
-| OsResourceDetector  | OS_TYPE | https://github.com/open-telemetry/opentelemetry-specification/blob/v1.6.x/specification/resource/semantic_conventions/os.md |
+| Detector                | Implemented Resources                               | OS Supported | Semantic Conventions                                                                      |
+|-------------------------| --------------------------------------------------- |--------------|-------------------------------------------------------------------------------------------|
+| ProcessResourceDetector | PROCESS_COMMAND_ARGS, PROCESS_PID | all          | https://github.com/open-telemetry/semantic-conventions/blob/main/docs/resource/process.md |
+| OsResourceDetector      | OS_TYPE | all          | https://github.com/open-telemetry/semantic-conventions/blob/main/docs/resource/os.md      |
+| HostResourceDetector    | HOST_ID | linux        | https://github.com/open-telemetry/semantic-conventions/blob/main/docs/resource/host.md    |

opentelemetry-resource-detectors/src/host.rs

@@ -0,0 +1,73 @@
+//! HOST resource detector
+//!
+//! Detect the unique host ID.
+use opentelemetry::KeyValue;
+use opentelemetry_sdk::resource::ResourceDetector;
+use opentelemetry_sdk::Resource;
+use std::fs::read_to_string;
+use std::path::Path;
+use std::time::Duration;
+
+/// Detect the unique host ID.
+///
+/// This detector looks up the host id using the sources defined
+/// in the OpenTelemetry semantic conventions [`host.id from non-containerized systems`].
+///
+/// [`host.id from non-containerized systems`]: https://opentelemetry.io/docs/specs/semconv/resource/host/#collecting-hostid-from-non-containerized-systems
+pub struct HostResourceDetector {
+    host_id_detect: fn() -> Option<String>,
+}
+
+impl ResourceDetector for HostResourceDetector {
+    fn detect(&self, _timeout: Duration) -> Resource {
+        (self.host_id_detect)()
+            .map(|host_id| {
+                Resource::new(vec![KeyValue::new(
+                    opentelemetry_semantic_conventions::resource::HOST_ID,
+                    host_id,
+                )])
+            })
+            .unwrap_or(Resource::new(vec![]))
+    }
+}
+
+#[cfg(target_os = "linux")]
+fn host_id_detect() -> Option<String> {
+    let machine_id_path = Path::new("/etc/machine-id");
+    let dbus_machine_id_path = Path::new("/var/lib/dbus/machine-id");
+    read_to_string(machine_id_path)
+        .or_else(|_| read_to_string(dbus_machine_id_path))
+        .ok()
+}
+
+// TODO: Implement non-linux platforms
+#[cfg(not(target_os = "linux"))]
+fn host_id_detect() -> Option<String> {
+    None
+}
+
+impl Default for HostResourceDetector {
+    fn default() -> Self {
+        Self { host_id_detect }
+    }
+}
+
+#[cfg(target_os = "linux")]
+#[cfg(test)]
+mod tests {
+    use super::HostResourceDetector;
+    use opentelemetry::Key;
+    use opentelemetry_sdk::resource::ResourceDetector;
+    use std::time::Duration;
+
+    #[test]
+    fn test_host_resource_detector() {
+        let resource = HostResourceDetector::default().detect(Duration::from_secs(0));
+        assert_eq!(resource.len(), 1);
+        assert!(resource
+            .get(Key::from_static_str(
+                opentelemetry_semantic_conventions::resource::HOST_ID
+            ))
+            .is_some())
+    }
+}

opentelemetry-resource-detectors/src/lib.rs

@@ -5,8 +5,11 @@
 //!
 //! - [`OsResourceDetector`] - detect OS from runtime.
 //! - [`ProcessResourceDetector`] - detect process information.
+//! - [`HostResourceDetector`] - detect unique host ID.
+mod host;
 mod os;
 mod process;
 
+pub use host::HostResourceDetector;
 pub use os::OsResourceDetector;
 pub use process::ProcessResourceDetector;