feat: opentelemetry-tracing (#3)

Co-authored-by: Sharang Parnerkar <parnerkarsharang@gmail.com>
Reviewed-on: #3

compliance-core/Cargo.toml

@@ -9,6 +9,15 @@ workspace = true
 [features]
 default = ["mongodb"]
 mongodb = ["dep:mongodb"]
+telemetry = [
+    "dep:opentelemetry",
+    "dep:opentelemetry_sdk",
+    "dep:opentelemetry-otlp",
+    "dep:opentelemetry-appender-tracing",
+    "dep:tracing-opentelemetry",
+    "dep:tracing-subscriber",
+    "dep:tracing",
+]
 
 [dependencies]
 serde = { workspace = true }
@@ -21,3 +30,10 @@ uuid = { workspace = true }
 secrecy = { workspace = true }
 bson = { version = "2", features = ["chrono-0_4"] }
 mongodb = { workspace = true, optional = true }
+opentelemetry = { version = "0.29", optional = true }
+opentelemetry_sdk = { version = "0.29", features = ["rt-tokio"], optional = true }
+opentelemetry-otlp = { version = "0.29", features = ["grpc-tonic"], optional = true }
+opentelemetry-appender-tracing = { version = "0.29", optional = true }
+tracing-opentelemetry = { version = "0.30", optional = true }
+tracing-subscriber = { workspace = true, optional = true }
+tracing = { workspace = true, optional = true }

compliance-core/src/lib.rs

@@ -1,6 +1,8 @@
 pub mod config;
 pub mod error;
 pub mod models;
+#[cfg(feature = "telemetry")]
+pub mod telemetry;
 pub mod traits;
 
 pub use config::{AgentConfig, DashboardConfig};

compliance-core/src/telemetry.rs

@@ -0,0 +1,150 @@
+//! OpenTelemetry initialization for traces and logs.
+//!
+//! Exports traces and logs via OTLP (gRPC) when `OTEL_EXPORTER_OTLP_ENDPOINT`
+//! is set. Always includes a `tracing_subscriber::fmt` layer for console output.
+//!
+//! Compatible with SigNoz, Grafana Tempo/Loki, Jaeger, and any OTLP-compatible
+//! collector.
+//!
+//! # Environment Variables
+//!
+//! | Variable | Description | Default |
+//! |---|---|---|
+//! | `OTEL_EXPORTER_OTLP_ENDPOINT` | OTLP collector endpoint (e.g. `http://localhost:4317`) | *(disabled)* |
+//! | `OTEL_SERVICE_NAME` | Service name for resource | `service_name` param |
+//! | `RUST_LOG` / standard `EnvFilter` | Log level filter | `info` |
+
+use opentelemetry::global;
+use opentelemetry::trace::TracerProvider as _;
+use opentelemetry::KeyValue;
+use opentelemetry_appender_tracing::layer::OpenTelemetryTracingBridge;
+use opentelemetry_otlp::{LogExporter, SpanExporter, WithExportConfig};
+use opentelemetry_sdk::{logs::SdkLoggerProvider, trace::SdkTracerProvider, Resource};
+use tracing_opentelemetry::OpenTelemetryLayer;
+use tracing_subscriber::{layer::SubscriberExt, util::SubscriberInitExt, EnvFilter, Layer as _};
+
+/// Guard that shuts down OTel providers on drop.
+///
+/// Must be held for the lifetime of the application. When dropped,
+/// flushes and shuts down the tracer and logger providers.
+pub struct TelemetryGuard {
+    tracer_provider: Option<SdkTracerProvider>,
+    logger_provider: Option<SdkLoggerProvider>,
+}
+
+impl Drop for TelemetryGuard {
+    fn drop(&mut self) {
+        if let Some(tp) = self.tracer_provider.take() {
+            if let Err(e) = tp.shutdown() {
+                eprintln!("Failed to shutdown tracer provider: {e}");
+            }
+        }
+        if let Some(lp) = self.logger_provider.take() {
+            if let Err(e) = lp.shutdown() {
+                eprintln!("Failed to shutdown logger provider: {e}");
+            }
+        }
+    }
+}
+
+fn build_resource(service_name: &str) -> Resource {
+    let name = std::env::var("OTEL_SERVICE_NAME").unwrap_or_else(|_| service_name.to_string());
+    Resource::builder()
+        .with_service_name(name)
+        .with_attributes([KeyValue::new("service.version", env!("CARGO_PKG_VERSION"))])
+        .build()
+}
+
+/// Initialize telemetry (tracing + logging).
+///
+/// If `OTEL_EXPORTER_OTLP_ENDPOINT` is set, traces and logs are exported
+/// via OTLP/gRPC. Console fmt output is always enabled.
+///
+/// Returns a [`TelemetryGuard`] that must be held alive for the application
+/// lifetime. Dropping it triggers a graceful shutdown of OTel providers.
+///
+/// # Panics
+///
+/// Panics if the tracing subscriber cannot be initialized (e.g. called twice).
+pub fn init_telemetry(service_name: &str) -> TelemetryGuard {
+    let otel_endpoint = std::env::var("OTEL_EXPORTER_OTLP_ENDPOINT").ok();
+
+    let env_filter = EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new("info"));
+    let fmt_layer = tracing_subscriber::fmt::layer();
+
+    match otel_endpoint {
+        Some(ref endpoint) => {
+            let resource = build_resource(service_name);
+
+            // Traces
+            #[allow(clippy::expect_used)]
+            let span_exporter = SpanExporter::builder()
+                .with_tonic()
+                .with_endpoint(endpoint)
+                .build()
+                .expect("failed to create OTLP span exporter");
+
+            let tracer_provider = SdkTracerProvider::builder()
+                .with_batch_exporter(span_exporter)
+                .with_resource(resource.clone())
+                .build();
+
+            global::set_tracer_provider(tracer_provider.clone());
+            let tracer = tracer_provider.tracer(service_name.to_string());
+            let otel_trace_layer = OpenTelemetryLayer::new(tracer);
+
+            // Logs
+            #[allow(clippy::expect_used)]
+            let log_exporter = LogExporter::builder()
+                .with_tonic()
+                .with_endpoint(endpoint)
+                .build()
+                .expect("failed to create OTLP log exporter");
+
+            let logger_provider = SdkLoggerProvider::builder()
+                .with_batch_exporter(log_exporter)
+                .with_resource(resource)
+                .build();
+
+            let otel_log_layer = OpenTelemetryTracingBridge::new(&logger_provider);
+
+            // Filter to prevent telemetry-induced-telemetry loops
+            let otel_filter = EnvFilter::new("info")
+                .add_directive("hyper=off".parse().unwrap_or_default())
+                .add_directive("tonic=off".parse().unwrap_or_default())
+                .add_directive("h2=off".parse().unwrap_or_default())
+                .add_directive("reqwest=off".parse().unwrap_or_default());
+
+            tracing_subscriber::registry()
+                .with(env_filter)
+                .with(fmt_layer)
+                .with(otel_trace_layer)
+                .with(otel_log_layer.with_filter(otel_filter))
+                .init();
+
+            tracing::info!(
+                endpoint = endpoint.as_str(),
+                service = service_name,
+                "OpenTelemetry OTLP export enabled"
+            );
+
+            TelemetryGuard {
+                tracer_provider: Some(tracer_provider),
+                logger_provider: Some(logger_provider),
+            }
+        }
+        None => {
+            tracing_subscriber::registry()
+                .with(env_filter)
+                .with(fmt_layer)
+                .init();
+
+            tracing::info!("OpenTelemetry disabled (set OTEL_EXPORTER_OTLP_ENDPOINT to enable)");
+
+            TelemetryGuard {
+                tracer_provider: None,
+                logger_provider: None,
+            }
+        }
+    }
+}