Make the OTEL propagator configurable

crates/cli/src/telemetry.rs

@@ -14,8 +14,9 @@
 
 use std::time::Duration;
 
+use anyhow::bail;
 use futures::stream::{Stream, StreamExt};
-use mas_config::{MetricsConfig, TelemetryConfig, TracingConfig};
+use mas_config::{MetricsExporterConfig, Propagator, TelemetryConfig, TracingExporterConfig};
 use opentelemetry::{
     global,
     propagation::TextMapPropagator,
@@ -30,15 +31,15 @@ use opentelemetry_semantic_conventions as semcov;
 
 pub fn setup(config: &TelemetryConfig) -> anyhow::Result<Option<Tracer>> {
     global::set_error_handler(|e| tracing::error!("{}", e))?;
-    let propagator = propagator();
+    let propagator = propagator(&config.tracing.propagators)?;
 
     // The CORS filter needs to know what headers it should whitelist for
     // CORS-protected requests.
     mas_core::filters::cors::set_propagator(&propagator);
     global::set_text_map_propagator(propagator);
 
-    let tracer = tracer(&config.tracing)?;
-    meter(&config.metrics)?;
+    let tracer = tracer(&config.tracing.exporter)?;
+    meter(&config.metrics.exporter)?;
     Ok(tracer)
 }
 
@@ -46,15 +47,24 @@ pub fn shutdown() {
     global::shutdown_tracer_provider();
 }
 
-fn propagator() -> impl TextMapPropagator {
-    // TODO: make this configurable
-    let baggage_propagator = BaggagePropagator::new();
-    let trace_context_propagator = TraceContextPropagator::new();
+fn match_propagator(
+    propagator: Propagator,
+) -> anyhow::Result<Box<dyn TextMapPropagator + Send + Sync>> {
+    match propagator {
+        Propagator::TraceContext => Ok(Box::new(TraceContextPropagator::new())),
+        Propagator::Baggage => Ok(Box::new(BaggagePropagator::new())),
+        p => bail!(
+            "The service was compiled without support for the {:?} propagator, but config uses it.",
+            p
+        ),
+    }
+}
 
-    TextMapCompositePropagator::new(vec![
-        Box::new(baggage_propagator),
-        Box::new(trace_context_propagator),
-    ])
+fn propagator(propagators: &[Propagator]) -> anyhow::Result<impl TextMapPropagator> {
+    let propagators: Result<Vec<_>, _> =
+        propagators.iter().cloned().map(match_propagator).collect();
+
+    Ok(TextMapCompositePropagator::new(propagators?))
 }
 
 #[cfg(feature = "otlp")]
@@ -87,11 +97,11 @@ fn stdout_tracer() -> Tracer {
         .install_simple()
 }
 
-fn tracer(config: &TracingConfig) -> anyhow::Result<Option<Tracer>> {
+fn tracer(config: &TracingExporterConfig) -> anyhow::Result<Option<Tracer>> {
     let tracer = match config {
-        TracingConfig::None => return Ok(None),
-        TracingConfig::Stdout => stdout_tracer(),
-        TracingConfig::Otlp { endpoint } => otlp_tracer(endpoint)?,
+        TracingExporterConfig::None => return Ok(None),
+        TracingExporterConfig::Stdout => stdout_tracer(),
+        TracingExporterConfig::Otlp { endpoint } => otlp_tracer(endpoint)?,
     };
 
     Ok(Some(tracer))
@@ -131,11 +141,11 @@ fn stdout_meter() {
         .init();
 }
 
-fn meter(config: &MetricsConfig) -> anyhow::Result<()> {
+fn meter(config: &MetricsExporterConfig) -> anyhow::Result<()> {
     match config {
-        MetricsConfig::None => {}
-        MetricsConfig::Stdout => stdout_meter(),
-        MetricsConfig::Otlp { endpoint } => otlp_meter(endpoint)?,
+        MetricsExporterConfig::None => {}
+        MetricsExporterConfig::Stdout => stdout_meter(),
+        MetricsExporterConfig::Otlp { endpoint } => otlp_meter(endpoint)?,
     };
 
     Ok(())

crates/config/src/lib.rs

@@ -31,7 +31,10 @@ pub use self::{
     database::DatabaseConfig,
     http::HttpConfig,
     oauth2::{Algorithm, KeySet, OAuth2ClientConfig, OAuth2Config},
-    telemetry::{MetricsConfig, TelemetryConfig, TracingConfig},
+    telemetry::{
+        MetricsConfig, MetricsExporterConfig, Propagator, TelemetryConfig, TracingConfig,
+        TracingExporterConfig,
+    },
     templates::TemplatesConfig,
     util::ConfigurationSection,
 };

crates/config/src/telemetry.rs

@@ -19,10 +19,21 @@ use serde_with::skip_serializing_none;
 
 use super::ConfigurationSection;
 
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq, JsonSchema)]
+#[serde(rename_all = "lowercase")]
+#[non_exhaustive]
+pub enum Propagator {
+    TraceContext,
+    Baggage,
+    Jaeger,
+    B3,
+    B3Multi,
+}
+
 #[skip_serializing_none]
 #[derive(Clone, Debug, Serialize, Deserialize, JsonSchema)]
 #[serde(tag = "exporter", rename_all = "lowercase")]
-pub enum TracingConfig {
+pub enum TracingExporterConfig {
     None,
     Stdout,
     Otlp {
@@ -31,34 +42,49 @@ pub enum TracingConfig {
     },
 }
 
-impl Default for TracingConfig {
-    fn default() -> Self {
-        Self::None
-    }
-}
-
-#[skip_serializing_none]
-#[derive(Clone, Debug, Serialize, Deserialize, JsonSchema)]
-#[serde(tag = "exporter", rename_all = "lowercase")]
-pub enum MetricsConfig {
-    None,
-    Stdout,
-    Otlp {
-        #[serde(default)]
-        endpoint: Option<url::Url>,
-    },
-}
-
-impl Default for MetricsConfig {
+impl Default for TracingExporterConfig {
     fn default() -> Self {
         Self::None
     }
 }
 
+#[derive(Clone, Debug, Default, Serialize, Deserialize, JsonSchema)]
+pub struct TracingConfig {
+    #[serde(default, flatten)]
+    pub exporter: TracingExporterConfig,
+
+    pub propagators: Vec<Propagator>,
+}
+
+#[skip_serializing_none]
+#[derive(Clone, Debug, Serialize, Deserialize, JsonSchema)]
+#[serde(tag = "exporter", rename_all = "lowercase")]
+pub enum MetricsExporterConfig {
+    None,
+    Stdout,
+    Otlp {
+        #[serde(default)]
+        endpoint: Option<url::Url>,
+    },
+}
+
+impl Default for MetricsExporterConfig {
+    fn default() -> Self {
+        Self::None
+    }
+}
+
+#[derive(Clone, Debug, Default, Serialize, Deserialize, JsonSchema)]
+pub struct MetricsConfig {
+    #[serde(default, flatten)]
+    pub exporter: MetricsExporterConfig,
+}
+
 #[derive(Clone, Debug, Default, Serialize, Deserialize, JsonSchema)]
 pub struct TelemetryConfig {
     #[serde(default)]
     pub tracing: TracingConfig,
+
     #[serde(default)]
     pub metrics: MetricsConfig,
 }