add observability infrastructure for cli subcmds

src/observability.rs

@@ -18,7 +18,7 @@ use opentelemetry_sdk::{
 };
 use strum::{AsRefStr, IntoStaticStr};
 use tokio::time::Instant;
-use tracing::Span;
+use tracing::{subscriber::SetGlobalDefaultError, Span};
 use tracing_flame::{FlameLayer, FlushGuard};
 use tracing_opentelemetry::OtelData;
 use tracing_subscriber::{
@@ -469,3 +469,27 @@ pub(crate) async fn traceresponse_layer(req: Request, next: Next) -> Response {
 
     resp
 }
+
+/// Set up observability for CLI-oriented subcommands.
+///
+/// Tracing spans and events will be sent to `stderr`.
+pub(crate) fn init_for_cli(
+    log_format: LogFormat,
+    env_filter: EnvFilter,
+) -> Result<(), SetGlobalDefaultError> {
+    let log_layer =
+        tracing_subscriber::fmt::Layer::new().with_writer(std::io::stderr);
+
+    let log_layer = match log_format {
+        LogFormat::Pretty => log_layer.pretty().boxed(),
+        LogFormat::Full => log_layer.boxed(),
+        LogFormat::Compact => log_layer.compact().boxed(),
+        LogFormat::Json => log_layer.json().boxed(),
+    };
+
+    let log_layer = log_layer.with_filter(env_filter);
+
+    let subscriber = Registry::default().with(log_layer);
+
+    tracing::subscriber::set_global_default(subscriber).map_err(Into::into)
+}