OTLP export and lifecycle

otel-init creates trace, metric, and log providers. Export is opt-in through an endpoint environment variable.

# Enable all configured signals.
export OTEL_EXPORTER_OTLP_ENDPOINT=http://localhost:4317
export OTEL_EXPORTER_OTLP_PROTOCOL=grpc

Signal-specific endpoints can enable only one signal or override the shared endpoint for that signal:

export OTEL_EXPORTER_OTLP_TRACES_ENDPOINT=http://localhost:4318/v1/traces
export OTEL_EXPORTER_OTLP_TRACES_PROTOCOL=http/protobuf

The corresponding metric and log names are OTEL_EXPORTER_OTLP_METRICS_ENDPOINT / _PROTOCOL and OTEL_EXPORTER_OTLP_LOGS_ENDPOINT / _PROTOCOL. Supported protocol values in this workspace are grpc, http/protobuf (also http/proto), and http/json. A signal-specific protocol takes precedence over OTEL_EXPORTER_OTLP_PROTOCOL; the default is grpc.

When neither the signal-specific endpoint nor the shared endpoint contains a non-blank value, that provider remains local-only. It can still create trace IDs, but it does not construct an exporter or attempt a connection to localhost:4317.

Logger always initializes trace and metric providers. It initializes the log provider only when otel_logs_enabled is true, for example with LOG_OTEL_LOGS_ENABLED=true through the env feature.

Shutdown order

Keep LoggerGuard or OtelGuard alive until application shutdown. Explicit shutdown is available when the application needs to surface provider shutdown errors:

#![allow(unused)]
fn main() {
use tracing_otel::Logger;
fn run() -> anyhow::Result<()> {
let guard = Logger::new("worker").init()?;
tracing::info!("draining work");
guard.shutdown()?;
Ok(())
}
}

LoggerGuard shuts down telemetry providers before releasing its optional non-blocking file writer guard. Dropping a guard also performs cleanup, but an explicit shutdown() is the path that returns provider shutdown errors.