fix: Disable tracing by default for crates that cause stack overflows on exit

Cargo.toml

@@ -56,6 +56,7 @@ tower-otel-http-metrics = { version = "0.16.0", features = [
 opentelemetry-resource-detectors = "0.9.0"
 
 [dev-dependencies]
+axum = { version = "^0.8" }
 tokio = { version = "1.43.0", features = ["full"] }
 
 [features]

src/config.rs

@@ -168,7 +168,18 @@ impl Default for ProviderConfig {
 			enabled: false,
 			level: default_level_filter(),
 			general_level: default_level_filter(),
-			dependencies_levels: HashMap::new(),
+			// We have to ignore these specific crates to avoid them emitting traces
+			// after our OTLP collector has been turned off, causing an infinite loop.
+			//
+			// See the issue:  https://github.com/open-telemetry/opentelemetry-rust/issues/2877
+			// See the source of the workaround:
+			// https://github.com/open-telemetry/opentelemetry-rust/blob/v0.31.0/opentelemetry-otlp/examples/basic-otlp/src/main.rs#L69-L86
+			dependencies_levels: HashMap::from([
+				("hyper".to_owned(), LevelFilter(tracing::level_filters::LevelFilter::OFF)),
+				("tonic".to_owned(), LevelFilter(tracing::level_filters::LevelFilter::OFF)),
+				("h2".to_owned(), LevelFilter(tracing::level_filters::LevelFilter::OFF)),
+				("reqwest".to_owned(), LevelFilter(tracing::level_filters::LevelFilter::OFF)),
+			]),
 		}
 	}
 }

tests/otlp.rs

@@ -0,0 +1,50 @@
+// SPDX-FileCopyrightText: 2025 Famedly GmbH (info@famedly.com)
+//
+// SPDX-License-Identifier: Apache-2.0
+
+//! Tests for OTLP
+
+#![allow(clippy::expect_used)]
+
+use axum::routing::post;
+use rust_telemetry::{
+	config::{ExporterConfig, OtelConfig, StdoutLogsConfig},
+	init_otel,
+};
+use url::Url;
+
+/// The current version of the OTLP exporter also induces traces after it's been
+/// shut down, causing a feedback loop which ends in a stack overflow
+///
+/// This test checks that we can start rust-telemetry with an OTLP endpoint
+/// enabled, output a log line, and exit our program without a stack overflow.
+#[tokio::test(flavor = "multi_thread", worker_threads = 2)]
+async fn test_otlp_exporter() {
+	let router = post(|| async { Vec::new() });
+	let listener =
+		tokio::net::TcpListener::bind("127.0.0.1:0").await.expect("Could not bind TCPListener");
+	let endpoint = Url::parse(&format!(
+		"http://{}",
+		listener.local_addr().expect("Failed getting address for listener")
+	))
+	.expect("Failed parsing URL for endpoint");
+	let _mock_otlp = tokio::spawn(async move { axum::serve(listener, router).await });
+
+	let provider_config = Some(rust_telemetry::config::ProviderConfig {
+		enabled: true,
+		general_level: famedly_rust_utils::LevelFilter(tracing::level_filters::LevelFilter::DEBUG),
+		..Default::default()
+	});
+
+	let config = OtelConfig {
+		stdout: Some(StdoutLogsConfig { enabled: true, ..Default::default() }),
+		exporter: Some(ExporterConfig {
+			endpoint: endpoint.into(),
+			logs: provider_config.clone(),
+			traces: provider_config.clone(),
+			..Default::default()
+		}),
+	};
+	let _guard = init_otel!(&config).expect("Error initializing Otel");
+	tracing::info!("Output a line");
+}