Mitigate issues from low RLIMIT_NPROC defaults. (fixes #337)

Signed-off-by: Jason Volk <jason@zemos.net>

src/main/runtime.rs

@@ -16,7 +16,7 @@ use tuwunel_core::{
 	Result, debug, is_true,
 	utils::sys::{
 		compute::{nth_core_available, set_affinity},
-		thread_usage, usage,
+		max_threads,
 	},
 };
 
@@ -50,13 +50,19 @@ pub fn new(args: Option<&Args>) -> Result<Runtime> {
 		.set(args.gc_muzzy)
 		.expect("set GC_MUZZY from program argument");
 
+	let max_blocking_threads = max_threads()
+		.expect("obtained RLIMIT_NPROC or default")
+		.0
+		.saturating_div(3)
+		.clamp(WORKER_MIN, MAX_BLOCKING_THREADS);
+
 	let mut builder = Builder::new_multi_thread();
 	builder
 		.enable_io()
 		.enable_time()
 		.thread_name(WORKER_NAME)
 		.worker_threads(args.worker_threads.max(WORKER_MIN))
-		.max_blocking_threads(MAX_BLOCKING_THREADS)
+		.max_blocking_threads(max_blocking_threads)
 		.thread_keep_alive(Duration::from_secs(WORKER_KEEPALIVE))
 		.global_queue_interval(args.global_event_interval)
 		.event_interval(args.kernel_event_interval)
@@ -110,7 +116,7 @@ pub fn shutdown(server: &Arc<Server>, runtime: Runtime) -> Result {
 		tuwunel_core::event!(LEVEL, ?runtime_metrics, "Final runtime metrics.");
 	}
 
-	if let Ok(resource_usage) = usage() {
+	if let Ok(resource_usage) = tuwunel_core::utils::sys::usage() {
 		tuwunel_core::event!(LEVEL, ?resource_usage, "Final resource usage.");
 	}
 
@@ -208,7 +214,7 @@ fn set_worker_mallctl(_: usize) {}
 )]
 fn thread_stop() {
 	if cfg!(any(tokio_unstable, not(feature = "release_max_log_level")))
-		&& let Ok(resource_usage) = thread_usage()
+		&& let Ok(resource_usage) = tuwunel_core::utils::sys::thread_usage()
 	{
 		tuwunel_core::debug!(?resource_usage, "Thread resource usage.");
 	}

src/main/server.rs

@@ -51,8 +51,9 @@ pub fn new(args: Option<&Args>, runtime: Option<&runtime::Handle>) -> Result<Arc
 	#[cfg(feature = "sentry_telemetry")]
 	let sentry_guard = crate::sentry::init(&config);
 
-	sys::maximize_fd_limit()
-		.expect("Unable to increase maximum soft and hard file descriptor limit");
+	sys::maximize_fd_limit().expect("Unable to increase maximum file descriptor limit");
+
+	sys::maximize_thread_limit().expect("Unable to increase maximum thread count limit");
 
 	let (_old_width, _new_width) = stream::set_width(config.stream_width_default);
 	let (_old_amp, _new_amp) = stream::set_amplification(config.stream_amplification);