passthru worker thread count from env

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

Cargo.toml

@@ -207,14 +207,13 @@ default-features = false
 version = "4.5.21"
 default-features = false
 features = [
-	"std",
 	"derive",
-	"help",
-	#"color", Do we need these?
-	#"unicode",
-	"usage",
+	"env",
 	"error-context",
+	"help",
+	"std",
 	"string",
+	"usage",
 ]
 
 [workspace.dependencies.futures]

src/main/clap.rs

@@ -5,7 +5,9 @@ use std::path::PathBuf;
 use clap::Parser;
 use conduit::{
 	config::{Figment, FigmentValue},
-	err, toml, Err, Result,
+	err, toml,
+	utils::available_parallelism,
+	Err, Result,
 };
 
 /// Commandline arguments
@@ -32,6 +34,10 @@ pub(crate) struct Args {
 	/// Set functional testing modes if available. Ex '--test=smoke'
 	#[arg(long, hide(true))]
 	pub(crate) test: Vec<String>,
+
+	/// Override the tokio worker_thread count.
+	#[arg(long, hide(true), env = "TOKIO_WORKER_THREADS", default_value = available_parallelism().to_string())]
+	pub(crate) worker_threads: usize,
 }
 
 /// Parse commandline arguments into structured data

src/main/main.rs

@@ -9,12 +9,11 @@ mod tracing;
 extern crate conduit_core as conduit;
 
 use std::{
-	cmp,
 	sync::{atomic::Ordering, Arc},
 	time::Duration,
 };
 
-use conduit::{debug_info, error, rustc_flags_capture, utils::available_parallelism, Error, Result};
+use conduit::{debug_info, error, rustc_flags_capture, Error, Result};
 use server::Server;
 use tokio::runtime;
 
@@ -30,7 +29,7 @@ fn main() -> Result<(), Error> {
 		.enable_io()
 		.enable_time()
 		.thread_name(WORKER_NAME)
-		.worker_threads(cmp::max(WORKER_MIN, available_parallelism()))
+		.worker_threads(args.worker_threads.max(WORKER_MIN))
 		.thread_keep_alive(Duration::from_secs(WORKER_KEEPALIVE))
 		.build()
 		.expect("built runtime");