configure threads with env var

utils/frame/remote-externalities/src/lib.rs

@@ -40,13 +40,12 @@ use sp_core::{
 pub use sp_io::TestExternalities;
 use sp_runtime::{traits::Block as BlockT, StateVersion};
 use std::{
-	cmp::{max, min},
+	cmp::max,
 	fs,
 	num::NonZeroUsize,
 	ops::{Deref, DerefMut},
 	path::{Path, PathBuf},
 	sync::Arc,
-	thread,
 };
 use substrate_rpc_client::{rpc_params, BatchRequestBuilder, ChainApi, ClientT, StateApi};
 
@@ -327,7 +326,7 @@ where
 	B::Hash: DeserializeOwned,
 	B::Header: DeserializeOwned,
 {
-	const MAX_PARALLELISM: usize = 4;
+	const DEFAULT_PARALLELISM: usize = 4;
 	const BATCH_SIZE_INCREASE_FACTOR: f32 = 1.10;
 	const BATCH_SIZE_DECREASE_FACTOR: f32 = 0.50;
 	const INITIAL_BATCH_SIZE: usize = 5000;
@@ -338,12 +337,13 @@ where
 	/// Cap the number of threads. Performance improvement beyond a small number of threads is
 	/// negligible, and too many threads can create issues with the HttpClient.
 	fn threads() -> NonZeroUsize {
-		let avaliable = thread::available_parallelism()
-			.unwrap_or(NonZeroUsize::new(1usize).expect("1 is non-zero; qed"))
-			.get();
-		assert!(avaliable > 0, "avaliable parallelism must be greater than 0");
-		return NonZeroUsize::new(min(avaliable, Self::MAX_PARALLELISM))
-			.expect("avaliable is non-zero and MAX_PARRELISM is non-zero; qed")
+		let threads: usize = match std::env::var("TRY_RUNTIME_MAX_THREADS") {
+			Ok(n) => n.parse::<usize>().expect("TRY_RUNTIME_MAX_THREADS must be a number"),
+			Err(_) => Self::DEFAULT_PARALLELISM,
+		};
+		assert!(threads > 0, "TRY_RUNTIME_MAX_THREADS must be greater than 0");
+		dbg!(threads);
+		return NonZeroUsize::new(threads).expect("threads is non-zero; qed")
 	}
 
 	async fn rpc_get_storage(