fix(node): raise default runtime-cache-size to 8 (upstream default 2 thrashes WASM cache on archive/RPC nodes)

Author: mrq1911

node/src/service.rs

@@ -166,12 +166,23 @@ pub fn new_partial(
 			extra_pages: h as _,
 		});
 
+	// The upstream default runtime cache size (2) is too small for nodes that serve
+	// historical state across runtime upgrades: the hot working set spans several
+	// runtime versions, so a cache of 2 evicts and re-prepares WASM runtimes
+	// constantly and exhausts the instance pool under indexer/RPC load. Treat the
+	// upstream default as "unset" and use 8; honor any explicit operator value.
+	let runtime_cache_size = if config.executor.runtime_cache_size == 2 {
+		8
+	} else {
+		config.executor.runtime_cache_size
+	};
+
 	let executor = WasmExecutor::builder()
 		.with_execution_method(config.executor.wasm_method)
 		.with_onchain_heap_alloc_strategy(heap_pages)
 		.with_offchain_heap_alloc_strategy(heap_pages)
 		.with_max_runtime_instances(config.executor.max_runtime_instances)
-		.with_runtime_cache_size(config.executor.runtime_cache_size)
+		.with_runtime_cache_size(runtime_cache_size)
 		.build();
 
 	let tx_priority_json = if no_tx_priority_override {