Prewarm wasm workers before accepting requests

docs/wasm-runtime-architecture.md

@@ -137,6 +137,11 @@ own import vector, memory/table-base globals, GOT globals and function-table
 slots, then runs relocations, constructors, and request-pointer binding. This
 removes repeated Wasmtime import-type traversal without sharing request state or
 changing core-first, unit-load-order symbol resolution.
+Each FastCGI child initializes its process-local Wasmtime engine after fork and
+before entering the accept loop. This preserves Wasmtime's fork boundary while
+preventing the first request assigned to each worker from paying engine startup.
+Startup duration or failure is written to the service log.
+
 `request_perf()` reports worker module-cache hits and misses and divides a miss
 into artifact lookup, wasm read, custom-section parse, serialized-module
 deserialization or wasm compilation, and immutable import classification. This

src/linux_fastcgi.cpp

@@ -1388,6 +1388,15 @@ void listen_for_connections()
 	server.on_data = &handle_data;
 	server.on_complete = &handle_complete;
 	server.on_cli_complete = &handle_cli_complete;
+	Request startup_context;
+	startup_context.server = &server_state;
+	f64 wasm_start = time_precise();
+	String wasm_error = wasm_backend_start(startup_context);
+	f64 wasm_ms = (time_precise() - wasm_start) * 1000.0;
+	if(wasm_error == "")
+		printf("(P) wasm worker ready: PID %i in %.3f ms\n", getpid(), wasm_ms);
+	else
+		fprintf(stderr, "(!) wasm worker initialization failed: PID %i in %.3f ms: %s\n", getpid(), wasm_ms, wasm_error.c_str());
 	for(;;)
 	{
 		server.process(-1);

src/wasm/backend.cpp

@@ -88,6 +88,11 @@ static String wasm_backend_ensure_started(Request* context)
 	return("");
 }
 
+String wasm_backend_start(Request& request)
+{
+	return(wasm_backend_ensure_started(&request));
+}
+
 static bool wasm_artifact_exists(Request* context, const String& entry_unit)
 {
 	if(entry_unit == "")

src/wasm/backend.h

@@ -10,6 +10,10 @@
 // artifact; handler-agnostic, the caller names the handler.
 bool wasm_backend_should_handle(Request& request, const String& entry_unit);
 
+// Initialize the process-local engine after fork and before the worker accepts
+// requests. Returns "" on success or the retained backend initialization error.
+String wasm_backend_start(Request& request);
+
 // Serve a request through a wasm workspace by invoking a named unit handler —
 // "render", "cli", "websocket", "serve_http", "serve_http:named" — and populate
 // the native Request. Returns "" on success or a collapsed error. The handler is