keep web requests off rebuild path

docs/wasm-runtime-architecture.md

@@ -138,12 +138,13 @@ following allocator/relocation call even though no guest loop consumed it.
 
 The proactive compiler and request workers coordinate through a per-unit file
 lock. Unit compilation writes and validates a process-unique temporary wasm
-file, then publishes it with an atomic rename. While another process holds the
-lock for a stale unit, a request may therefore keep using the last complete
-artifact instead of waiting across a transitive rebuild. Once the lock is
-released, normal freshness checks require the new artifact; a failed rebuild
-removes availability and surfaces the compiler error rather than serving the
-old unit indefinitely.
+file, then publishes it with an atomic rename. When proactive compilation is
+enabled, HTTP and WebSocket requests keep using the last complete artifact
+while stale units rebuild in the background; CLI and explicit compile paths
+remain synchronous. A failed rebuild removes availability and surfaces the
+compiler error rather than serving the old unit indefinitely. The per-unit lock
+also keeps concurrent synchronous compilers from waiting across a transitive
+graph when a last complete artifact is available.
 
 ---
 

scripts/test_dependency_invalidation.sh

@@ -11,6 +11,7 @@ if [[ -z "$bin_directory" && -r /etc/uce/settings.cfg ]]; then
 fi
 bin_directory="${bin_directory:-/tmp/uce/work}"
 cache_dir=""
+http_host="${UCE_TEST_HTTP_HOST:-uce.openfu.com}"
 
 cleanup() {
 	rm -rf "$source_dir"
@@ -43,9 +44,28 @@ assert_marker() {
 	fi
 }
 
+http_marker() {
+	curl -fsS -H "Host: $http_host" "http://127.0.0.1/$test_name/parent.uce"
+}
+
 assert_marker parent dependency-marker-a
+if [[ "$(http_marker)" != *"dependency-marker-a"* ]]; then
+	echo "HTTP warm-up did not return dependency-marker-a" >&2
+	exit 1
+fi
 
 sed -i 's/dependency-marker-a/dependency-marker-b/' "$source_dir/child.uce"
+started_at=$(date +%s%N)
+http_during_rebuild=$(http_marker)
+elapsed_ms=$(( ($(date +%s%N) - started_at) / 1000000 ))
+if [[ "$http_during_rebuild" != *"dependency-marker-a"* && "$http_during_rebuild" != *"dependency-marker-b"* ]]; then
+	echo "HTTP rebuild request returned neither complete artifact: $http_during_rebuild" >&2
+	exit 1
+fi
+if (( elapsed_ms >= 2000 )); then
+	echo "HTTP request spent ${elapsed_ms}ms rebuilding a stale artifact" >&2
+	exit 1
+fi
 assert_marker parent dependency-marker-b
 
 # A proactive rebuild owns these same per-unit locks. While it publishes fresh

src/lib/compiler.cpp

@@ -975,6 +975,13 @@ bool compiler_unit_compile_in_progress(Request* context, String file_name)
 	return(false);
 }
 
+bool compiler_request_can_serve_stale_artifact(Request* context)
+{
+	return(context && context->server && !context->resources.is_cli &&
+		to_bool(context->server->config["PROACTIVE_COMPILE_ENABLED"], true) &&
+		float_val(context->server->config["PROACTIVE_COMPILE_CHECK_INTERVAL"]) > 0);
+}
+
 void unit_render(String file_name)
 {
 	unit_render(file_name, *context);

src/lib/compiler.h

@@ -18,6 +18,7 @@ SharedUnit* get_shared_unit(Request* context, String file_name);
 String compiler_error_page_unit(Request* context, String config_key);
 bool compiler_unit_compile_pending(Request* context, String file_name);
 bool compiler_unit_compile_in_progress(Request* context, String file_name);
+bool compiler_request_can_serve_stale_artifact(Request* context);
 String compiler_site_directory(Request* context);
 StringList compiler_scan_site_units(Request* context);
 StringList compiler_list_known_units(Request* context);

src/wasm/backend.cpp

@@ -100,7 +100,7 @@ static bool wasm_artifact_exists(Request* context, const String& entry_unit)
 	// metadata mismatches, which can leave stale wasm with old imports.
 	bool source_missing = false;
 	if(compiler_unit_needs_recompile(context, entry_unit, &source_missing))
-		return(compiler_unit_compile_in_progress(context, entry_unit));
+		return(compiler_request_can_serve_stale_artifact(context) || compiler_unit_compile_in_progress(context, entry_unit));
 	if(source_missing)
 		return(false);
 	return(true);

src/wasm/worker.cpp

@@ -1606,7 +1606,7 @@ private:
 			return(1);
 		}
 
-		if(!file_exists_host(worker.unit_wasm_path(resolved)) || (compiler_unit_needs_recompile(context, resolved, 0) && !compiler_unit_compile_in_progress(context, resolved)))
+		if(!file_exists_host(worker.unit_wasm_path(resolved)) || (compiler_unit_needs_recompile(context, resolved, 0) && !compiler_request_can_serve_stale_artifact(context) && !compiler_unit_compile_in_progress(context, resolved)))
 			get_shared_unit(context, resolved);
 
 		size_t unit_index = 0;