perf(core): Introduce decorator to report slow method calls (#17729)

packages/@n8n/decorators/src/index.ts

@@ -9,3 +9,4 @@ export * from './pubsub';
 export { Redactable } from './redactable';
 export * from './shutdown';
 export * from './module/module-metadata';
+export { Timed, TimedOptions } from './timed';

packages/@n8n/decorators/src/timed.ts

@@ -0,0 +1,42 @@
+export interface TimedOptions {
+	/** Duration (in ms) above which to log a warning. Defaults to `100`. */
+	threshold?: number;
+	/** Whether to include method parameters in the log. Defaults to `false`. */
+	logArgs?: boolean;
+}
+
+interface Logger {
+	warn(message: string, meta?: object): void;
+}
+
+/**
+ * Factory to create decorators to warn when method calls exceed a duration threshold.
+ */
+export const Timed =
+	(logger: Logger, msg = 'Slow method call') =>
+	(options: TimedOptions = {}): MethodDecorator =>
+	(_target, propertyKey, descriptor: PropertyDescriptor) => {
+		const originalMethod = descriptor.value as (...args: unknown[]) => unknown;
+		const thresholdMs = options.threshold ?? 100;
+		const logArgs = options.logArgs ?? false;
+
+		descriptor.value = async function (...args: unknown[]) {
+			const methodName = `${this.constructor.name}.${String(propertyKey)}`;
+			const start = performance.now();
+			const result = await originalMethod.apply(this, args);
+			const durationMs = performance.now() - start;
+
+			if (durationMs > thresholdMs) {
+				logger.warn(msg, {
+					method: methodName,
+					durationMs: Math.round(durationMs),
+					thresholdMs,
+					params: logArgs ? args : '[hidden]',
+				});
+			}
+
+			return result;
+		};
+
+		return descriptor;
+	};