perf(logger): stop building a throwaway pino root per child (#2132)

packages/logger/src/Logger.ts

@@ -111,8 +111,13 @@ function createPinoLogger(serviceName: string, options: LoggerOptions = {}): Pin
 export class Logger {
 	private logger: PinoLogger;
 
-	constructor(serviceName: string, options: LoggerOptions = {}) {
-		this.logger = createPinoLogger(serviceName, options);
+	constructor(serviceName: string, options?: LoggerOptions);
+	constructor(pinoLogger: PinoLogger);
+	constructor(serviceNameOrPinoLogger: string | PinoLogger, options: LoggerOptions = {}) {
+		this.logger =
+			typeof serviceNameOrPinoLogger === 'string'
+				? createPinoLogger(serviceNameOrPinoLogger, options)
+				: serviceNameOrPinoLogger;
 	}
 
 	getPinoLogger(): PinoLogger {
@@ -124,9 +129,7 @@ export class Logger {
 	}
 
 	static createWithLogger(logger: PinoLogger): Logger {
-		const childLogger = new Logger('', {});
-		childLogger.setPinoLogger(logger);
-		return childLogger;
+		return new Logger(logger);
 	}
 
 	trace(obj: Record<string, unknown>, msg?: string): void;

packages/logger/src/__tests__/Logger.test.ts

@@ -0,0 +1,39 @@
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+import {createLogger, Logger} from '@fluxer/logger/src/Logger';
+import pino, {type Logger as PinoLogger} from 'pino';
+import {afterEach, describe, expect, it, vi} from 'vitest';
+
+function readDestination(logger: PinoLogger): unknown {
+	return (logger as unknown as Record<symbol, unknown>)[pino.symbols.streamSym];
+}
+
+describe('Logger.child', () => {
+	afterEach(() => {
+		vi.restoreAllMocks();
+		vi.unstubAllEnvs();
+	});
+
+	it('shares the parent destination instead of opening a new one', () => {
+		const parent = createLogger('logger-test', {environment: 'production'});
+		const child = parent.child({logger: 'ChildService'});
+		expect(child).toBeInstanceOf(Logger);
+		expect(readDestination(child.pino)).toBe(readDestination(parent.pino));
+	});
+
+	it('does not construct a throwaway pino root logger', () => {
+		vi.stubEnv('FLUXER_ENV', 'production');
+		const parent = createLogger('logger-test', {environment: 'production'});
+		const destinationSpy = vi.spyOn(pino, 'destination');
+		const child = parent.child({logger: 'ChildService'});
+		expect(destinationSpy).not.toHaveBeenCalled();
+		expect(child.pino.bindings()['logger']).toBe('ChildService');
+	});
+
+	it('keeps the parent bindings on the child', () => {
+		const parent = createLogger('logger-test', {environment: 'production'});
+		const child = parent.child({logger: 'ChildService'});
+		expect(child.pino.bindings()['service']).toBe('logger-test');
+		expect(child.pino.level).toBe(parent.pino.level);
+	});
+});