Rotate PHP runtime after runtime crash (#1628)

## Motivation for the change, related issues

We want Playground to be able be more resilient in the face of PHP
crashes. This PR rotates the PHP runtime when a PHP runtime crash is
detected.

Fixes #1453

## Testing Instructions (or ideally a Blueprint)

- Added new unit test
- CI

packages/php-wasm/node/src/test/rotate-php-runtime.spec.ts

@@ -66,7 +66,7 @@ describe('rotatePHPRuntime()', () => {
 		expect(recreateRuntimeSpy).toHaveBeenCalledTimes(2);
 	}, 30_000);
 
-	it('Should stop rotating after the cleanup handler is called', async () => {
+	it('Should not rotate after the cleanup handler is called, even if max requests is reached', async () => {
 		const recreateRuntimeSpy = vitest.fn(recreateRuntime);
 		const php = new PHP(await recreateRuntimeSpy());
 		const cleanup = rotatePHPRuntime({
@@ -88,6 +88,72 @@ describe('rotatePHPRuntime()', () => {
 		expect(recreateRuntimeSpy).toHaveBeenCalledTimes(2);
 	}, 30_000);
 
+	it('Should recreate the PHP runtime after a PHP runtime crash', async () => {
+		const recreateRuntimeSpy = vitest.fn(recreateRuntime);
+		const php = new PHP(await recreateRuntimeSpy());
+		rotatePHPRuntime({
+			php,
+			cwd: '/test-root',
+			recreateRuntime: recreateRuntimeSpy,
+			maxRequests: 1234,
+		});
+		// Cause a PHP runtime rotation due to error
+		await php.dispatchEvent({
+			type: 'request.error',
+			error: new Error('mock error'),
+			source: 'php-wasm',
+		});
+		expect(recreateRuntimeSpy).toHaveBeenCalledTimes(2);
+	}, 30_000);
+
+	it('Should not recreate the PHP runtime after a PHP fatal', async () => {
+		const recreateRuntimeSpy = vitest.fn(recreateRuntime);
+		const php = new PHP(await recreateRuntimeSpy());
+		rotatePHPRuntime({
+			php,
+			cwd: '/test-root',
+			recreateRuntime: recreateRuntimeSpy,
+			maxRequests: 1234,
+		});
+		// Trigger error with no `source`
+		await php.dispatchEvent({
+			type: 'request.error',
+			error: new Error('mock error'),
+		});
+		// Trigger error with request `source`
+		await php.dispatchEvent({
+			type: 'request.error',
+			error: new Error('mock error'),
+			source: 'request',
+		});
+		expect(recreateRuntimeSpy).toHaveBeenCalledTimes(1);
+	}, 30_000);
+
+	it('Should not rotate after the cleanup handler is called, even if there is a PHP runtime error', async () => {
+		const recreateRuntimeSpy = vitest.fn(recreateRuntime);
+		const php = new PHP(await recreateRuntimeSpy());
+		const cleanup = rotatePHPRuntime({
+			php,
+			cwd: '/test-root',
+			recreateRuntime: recreateRuntimeSpy,
+			maxRequests: 1,
+		});
+		// Rotate the PHP runtime
+		await php.run({ code: `` });
+		expect(recreateRuntimeSpy).toHaveBeenCalledTimes(2);
+
+		cleanup();
+
+		// No further rotation should happen
+		php.dispatchEvent({
+			type: 'request.error',
+			error: new Error('mock error'),
+			source: 'php-wasm',
+		});
+
+		expect(recreateRuntimeSpy).toHaveBeenCalledTimes(2);
+	}, 30_000);
+
 	it('Should hotswap the PHP runtime from 8.2 to 8.3', async () => {
 		let nbCalls = 0;
 		const recreateRuntimeSpy = vitest.fn(() => {

packages/php-wasm/universal/src/lib/rotate-php-runtime.ts

@@ -1,4 +1,5 @@
 import { PHP } from './php';
+import { PHPEvent } from './universal-php';
 
 export interface RotateOptions {
 	php: PHP;
@@ -37,22 +38,37 @@ export function rotatePHPRuntime({
 	 */
 	maxRequests = 400,
 }: RotateOptions) {
-	let handledCalls = 0;
+	let runtimeRequestCount = 0;
 	async function rotateRuntime() {
-		if (++handledCalls < maxRequests) {
-			return;
-		}
-		handledCalls = 0;
-
 		const release = await php.semaphore.acquire();
 		try {
 			php.hotSwapPHPRuntime(await recreateRuntime(), cwd);
+
+			// A new runtime has handled zero requests.
+			runtimeRequestCount = 0;
 		} finally {
 			release();
 		}
 	}
-	php.addEventListener('request.end', rotateRuntime);
+
+	async function rotateRuntimeAfterMaxRequests() {
+		if (++runtimeRequestCount < maxRequests) {
+			return;
+		}
+		await rotateRuntime();
+	}
+
+	async function rotateRuntimeForPhpWasmError(event: PHPEvent) {
+		if (event.type === 'request.error' && event.source === 'php-wasm') {
+			await rotateRuntime();
+		}
+	}
+
+	php.addEventListener('request.error', rotateRuntimeForPhpWasmError);
+	php.addEventListener('request.end', rotateRuntimeAfterMaxRequests);
+
 	return function () {
-		php.removeEventListener('request.end', rotateRuntime);
+		php.removeEventListener('request.error', rotateRuntimeForPhpWasmError);
+		php.removeEventListener('request.end', rotateRuntimeAfterMaxRequests);
 	};
 }