fix(dev): reap every pooled fork on shutdown

Author: danielroe

packages/nuxt-cli/src/dev/index.ts

@@ -27,6 +27,11 @@ class IPC {
   constructor() {
     // only kill process if it is a fork
     if (this.enabled) {
+      // Without a parent there is nobody to reap this process, and it may be
+      // holding the dev server port or the inspector port.
+      process.once('disconnect', () => {
+        process.exit(0)
+      })
       process.once('unhandledRejection', (reason) => {
         this.send({ type: 'nuxt:internal:dev:rejection', message: reason instanceof Error ? reason.toString() : 'Unhandled Rejection' })
         process.exit()

packages/nuxt-cli/src/dev/pool.ts

@@ -5,7 +5,6 @@ import type { NuxtDevContext, NuxtDevIPCMessage } from './utils'
 
 import { fork } from 'node:child_process'
 import process from 'node:process'
-import { isDeno } from 'std-env'
 import { debug } from '../utils/logger'
 
 interface ForkPoolOptions {
@@ -195,7 +194,8 @@ export class ForkPool {
     const wasAlive = fork.state !== 'dead' && !!fork.process && fork.process.exitCode === null
     fork.state = 'dead'
     if (fork.process) {
-      fork.process.kill(signal === 0 && isDeno ? 'SIGTERM' : signal)
+      // signal 0 only probes for liveness, so map the `exit` case onto a real signal
+      fork.process.kill(signal === 0 ? 'SIGTERM' : signal)
     }
     this.removeFork(fork)
 
@@ -223,7 +223,8 @@ export class ForkPool {
   }
 
   private killAll(signal: NodeJS.Signals | number): void {
-    for (const fork of this.pool) {
+    // `killFork` mutates the pool, so iterate over a snapshot
+    for (const fork of [...this.pool]) {
       this.killFork(fork, signal)
     }
   }

packages/nuxt-cli/test/fixtures/fork-pool-entry.mjs

@@ -0,0 +1,6 @@
+import process from 'node:process'
+
+// Node refs the IPC channel while a `message` listener is attached, which is
+// what keeps this stand-in for a warm fork alive after it reports readiness.
+process.on('message', () => {})
+process.send({ type: 'nuxt:internal:dev:fork-ready' })

packages/nuxt-cli/test/unit/fork-pool.spec.ts

@@ -0,0 +1,46 @@
+import type { ChildProcess } from 'node:child_process'
+import { fileURLToPath } from 'node:url'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+
+import { ForkPool } from '../../src/dev/pool'
+
+const devEntry = fileURLToPath(new URL('../fixtures/fork-pool-entry.mjs', import.meta.url))
+
+const pools: ForkPool[] = []
+
+function createPool(poolSize?: number) {
+  globalThis.__nuxt_cli__ = { ...globalThis.__nuxt_cli__, devEntry } as typeof globalThis.__nuxt_cli__
+  const pool = new ForkPool({ rawArgs: [], poolSize, listenOverrides: {} })
+  pools.push(pool)
+  return pool
+}
+
+async function waitForReady(pool: ForkPool, count: number) {
+  await vi.waitFor(() => {
+    expect(pool.getStats().ready).toBe(count)
+  }, { timeout: 20_000, interval: 25 })
+}
+
+afterEach(async () => {
+  for (const pool of pools.splice(0)) {
+    await (pool as unknown as { killAll: (signal: number) => void }).killAll(0)
+  }
+})
+
+describe('forkPool', () => {
+  it('should kill every fork on shutdown', { timeout: 30_000 }, async () => {
+    const pool = createPool(3)
+    pool.startWarming()
+    await waitForReady(pool, 3)
+
+    const processes = (pool as unknown as { pool: Array<{ process: ChildProcess }> }).pool.map(f => f.process)
+    ;(pool as unknown as { killAll: (signal: number) => void }).killAll(0)
+
+    await vi.waitFor(() => {
+      for (const child of processes) {
+        expect(child.killed).toBe(true)
+      }
+    }, { timeout: 10_000, interval: 25 })
+    expect(pool.getStats().total).toBe(0)
+  })
+})