fix(dev): keep warming the pool once the app is served by a fork

Author: danielroe

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

@@ -60,6 +60,10 @@ export class ForkPool {
 }
 
 asyncgetFork(context: NuxtDevContext,onMessage?: (message: NuxtDevIPCMessage)=>void): Promise<()=>Promise<void>>{
+// Once the app is served by a fork, file changes are no longer visible to
+// this process, so a restart is the only signal left that more may follow.
+this.warming=true
+
 // Try to get a ready fork from the pool
 constreadyFork=this.pool.find(f=>f.state==='ready')
 
@@ -70,10 +74,7 @@ export class ForkPool {
 }
 awaitthis.sendContext(readyFork.process,context)
 
-// Start warming a replacement fork
-if(this.warming){
-this.warmFork()
-}
+this.warmFork()
 
 return()=>this.killFork(readyFork)
 }
@@ -88,10 +89,7 @@ export class ForkPool {
 }
 awaitthis.sendContext(warmingFork.process,context)
 
-// Start warming a replacement fork
-if(this.warming){
-this.warmFork()
-}
+this.warmFork()
 
 return()=>this.killFork(warmingFork)
 }
@@ -107,6 +105,8 @@ export class ForkPool {
 }
 awaitthis.sendContext(coldFork.process,context)
 
+this.warmFork()
+
 return()=>this.killFork(coldFork)
 }
 
@@ -120,6 +120,11 @@ export class ForkPool {
 }
 
 privatewarmFork(): void{
+constidle=this.pool.filter(f=>f.state==='warming'||f.state==='ready').length
+if(idle>=this.poolSize){
+return
+}
+
 constfork=this.createFork()
 fork.ready.then(()=>{
 if(fork.state==='warming'){

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

@@ -47,6 +47,21 @@ describe('forkPool', () => {
 },{timeout: 10_000,interval: 25})
 })
 
+it('should keep the pool warm after handing out a fork',{timeout: 30_000},async()=>{
+constpool=createPool()
+awaitpool.getFork({cwd: '/some/project',args: {}})
+awaitwaitForReady(pool,1)
+expect(pool.getStats().active).toBe(1)
+})
+
+it('should never warm a fork when the pool is disabled',{timeout: 30_000},async()=>{
+constpool=createPool(0)
+pool.startWarming()
+awaitpool.getFork({cwd: '/some/project',args: {}})
+awaitnewPromise(resolve=>setTimeout(resolve,1000))
+expect(pool.getStats()).toMatchObject({total: 1,active: 1,ready: 0,warming: 0})
+})
+
 it('should kill every fork on shutdown',{timeout: 30_000},async()=>{
 constpool=createPool(3)
 pool.startWarming()