feat: add isolateWorkers support (#4)

* feat: add `isolateWorkers` support

* chore: update

* chore: add test

README.md

@@ -42,6 +42,10 @@ export default ({ a, b }) => {
 
 We have a similar API to Piscina, so for more information, you can read Piscina's detailed [documentation](https://github.com/piscinajs/piscina#piscina---the-nodejs-worker-pool) and apply the same techniques here.
 
+###### Additional Options
+
+- `isolateWorkers`: Default to `false`. Always starts with a fresh worker when running tasks to isolate the environment.
+
 ## Credits
 
 [The Vitest team](https://vitest.dev/) for giving me the chance of creating and maintaing this project for vitest.

src/index.ts

@@ -130,6 +130,7 @@ interface Options {
   workerData?: any
   taskQueue?: TaskQueue
   trackUnmanagedFds?: boolean
+  isolateWorkers?: boolean
 }
 
 interface FilledOptions extends Options {
@@ -774,6 +775,9 @@ class ThreadPool {
     }
     filename = maybeFileURLToPath(filename)
 
+    // Look for a Worker with a minimum number of tasks it is currently running.
+    let workerInfo: WorkerInfo | null = this.workers.findAvailable()
+
     let resolve: (result: any) => void
     let reject: (err: Error) => void
     // eslint-disable-next-line
@@ -788,6 +792,9 @@ class ThreadPool {
       name,
       (err: Error | null, result: any) => {
         this.completed++
+        if (workerInfo && this.options.isolateWorkers) {
+          this._removeWorker(workerInfo)
+        }
         if (err !== null) {
           reject(err)
         } else {
@@ -842,9 +849,6 @@ class ThreadPool {
       return ret
     }
 
-    // Look for a Worker with a minimum number of tasks it is currently running.
-    let workerInfo: WorkerInfo | null = this.workers.findAvailable()
-
     // If we want the ability to abort this task, use only workers that have
     // no running tasks.
     if (workerInfo !== null && workerInfo.currentUsage() > 0 && signal) {
@@ -877,6 +881,7 @@ class ThreadPool {
     taskInfo.started = now
     workerInfo.postTask(taskInfo)
     this._maybeDrain()
+
     return ret
   }
 

test/fixtures/isolated.js

@@ -0,0 +1,3 @@
+let count = 0
+
+export default () => count++

test/simple.test.ts

@@ -156,3 +156,23 @@ test('can destroy pool while tasks are running', async () => {
     /Terminating worker thread/
   )
 })
+
+test('isolateWorkers: false', async () => {
+  const pool = new Tinypool({
+    filename: resolve(__dirname, 'fixtures/isolated.js'),
+    isolateWorkers: false,
+  })
+  expect(await pool.run({})).toBe(1)
+  expect(await pool.run({})).toBe(2)
+  expect(await pool.run({})).toBe(3)
+})
+
+test('isolateWorkers: true', async () => {
+  const pool = new Tinypool({
+    filename: resolve(__dirname, 'fixtures/isolated.js'),
+    isolateWorkers: true,
+  })
+  expect(await pool.run({})).toBe(1)
+  expect(await pool.run({})).toBe(1)
+  expect(await pool.run({})).toBe(1)
+})