fix: fix worker node cross tasks stealing

Signed-off-by: Jérôme Benoit <jerome.benoit@piment-noir.org>

CHANGELOG.md

@@ -8,6 +8,11 @@ and this project adheres to
 
 ## [Unreleased]
 
+### Fixed
+
+- Avoid worker node cross tasks stealing.
+- Ensure only half the pool worker nodes can steal tasks.
+
 ## [0.1.9] - 2023-12-22
 
 ### Changed

src/pools/abstract-pool.ts

@@ -296,6 +296,14 @@ export abstract class AbstractPool<
  : accumulator,
  0,
  ),
+ ...(this.opts.enableTasksQueue === true &&
+ {
+ stealingWorkerNodes: this.workerNodes.reduce(
+ (accumulator, workerNode) =>
+ workerNode.info.stealing ? accumulator + 1 : accumulator,
+ 0,
+ ),
+ }),
  busyWorkerNodes: this.workerNodes.reduce(
  (accumulator, _workerNode, workerNodeKey) =>
  this.isWorkerNodeBusy(workerNodeKey) ? accumulator + 1 : accumulator,
@@ -1375,6 +1383,10 @@ export abstract class AbstractPool<
  })
  }
 
+ private cannotStealTask(): boolean {
+ return this.workerNodes.length <= 1 || this.info.queuedTasks === 0
+ }
+
  private handleTask(workerNodeKey: number, task: Task<Data>): void {
  if (this.shallExecuteTask(workerNodeKey)) {
  this.executeTask(workerNodeKey, task)
@@ -1387,7 +1399,7 @@ export abstract class AbstractPool<
  if (workerNodeKey === -1) {
  return
  }
- if (this.workerNodes.length <= 1) {
+ if (this.cannotStealTask()) {
  return
  }
  while (this.tasksQueueSize(workerNodeKey) > 0) {
@@ -1481,22 +1493,29 @@ export abstract class AbstractPool<
  event: CustomEvent<WorkerNodeEventDetail>,
  previousStolenTask?: Task<Data>,
  ): void => {
- if (this.workerNodes.length <= 1) {
- return
- }
  const { workerNodeKey } = event.detail
  if (workerNodeKey == null) {
  throw new Error(
- 'WorkerNode event detail workerNodeKey attribute must be defined',
+ 'WorkerNode event detail workerNodeKey property must be defined',
  )
  }
+ if (
+ this.cannotStealTask() || (this.info.stealingWorkerNodes as number) >
+ Math.floor(this.workerNodes.length / 2)
+ ) {
+ if (previousStolenTask != null) {
+ this.getWorkerInfo(workerNodeKey).stealing = false
+ }
+ return
+ }
  const workerNodeTasksUsage = this.workerNodes[workerNodeKey].usage.tasks
  if (
  previousStolenTask != null &&
  workerNodeTasksUsage.sequentiallyStolen > 0 &&
  (workerNodeTasksUsage.executing > 0 ||
  this.tasksQueueSize(workerNodeKey) > 0)
  ) {
+ this.getWorkerInfo(workerNodeKey).stealing = false
  for (
  const taskName of this.workerNodes[workerNodeKey].info
  .taskFunctionNames as string[]
@@ -1511,6 +1530,7 @@ export abstract class AbstractPool<
  )
  return
  }
+ this.getWorkerInfo(workerNodeKey).stealing = true
  const stolenTask = this.workerNodeStealTask(workerNodeKey)
  if (
  this.shallUpdateTaskFunctionWorkerUsage(workerNodeKey) &&
@@ -1556,6 +1576,7 @@ export abstract class AbstractPool<
  const sourceWorkerNode = workerNodes.find(
  (sourceWorkerNode, sourceWorkerNodeKey) =>
  sourceWorkerNode.info.ready &&
+ !sourceWorkerNode.info.stealing &&
  sourceWorkerNodeKey !== workerNodeKey &&
  sourceWorkerNode.usage.tasks.queued > 0,
  )
@@ -1576,7 +1597,10 @@ export abstract class AbstractPool<
  private readonly handleBackPressureEvent = (
  event: CustomEvent<WorkerNodeEventDetail>,
  ): void => {
- if (this.workerNodes.length <= 1) {
+ if (
+ this.cannotStealTask() || (this.info.stealingWorkerNodes as number) >
+ Math.floor(this.workerNodes.length / 2)
+ ) {
  return
  }
  const { workerId } = event.detail
@@ -1596,16 +1620,19 @@ export abstract class AbstractPool<
  if (
  sourceWorkerNode.usage.tasks.queued > 0 &&
  workerNode.info.ready &&
+ !workerNode.info.stealing &&
  workerNode.info.id !== workerId &&
  workerNode.usage.tasks.queued <
  (this.opts.tasksQueueOptions?.size as number) - sizeOffset
  ) {
+ this.getWorkerInfo(workerNodeKey).stealing = true
  const task = sourceWorkerNode.popTask() as Task<Data>
  this.handleTask(workerNodeKey, task)
  this.updateTaskStolenStatisticsWorkerUsage(
  workerNodeKey,
  task.name as string,
  )
+ this.getWorkerInfo(workerNodeKey).stealing = false
  }
  }
  }

src/pools/pool.ts

@@ -71,6 +71,8 @@ export interface PoolInfo {
  readonly workerNodes: number
  /** Pool idle worker nodes. */
  readonly idleWorkerNodes: number
+ /** Pool stealing worker nodes. */
+ readonly stealingWorkerNodes?: number
  /** Pool busy worker nodes. */
  readonly busyWorkerNodes: number
  readonly executedTasks: number

src/pools/worker-node.ts

@@ -196,6 +196,7 @@ export class WorkerNode<Worker extends IWorker, Data = unknown>
  type: getWorkerType(worker) as WorkerType,
  dynamic: false,
  ready: false,
+ stealing: false,
  }
  }
 

src/pools/worker.ts

@@ -146,6 +146,11 @@ export interface WorkerInfo {
  * Ready flag.
  */
  ready: boolean
+ /**
+ * Stealing flag.
+ * This flag is set to `true` when worker node is stealing tasks from another worker node.
+ */
+ stealing: boolean
  /**
  * Task function names.
  */

tests/pools/abstract-pool.test.mjs

@@ -1028,6 +1028,7 @@ Deno.test({
  type: WorkerTypes.web,
  dynamic: false,
  ready: true,
+ stealing: false,
  })
  }
  await pool.destroy()
@@ -1046,6 +1047,7 @@ Deno.test({
  type: WorkerTypes.web,
  dynamic: false,
  ready: true,
+ stealing: false,
  })
  }
  await pool.destroy()
@@ -1447,7 +1449,7 @@ Deno.test({
  stub(
  pool,
  'hasBackPressure',
- returnsNext(Array(5).fill(true)),
+ returnsNext(Array(7).fill(true)),
  )
  expect(pool.emitter.eventNames()).toStrictEqual([])
  const promises = new Set()
@@ -1476,6 +1478,7 @@ Deno.test({
  maxSize: expect.any(Number),
  workerNodes: expect.any(Number),
  idleWorkerNodes: expect.any(Number),
+ stealingWorkerNodes: expect.any(Number),
  busyWorkerNodes: expect.any(Number),
  executedTasks: expect.any(Number),
  executingTasks: expect.any(Number),
@@ -1485,7 +1488,7 @@ Deno.test({
  stolenTasks: expect.any(Number),
  failedTasks: expect.any(Number),
  })
- assertSpyCalls(pool.hasBackPressure, 5)
+ assertSpyCalls(pool.hasBackPressure, 7)
  pool.hasBackPressure.restore()
  await pool.destroy()
  },

tests/pools/worker-node.test.mjs

@@ -120,6 +120,7 @@ Deno.test({
  type: WorkerTypes.web,
  dynamic: false,
  ready: false,
+ stealing: false,
  })
  expect(threadWorkerNode.usage).toStrictEqual({
  tasks: {

tests/worker/thread-worker.test.mjs

@@ -32,6 +32,9 @@ Deno.test('Thread worker test suite', async (t) => {
  return 2
  }
  const worker = new ThreadWorker({ fn1, fn2 })
+ worker.port = {
+ postMessage: stub(() => {}),
+ }
  expect(worker.removeTaskFunction(0, fn1)).toStrictEqual({
  status: false,
  error: new TypeError('name parameter is not a string'),
@@ -40,9 +43,6 @@ Deno.test('Thread worker test suite', async (t) => {
  status: false,
  error: new TypeError('name parameter is an empty string'),
  })
- worker.port = {
- postMessage: stub(() => {}),
- }
  expect(worker.taskFunctions.get(DEFAULT_TASK_NAME)).toBeInstanceOf(
  Function,
  )
@@ -85,17 +85,12 @@ Deno.test('Thread worker test suite', async (t) => {
  })
 
  await t.step(
- 'Verify worker invokes the postMessage() method on port property',
+ 'Verify that sendToMainWorker() method invokes the port property postMessage() method',
  () => {
- class SpyWorker extends ThreadWorker {
- constructor(fn) {
- super(fn)
- this.port = {
- postMessage: stub(() => {}),
- }
- }
+ const worker = new ThreadWorker(() => {})
+ worker.port = {
+ postMessage: stub(() => {}),
  }
- const worker = new SpyWorker(() => {})
  worker.sendToMainWorker({ ok: 1 })
  assertSpyCalls(worker.port.postMessage, 1)
  worker.port.postMessage.restore()