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Feature: optional rate limiter on concurrent sitemap functions execut…
…ed (#62)
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,91 @@ | ||
| import { RateLimiter } from '../rate-limiter'; | ||
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| describe('RateLimiter', () => { | ||
| it('should not allow more than the rate limit to run concurrently', async () => { | ||
| const limit = new RateLimiter(3); | ||
| let activeTasks = 0; | ||
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| const increaseActive = () => { | ||
| activeTasks++; | ||
| }; | ||
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| const decreaseActive = () => { | ||
| activeTasks--; | ||
| limit.free(); | ||
| }; | ||
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| const tasks = Array(5) | ||
| .fill(null) | ||
| .map(async () => { | ||
| await limit.allocate(); | ||
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| increaseActive(); | ||
| expect(activeTasks).toBeLessThanOrEqual(3); | ||
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| // Mock task duration (randomness to affect completion order) | ||
| await new Promise(resolve => | ||
| setTimeout(resolve, 500 + 500 * Math.random()) | ||
| ); | ||
| decreaseActive(); | ||
| }); | ||
| await Promise.all(tasks); | ||
| }); | ||
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| it('should queue tasks and execute them in order', async () => { | ||
| const limit = new RateLimiter(1); | ||
| const taskOrder: number[] = []; | ||
| const mockTask = async (id: number) => { | ||
| await limit.allocate(); | ||
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| // Make each task successively longer to ensure execution completion order | ||
| await new Promise(resolve => setTimeout(resolve, 100)); | ||
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| taskOrder.push(id); | ||
| limit.free(); | ||
| }; | ||
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| const tasks = [1, 2, 3, 4].map(id => mockTask(id)); | ||
| await Promise.all(tasks); | ||
| expect(taskOrder).toEqual([1, 2, 3, 4]); // Ensure tasks are executed in the expected order | ||
| expect(limit.getProcessing()).toEqual(0); | ||
| expect(limit.getWaiting()).toEqual(0); | ||
| }); | ||
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| it('ensure too many tasks never run at once', async () => { | ||
| const maxConcurrent = 20; | ||
| const limit = new RateLimiter(maxConcurrent); | ||
| const mockTask = async () => { | ||
| await limit.allocate(); | ||
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| expect(limit.getProcessing()).toBeLessThanOrEqual(maxConcurrent); | ||
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| // Mock task duration (randomness to affect completion order) | ||
| await new Promise(resolve => setTimeout(resolve, 500 * Math.random())); | ||
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| expect(limit.getProcessing()).toBeLessThanOrEqual(maxConcurrent); | ||
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| limit.free(); | ||
| }; | ||
| await Promise.all( | ||
| Array(100) | ||
| .fill(0) | ||
| .map(() => mockTask()) | ||
| ); | ||
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| expect(limit.getProcessing()).toEqual(0); | ||
| expect(limit.getWaiting()).toEqual(0); | ||
| }); | ||
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| it('should handle rapid calls to free correctly', async () => { | ||
| const limit = new RateLimiter(1); | ||
| const mockTask = async () => { | ||
| await limit.allocate(); | ||
| limit.free(); | ||
| limit.free(); // Intentional rapid call to free | ||
| }; | ||
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| await Promise.all([mockTask(), mockTask()]); | ||
| expect(limit.getProcessing()).toEqual(0); | ||
| expect(limit.getWaiting()).toEqual(0); | ||
| }); | ||
| }); |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,50 @@ | ||
| /** | ||
| * Usage: | ||
| * const limit = new RateLimiter(3); | ||
| * Promise.all(arr.map(async x => { | ||
| * await limit.allocate(); // waits until there are less than three active | ||
| * await longTask(x); | ||
| * limit.free(); // mark the task as done, allowing another to start | ||
| * })) | ||
| */ | ||
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| export class RateLimiter { | ||
| rate: number; | ||
| queue: Array<() => void>; | ||
| active: number; | ||
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| constructor(rate: number) { | ||
| this.rate = rate; | ||
| this.queue = []; | ||
| this.active = 0; | ||
| } | ||
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| allocate(): Promise<void> { | ||
| return new Promise(res => { | ||
| if (this.active < this.rate) { | ||
| this.active++; | ||
| res(); | ||
| } else { | ||
| this.queue.push(res); | ||
| } | ||
| }); | ||
| } | ||
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| free(): void { | ||
| const first = this.queue.shift(); | ||
| if (first) { | ||
| // Don't change activity count | ||
| // just substitute the finished work with new work | ||
| first(); | ||
| } else { | ||
| this.active = Math.max(0, this.active - 1); | ||
| } | ||
| } | ||
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| getProcessing(): number { | ||
| return this.active; | ||
| } | ||
| getWaiting(): number { | ||
| return this.queue.length; | ||
| } | ||
| } |