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# Worker Pool Management
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Core worker pool lifecycle management for controlling the multi-threaded processing system used by @pnpm/worker.
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## Capabilities
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### Restart Worker Pool
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Restarts the worker pool by finishing current workers and creating a new pool. This is useful for resetting the worker state or applying configuration changes.
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```typescript { .api }
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/**
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 * Restarts the worker pool by finishing current workers and creating a new pool
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 * @returns Promise that resolves when the worker pool has been restarted
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 */
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function restartWorkerPool(): Promise<void>;
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```
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**Usage Example:**
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```typescript
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import { restartWorkerPool } from "@pnpm/worker";
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// Restart the worker pool (e.g., after configuration changes)
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await restartWorkerPool();
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console.log("Worker pool restarted successfully");
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```
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### Finish Workers
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Finishes all active workers in the pool. This should be called before process termination to ensure all workers complete their current tasks gracefully.
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```typescript { .api }
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/**
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 * Finishes all active workers in the pool
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 * @returns Promise that resolves when all workers have finished
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 */
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function finishWorkers(): Promise<void>;
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```
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**Usage Example:**
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```typescript
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import { finishWorkers } from "@pnpm/worker";
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// Gracefully shutdown all workers before process exit
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process.on('SIGTERM', async () => {
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  await finishWorkers();
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  process.exit(0);
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});
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```
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## Implementation Details
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The worker pool is automatically created when needed and uses the following configuration:
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- **Maximum Workers**: Calculated based on `availableParallelism() - 1` or configured via `PNPM_WORKERS` environment variable
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- **Worker Script**: Uses the internal `worker.js` compiled from `worker.ts`
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- **Global Cleanup**: Registers global cleanup handlers for proper worker termination
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- **Worker Pool Library**: Built on `@rushstack/worker-pool` for robust worker management
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The `PNPM_WORKERS` environment variable can be set to control the number of idle CPUs to reserve:
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- If set, workers = `max(2, availableParallelism() - abs(PNPM_WORKERS)) - 1`
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- If not set, workers = `max(1, availableParallelism() - 1)`