ThreadPool

A thread pool is a collection of worker threads that execute tasks from a queue. By reusing a fixed number of threads, it controls concurrency, reduces the overhead of thread creation, and helps manage CPU and memory resources in applications that perform numerous short‑lived tasks.

A typical thread pool consists of a set of worker threads, a task queue, a dispatcher that assigns tasks to idle workers, and lifecycle management to create, execute, and shut down threads. Pool size, queue type, and task rejection policy are common configuration options. The pool may also include mechanisms to monitor progress and handle errors.

When a task is submitted, it is placed in the queue. Idle workers fetch tasks and execute them. If all workers are busy, new tasks wait in the queue until a worker becomes available. On shutdown, in-flight tasks may be completed or canceled according to policy, and the pool releases its resources.

Common pool variants include fixed-size pools, cached pools that grow as needed, single-thread pools for serialized execution, and scheduled pools for delayed or periodic tasks. Many languages provide APIs to submit tasks, obtain futures or promises, and customize rejection behavior.

Benefits of thread pools include improved throughput for many small tasks and controlled resource usage, since the number of concurrent tasks is bounded. Drawbacks include potential contention, the risk that tasks block or deadlock within the pool, and the need for careful shutdown and error handling. Tasks should be designed to be non-blocking or to offload blocking I/O to prevent underutilization of the pool.