greenletswitch

Greenletswitch is a software framework that provides cooperative multitasking through lightweight execution units called greenlets, enabling fast context switches within a single operating system thread. It is designed to run on runtimes that support stackful coroutine primitives and is inspired by greenlet-like facilities used to implement coroutines and micro-threads in asynchronous applications.

In greenletswitch, a scheduler coordinates a set of greenlets. Each greenlet encapsulates a function and its execution state. Switching occurs via explicit calls to switch, or automatically when the scheduler detects that a greenlet is ready to yield. The scheduler maintains ready and blocked queues, waking greenlets when I/O or timers complete and resuming them in a deterministic order.

The API typically includes a Greenlet type to wrap functions, a run loop or scheduler, and utilities for yielding control, awaiting futures, or interfacing with non-blocking I/O. Programs are structured as a collection of tasks that cooperatively yield at defined points or in response to I/O readiness, enabling high-concurrency patterns without operating-system threads.

Limitations and considerations: greenletswitch operates in a single thread and is not preemptive, so long-running or blocking operations can stall scheduling if not properly managed. It does not bypass the language interpreter's Global Interpreter Lock in Python, so CPU-bound work can limit scalability. Debugging can be more complex than with preemptive parallelism, and integrating with external blocking libraries may require adapters or thread pools.

Use cases include network servers, streaming data pipelines, and simulation tasks that benefit from fast, predictable context switches and fine-grained control over task scheduling. It offers a compatibility layer for porting coroutine-based designs from greenlet-based ecosystems and can be paired with event loops or adapted to work alongside asyncio.