artificialturf

Provides greenlet emulation for Jython using normal threads.

At first glance, this may seem to be of no value. After all, isn't the point of greenlets is to avoid the overhead of regular threads? But there are a number of reasons that make this reasonable:

• Experience has shown that one can readily run 1000s or 10000s of threads on the JVM using Linux. Close control of stack size allocations might make this work for certain cases.

• Lightweight threads are available for the JVM using Quasar. (Such lightweight threads, like greenlets, save the callstack to the heap when the greenlet is not active.) To really make use of this support will require supporting Python bytecode in Jython, given that a call to switch cannot be reliably statically identified, unlike yield in normal Python coroutines. Such support in Jython for Python bytecode is a feature that is needed for other reasons, including support for invokedynamic, so it's reasonable to assume it will be delivered at some point.

• Certain codebases are migrating away from greenlet/eventlet, such as OpenStack, in favor of externally manage async support, namely asyncio.

It's this last point that motivated this development, so that it may be a bridge to such support for running such interesting codebases on Jython.