forsake

forsake is a Python library to quickly spawn copies of Python processes that otherwise take a long time to load.

This library was originally developed for SageMath which typically takes 2s to start. With this library the startup time can be cut down to about 100ms.

The idea is to start the expensive process once and then use the fork system call to spawn more copies quickly. Since copies then have their stdin, stdout, stderr attached to the calling terminal, it appears is if the process were a child of the calling shell.

Not all operating systems do implement fork. In particular, we cannot use this approach to quickly clone a process on Windows. It should work fine on all Unixes such as Linux and macOS. (But it does not actually work on macOS, see #6.)

Installation

pip install forsake

Performance

With the approach here the startup time of a process can be cut down to the startup time of Python + the time needed to import some basic networking modules. Typically, to about 100ms.

Things could be sped up much further by implementing the client process in C or C++.

Security

The forking server is listening on a Unix socket which is created securely. To our knowledge there are no security problems with this approach.

Examples

forsake comes with a command line interface forsake-server and forsake-client. These were written as demo applications. For production use, you probably want to write a specialized command line interface that suits your use case.

Note that all the example files used below can be found in the demo/ directory.

Spawn a SageMath Executor

On modern systems, the SageMath startup takes about 2 seconds. The time is mostly spent importing lots of Python libraries that get pulled in by sage.all even if only a very small fraction of these libraries is used.

Here, we create a forking server that preloads sage.all and then execute a computation in a fresh fork of this server when a client requests it:

$ cat demo/sage/computation.py
from sage.all import ZZ
print(ZZ(1337).factor())
$ forsake-server --socket /tmp/forsake.socket --warmup demo/sage/executor.py  # this command hangs while it is waiting for connections
$ time sage demo/sage/computation.py
7 * 191  # takes about 2s
$ forsake-client --socket /tmp/forsake.socket --startup demo/sage/computation.py
7 * 191  # takes about 100ms

Spawn a SageMath REPL

$ forsake-server --socket /tmp/forsake.socket --warmup demo/sage/repl-warmup.py  # this command hangs whil it is waiting for connections
$ forsake-client --socket /tmp/forsake.socket --startup demo/sage/repl-startup.py
sage: 1337.factor()
7 * 191

Development

Any recent version of Python should work to develop forsake. The few required dependencies can be conveniently installed with mamba:

mamba env create -f environment.yml
mamba activate forsake-dev

To install a development version of forsake, run pip install -e . in this directory.

To run the test suite, run pytest in this directy.