gisolate

Gevent has tormented me a thousand times, yet I keep coming back for more. This library is proof of that love.

Process isolation for gevent applications. Run any object in a clean subprocess, call its methods transparently via ZMQ IPC.

Why

gevent's monkey.patch_all() replaces stdlib modules globally. Some libraries (database drivers, native async frameworks, etc.) break under monkey-patching. gisolate spawns a clean child process — no monkey-patching — and proxies method calls over ZMQ, so incompatible code runs in isolation while your gevent app stays cooperative.

Install

pip install gisolate

Requires Python 3.12+.

Quick Start

ProcessProxy — persistent child process

Proxy method calls to an object living in an isolated subprocess:

import gevent.monkey
gevent.monkey.patch_all()

from gisolate import ProcessProxy

# Define a factory (must be importable / picklable)
def create_client():
    from some_native_lib import Client
    return Client(host="localhost")

# Option 1: inline
proxy = ProcessProxy.create(create_client, timeout=30)
result = proxy.query("SELECT 1")  # runs in child process
proxy.shutdown()

# Option 2: subclass
class ClientProxy(ProcessProxy):
    client_factory = staticmethod(create_client)
    timeout = 30

with ClientProxy() as proxy:
    result = proxy.query("SELECT 1")

run_in_subprocess — one-shot call

Run a single function in a subprocess and get the result:

from gisolate import run_in_subprocess

def heavy_compute(n):
    return sum(range(n))

result = run_in_subprocess(heavy_compute, args=(10_000_000,), timeout=60)

ProcessBridge — cross-process RPC

ZMQ-based RPC bridge for server/client architectures. Server side uses gevent, client side uses asyncio:

from gisolate import ProcessBridge

# Server (gevent side)
server = ProcessBridge("ipc:///tmp/rpc.sock", mode=ProcessBridge.Mode.SERVER)
server.start()

# Client (asyncio side)
import asyncio

async def main():
    client = ProcessBridge("ipc:///tmp/rpc.sock", mode=ProcessBridge.Mode.CLIENT)
    result = await client.call(lambda x, y: x + y, 3, 4, timeout=5)
    print(result)  # 7
    client.close()

asyncio.run(main())
server.close()

ThreadLocalProxy — per-thread instances

Thread-local proxy using unpatched threading.local for true isolation in gevent.threadpool:

from gisolate import ThreadLocalProxy

proxy = ThreadLocalProxy(create_client)
proxy.query("SELECT 1")  # each real OS thread gets its own instance

Child Process Modes

| patch_kwargs | Child process runtime | |-----------------|----------------------| | None (default) | asyncio event loop | | dict | gevent with patch_all(**patch_kwargs) |

# Child uses asyncio (default)
proxy = ProcessProxy.create(factory)

# Child uses gevent with selective patching
proxy = ProcessProxy.create(factory, patch_kwargs={"thread": False, "os": False})

API Reference

ProcessProxy

• ProcessProxy.create(factory, *, timeout=24, mp_context=None, patch_kwargs=None) — create a proxy without subclassing
• proxy.<method>(*args, **kwargs) — transparently call any method on the remote object
• proxy.restart_process() — kill and restart child process
• proxy.shutdown() — gracefully stop child process
• Supports context manager (with statement)
• Thread-safe: usable from greenlets and native threads

run_in_subprocess(target, args=(), kwargs=None, *, timeout=3600, mp_context=None)

Run a function in an isolated subprocess. Blocks with gevent-safe polling.

ProcessBridge(address, mode)

• bridge.start() — start the bridge (idempotent, returns self)
• bridge.address — IPC address
• await bridge.call(func, *args, timeout=60, **kwargs) — async RPC call (client mode)
• bridge.close() — cleanup resources

ThreadLocalProxy(factory)

Transparent proxy delegating attribute access to a per-thread instance.

ensure_hub_started()

Pre-start the internal gevent hub loop on demand. Idempotent and thread-safe. Called automatically by ProcessProxy, but can be invoked explicitly to control initialization timing.

spawn_on_main_hub(func, *args, **kwargs)

Schedule a function on the main gevent hub without waiting. Thread-safe, fire-and-forget.

ProcessError

Raised when a child process dies or communication fails.

RemoteError

Wrapper for exceptions from the child process that can't be pickled. Preserves the original exception type name and message.

shutdown_hub()

Explicitly stop the internal gevent hub loop. Registered via atexit automatically.

set_default_mp_context(ctx) / get_default_mp_context()

Configure the default multiprocessing context for all proxies (default: "spawn").

Note on multiprocessing and __main__

multiprocessing spawn/forkserver children re-import the caller's __main__ module. If your main.py has top-level side effects (e.g. gevent.monkey.patch_all()), these will re-execute in the child — causing double-patching warnings or import errors.

Best practice: guard monkey-patching behind __name__ and defer heavy imports:

# main.py
if __name__ == "__main__":
    import gevent.monkey
    gevent.monkey.patch_all()

    import my_app
    my_app.run()

Spawn children re-import main.py but skip the __name__ block, avoiding side effects.

License

MIT