Init something which kinda works

.gitignore

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+# Created by https://www.toptal.com/developers/gitignore/api/python
+# Edit at https://www.toptal.com/developers/gitignore?templates=python
+
+### Python ###
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# C extensions
+*.so
+
+# Distribution / packaging
+.Python
+build/
+develop-eggs/
+dist/
+downloads/
+eggs/
+.eggs/
+lib/
+lib64/
+parts/
+sdist/
+var/
+wheels/
+share/python-wheels/
+*.egg-info/
+.installed.cfg
+*.egg
+MANIFEST
+
+# PyInstaller
+#  Usually these files are written by a python script from a template
+#  before PyInstaller builds the exe, so as to inject date/other infos into it.
+*.manifest
+*.spec
+
+# Installer logs
+pip-log.txt
+pip-delete-this-directory.txt
+
+# Unit test / coverage reports
+htmlcov/
+.tox/
+.nox/
+.coverage
+.coverage.*
+.cache
+nosetests.xml
+coverage.xml
+*.cover
+*.py,cover
+.hypothesis/
+.pytest_cache/
+cover/
+
+# Translations
+*.mo
+*.pot
+
+# Django stuff:
+*.log
+local_settings.py
+db.sqlite3
+db.sqlite3-journal
+
+# Flask stuff:
+instance/
+.webassets-cache
+
+# Scrapy stuff:
+.scrapy
+
+# Sphinx documentation
+docs/_build/
+
+# PyBuilder
+.pybuilder/
+target/
+
+# Jupyter Notebook
+.ipynb_checkpoints
+
+# IPython
+profile_default/
+ipython_config.py
+
+# pyenv
+#   For a library or package, you might want to ignore these files since the code is
+#   intended to run in multiple environments; otherwise, check them in:
+# .python-version
+
+# pipenv
+#   According to pypa/pipenv#598, it is recommended to include Pipfile.lock in version control.
+#   However, in case of collaboration, if having platform-specific dependencies or dependencies
+#   having no cross-platform support, pipenv may install dependencies that don't work, or not
+#   install all needed dependencies.
+#Pipfile.lock
+
+# poetry
+#   Similar to Pipfile.lock, it is generally recommended to include poetry.lock in version control.
+#   This is especially recommended for binary packages to ensure reproducibility, and is more
+#   commonly ignored for libraries.
+#   https://python-poetry.org/docs/basic-usage/#commit-your-poetrylock-file-to-version-control
+#poetry.lock
+
+# pdm
+#   Similar to Pipfile.lock, it is generally recommended to include pdm.lock in version control.
+#pdm.lock
+#   pdm stores project-wide configurations in .pdm.toml, but it is recommended to not include it
+#   in version control.
+#   https://pdm.fming.dev/#use-with-ide
+.pdm.toml
+
+# PEP 582; used by e.g. github.com/David-OConnor/pyflow and github.com/pdm-project/pdm
+__pypackages__/
+
+# Celery stuff
+celerybeat-schedule
+celerybeat.pid
+
+# SageMath parsed files
+*.sage.py
+
+# Environments
+.env
+.venv
+env/
+venv/
+ENV/
+env.bak/
+venv.bak/
+
+# Spyder project settings
+.spyderproject
+.spyproject
+
+# Rope project settings
+.ropeproject
+
+# mkdocs documentation
+/site
+
+# mypy
+.mypy_cache/
+.dmypy.json
+dmypy.json
+
+# Pyre type checker
+.pyre/
+
+# pytype static type analyzer
+.pytype/
+
+# Cython debug symbols
+cython_debug/
+
+# PyCharm
+#  JetBrains specific template is maintained in a separate JetBrains.gitignore that can
+#  be found at https://github.com/github/gitignore/blob/main/Global/JetBrains.gitignore
+#  and can be added to the global gitignore or merged into this file.  For a more nuclear
+#  option (not recommended) you can uncomment the following to ignore the entire idea folder.
+#.idea/
+
+### Python Patch ###
+# Poetry local configuration file - https://python-poetry.org/docs/configuration/#local-configuration
+poetry.toml
+
+# ruff
+.ruff_cache/
+
+# LSP config files
+pyrightconfig.json
+
+# End of https://www.toptal.com/developers/gitignore/api/python
+
+runusb.sock
+global-metadata.json
+log.txt

main.py

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+import time
+from itertools import count
+
+for i in count():
+    print("Still running", i)
+    time.sleep(1)

metadata.json

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+{
+    "foo": "bar"
+}

runusb.py

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+import subprocess
+import threading
+from pathlib import Path
+import logging
+import os
+import time
+import atexit
+import json
+import zmq
+
+GLOBAL_METADATA = Path.cwd() / "global-metadata.json"
+ZMQ_SOCKET = Path.cwd() / "runusb.sock"
+
+def get_zmq_publisher():
+    context = zmq.Context()
+    socket = context.socket(zmq.PUB)
+    socket.bind("ipc://" + str(ZMQ_SOCKET))
+    return socket
+
+def get_zmq_subscriber(topic: str):
+    context = zmq.Context()
+    socket = context.socket(zmq.SUB)
+    socket.setsockopt_string(zmq.SUBSCRIBE, topic)
+    socket.connect("ipc://" + str(ZMQ_SOCKET))
+    return socket
+
+class UserCodeSupervisor(threading.Thread):
+    def __init__(self, process: subprocess.Popen, mountpoint: Path):
+        super().__init__()
+        self.process = process
+        self.logfile = mountpoint / "log.txt"
+        self.zmq_publisher = get_zmq_publisher()
+
+    def run(self):
+        with self.logfile.open(mode="w") as log_file:
+            while self.process.returncode is None:
+                stdout_data = self.process.stdout.readline()
+                print(stdout_data, end="")
+                log_file.write(stdout_data)
+                log_file.flush()
+
+                self.zmq_publisher.send_multipart([b"log", stdout_data.encode()])
+
+                self.process.poll()
+
+
+
+class RunUSBRegistry:
+    process: subprocess.Popen | None = None
+    usercode_dir: Path | None = None
+
+    def __init__(self):
+        self.lock = threading.Lock()
+        self.metadata = {}
+        self.update_metadata({})
+
+    def start_user_code(self, mountpoint: Path):
+        self.usercode_dir = mountpoint
+
+        entrypoint = mountpoint / "main.py"
+        self.process = subprocess.Popen(
+            ["python3", entrypoint],
+            env={
+                **os.environ,
+                "PYTHONUNBUFFERED": "1",
+                "METADATA_FILE": str(GLOBAL_METADATA)
+            },
+            cwd=mountpoint,
+            stdin=subprocess.DEVNULL,
+            stdout=subprocess.PIPE,
+            stderr=subprocess.STDOUT,
+            universal_newlines=True,
+        )
+
+        UserCodeSupervisor(self.process, mountpoint).start()
+
+    def restart_user_code(self):
+        mountpoint = self.usercode_dir
+
+        self.stop_user_code()
+        self.start_user_code(mountpoint)
+
+    def stop_user_code(self):
+        self.process.terminate()
+
+        try:
+            self.process.wait(timeout=5)
+        except subprocess.TimeoutExpired:
+            pass
+
+        if self.process.poll() is not None:
+            self.process.kill()
+
+        # Remove the reference
+        self.process = None
+        self.usercode_dir = None
+
+    def handle_metadata_file(self, metadata_file: Path):
+        with metadata_file.open(mode="r") as f:
+            self.metadata = json.load(f)
+
+        # Notify with a blank update, as everything is new
+        self.update_metadata({})
+
+    def update_metadata(self, new_metadata: dict):
+        self.metadata.update(new_metadata)
+
+        with GLOBAL_METADATA.open("w") as f:
+            json.dump(self.metadata, f)
+
+    def __enter__(self):
+        self.lock.acquire()
+
+    def __exit__(self, *args):
+        self.lock.release()
+
+    def close(self):
+        self.stop_user_code()
+
+
+class BusHandler(threading.Thread):
+    def __init__(self, registry: RunUSBRegistry):
+        super().__init__()
+        self.registry = registry
+        self.zmq_subscriber = get_zmq_subscriber("")
+
+    def run(self):
+        while True:
+            topic, message = self.zmq_subscriber.recv_multipart()
+
+            topic = topic.decode()
+            message = message.decode()
+
+            # if topic == "log":
+            #     continue
+
+            if topic == "restart":
+                with registry:
+                    registry.restart_user_code()
+
+            else:
+                print("Ignoring message with topic", topic, message.strip())
+
+
+
+def watch_drive_activity(registry: RunUSBRegistry):
+    with registry:
+        registry.start_user_code(Path.cwd())
+
+def watch_metadata(registry: RunUSBRegistry):
+    with registry:
+        registry.handle_metadata_file(Path.cwd() / "metadata.json")
+
+
+def main():
+    logging.basicConfig(level=logging.DEBUG)
+
+    registry = RunUSBRegistry()
+    atexit.register(registry.close)
+
+    BusHandler(registry).start()
+
+    watch_drive_activity(registry)
+    watch_metadata(registry)
+
+    # Threads are running now
+
+if __name__ == '__main__':
+    main()

runusbctl.py

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+import zmq
+from pathlib import Path
+import sys
+import time
+
+context = zmq.Context()
+
+socket = context.socket(zmq.PUB)
+socket.connect("ipc://" + str(Path.cwd() / "runusb.sock"))
+
+# time.sleep(3600)
+
+socket.send_multipart([sys.argv[1].encode(), b"foo"])

zmq_watch.py

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+import zmq
+from pathlib import Path
+
+context = zmq.Context()
+
+socket = context.socket(zmq.SUB)
+socket.setsockopt_string(zmq.SUBSCRIBE, "log")
+socket.connect("ipc://" + str(Path.cwd() / "runusb.sock"))
+
+while True:
+    print(socket.recv_multipart())