58e9211d71
The `api.API` provides a `setup-stdio` method, that is meant to be used by clients to replace their stdio with the supplied fds from the server. Provide a canonical `api.setup_stdio` method that will do exactly that.
147 lines
4.4 KiB
Python
147 lines
4.4 KiB
Python
import abc
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import asyncio
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import io
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import json
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import os
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import sys
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import tempfile
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import threading
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from .util import jsoncomm
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__all__ = [
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"API"
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]
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class BaseAPI(abc.ABC):
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"""Base class for all API providers
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This base class provides the basic scaffolding for setting
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up API endpoints, normally to be used for bi-directional
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communication from and to the sandbox. It is to be used as
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a context manger. The communication channel will only be
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established on entering the context and will be shut down
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when the context is left.
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The `_dispatch` method needs to be implemented by child
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classes, and is called for incoming messages.
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Optionally, the `_cleanup` method can be implemented, to
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clean up resources after the context is left and the
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communication channel shut down.
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"""
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def __init__(self, socket_address):
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self.socket_address = socket_address
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self.barrier = threading.Barrier(2)
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self.event_loop = None
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self.thread = None
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@abc.abstractmethod
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def _dispatch(self, server):
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"""Called for incoming messages on the socket"""
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def _cleanup(self):
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"""Called after the event loop is shut down"""
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def _run_event_loop(self):
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with jsoncomm.Socket.new_server(self.socket_address) as server:
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self.barrier.wait()
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self.event_loop.add_reader(server, self._dispatch, server)
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asyncio.set_event_loop(self.event_loop)
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self.event_loop.run_forever()
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self.event_loop.remove_reader(server)
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def __enter__(self):
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# We are not re-entrant, so complain if re-entered.
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assert self.event_loop is None
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self.event_loop = asyncio.new_event_loop()
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self.thread = threading.Thread(target=self._run_event_loop)
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self.barrier.reset()
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self.thread.start()
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self.barrier.wait()
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return self
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def __exit__(self, *args):
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self.event_loop.call_soon_threadsafe(self.event_loop.stop)
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self.thread.join()
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self.event_loop.close()
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# Give deriving classes a chance to clean themselves up
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self._cleanup()
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self.thread = None
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self.event_loop = None
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class API(BaseAPI):
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"""The main OSBuild API"""
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def __init__(self, socket_address, args, monitor):
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super().__init__(socket_address)
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self.input = args
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self._output_data = io.StringIO()
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self._output_pipe = None
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self.monitor = monitor
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@property
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def output(self):
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return self._output_data.getvalue()
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def _prepare_input(self):
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with tempfile.TemporaryFile() as fd:
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fd.write(json.dumps(self.input).encode('utf-8'))
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# re-open the file to get a read-only file descriptor
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return open(f"/proc/self/fd/{fd.fileno()}", "r")
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def _prepare_output(self):
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r, w = os.pipe()
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self._output_pipe = r
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self._output_data.truncate(0)
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self._output_data.seek(0)
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self.event_loop.add_reader(r, self._output_ready)
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return os.fdopen(w)
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def _output_ready(self):
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raw = os.read(self._output_pipe, 4096)
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data = raw.decode("utf-8")
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self._output_data.write(data)
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self.monitor.log(data)
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def _setup_stdio(self, server, addr):
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with self._prepare_input() as stdin, \
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self._prepare_output() as stdout:
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msg = {}
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fds = []
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fds.append(stdin.fileno())
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msg['stdin'] = 0
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fds.append(stdout.fileno())
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msg['stdout'] = 1
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fds.append(stdout.fileno())
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msg['stderr'] = 2
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server.send(msg, fds=fds, destination=addr)
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def _dispatch(self, server):
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msg, _, addr = server.recv()
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if msg["method"] == 'setup-stdio':
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self._setup_stdio(server, addr)
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def _cleanup(self):
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if self._output_pipe:
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os.close(self._output_pipe)
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self._output_pipe = None
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def setup_stdio(path="/run/osbuild/api/osbuild"):
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"""Replace standard i/o with the ones provided by the API"""
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with jsoncomm.Socket.new_client(path) as client:
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req = {"method": "setup-stdio"}
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client.send(req)
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msg, fds, _ = client.recv()
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for sio in ["stdin", "stdout", "stderr"]:
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target = getattr(sys, sio)
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source = fds[msg[sio]]
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os.dup2(source, target.fileno())
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fds.close()
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