# mypy: allow-untyped-defs
import base64
import json
import os
import threading
import queue
import uuid
from multiprocessing.managers import BaseManager, BaseProxy
# We also depend on some undocumented parts of multiprocessing.managers which
# don't have any type annotations.
from multiprocessing.managers import AcquirerProxy, DictProxy, public_methods # type: ignore
from typing import Dict
from .utils import isomorphic_encode
class StashManager(BaseManager):
shared_data: Dict[str, object] = {}
lock = threading.Lock()
def _get_shared():
return StashManager.shared_data
def _get_lock():
return StashManager.lock
StashManager.register("get_dict",
callable=_get_shared,
proxytype=DictProxy)
StashManager.register('Lock',
callable=_get_lock,
proxytype=AcquirerProxy)
# We have to create an explicit class here because the built-in
# AutoProxy has a bug with nested managers, and the MakeProxy
# method doesn't work with spawn-based multiprocessing, since the
# generated class can't be pickled for use in child processes.
class QueueProxy(BaseProxy):
_exposed_ = public_methods(queue.Queue)
for method in QueueProxy._exposed_:
def impl_fn(method):
def _impl(self, *args, **kwargs):
return self._callmethod(method, args, kwargs)
_impl.__name__ = method
return _impl
setattr(QueueProxy, method, impl_fn(method)) # type: ignore
StashManager.register("Queue",
callable=queue.Queue,
proxytype=QueueProxy)
class StashServer:
def __init__(self, address=None, authkey=None, mp_context=None):
self.address = address
self.authkey = authkey
self.manager = None
self.mp_context = mp_context
def __enter__(self):
self.manager, self.address, self.authkey = start_server(self.address,
self.authkey,
self.mp_context)
store_env_config(self.address, self.authkey)
def __exit__(self, *args, **kwargs):
if self.manager is not None:
self.manager.shutdown()
def load_env_config():
address, authkey = json.loads(os.environ["WPT_STASH_CONFIG"])
if isinstance(address, list):
address = tuple(address)
else:
address = str(address)
authkey = base64.b64decode(authkey)
return address, authkey
def store_env_config(address, authkey):
authkey = base64.b64encode(authkey)
os.environ["WPT_STASH_CONFIG"] = json.dumps((address, authkey.decode("ascii")))
def start_server(address=None, authkey=None, mp_context=None):
if isinstance(authkey, str):
authkey = authkey.encode("ascii")
kwargs = {}
if mp_context is not None:
kwargs["ctx"] = mp_context
manager = StashManager(address, authkey, **kwargs)
manager.start()
address = manager._address
if isinstance(address, bytes):
address = address.decode("ascii")
return (manager, address, manager._authkey)
class LockWrapper:
def __init__(self, lock):
self.lock = lock
def acquire(self):
self.lock.acquire()
def release(self):
self.lock.release()
def __enter__(self):
self.acquire()
def __exit__(self, *args, **kwargs):
self.release()
#TODO: Consider expiring values after some fixed time for long-running
#servers
class Stash:
"""Key-value store for persisting data across HTTP/S and WS/S requests.
This data store is specifically designed for persisting data across server
requests. The synchronization is achieved by using the BaseManager from
the multiprocessing module so different processes can acccess the same data.
Stash can be used interchangeably between HTTP, HTTPS, WS and WSS servers.
A thing to note about WS/S servers is that they require additional steps in
the handlers for accessing the same underlying shared data in the Stash.
This can usually be achieved by using load_env_config(). When using Stash
interchangeably between HTTP/S and WS/S request, the path part of the key
should be expliclitly specified if accessing the same key/value subset.
The store has several unusual properties. Keys are of the form (path,
uuid), where path is, by default, the path in the HTTP request and
uuid is a unique id. In addition, the store is write-once, read-once,
i.e. the value associated with a particular key cannot be changed once
written and the read operation (called "take") is destructive. Taken together,
these properties make it difficult for data to accidentally leak
between different resources or different requests for the same
resource.
"""
_proxy = None
lock = None
manager = None
_initializing = threading.Lock()
def __init__(self, default_path, address=None, authkey=None):
self.default_path = default_path
self._get_proxy(address, authkey)
self.data = Stash._proxy
def _get_proxy(self, address=None, authkey=None):
if address is None and authkey is None:
Stash._proxy = {}
Stash.lock = threading.Lock()
# Initializing the proxy involves connecting to the remote process and
# retrieving two proxied objects. This process is not inherently
# atomic, so a lock must be used to make it so. Atomicity ensures that
# only one thread attempts to initialize the connection and that any
# threads running in parallel correctly wait for initialization to be
# fully complete.
with Stash._initializing:
if Stash.lock:
return
Stash.manager = StashManager(address, authkey)
Stash.manager.connect()
Stash._proxy = self.manager.get_dict()
Stash.lock = LockWrapper(self.manager.Lock())
def get_queue(self):
return self.manager.Queue()
def _wrap_key(self, key, path):
if path is None:
path = self.default_path
# This key format is required to support using the path. Since the data
# passed into the stash can be a DictProxy which wouldn't detect
# changes when writing to a subdict.
if isinstance(key, bytes):
# UUIDs are within the ASCII charset.
key = key.decode('ascii')
try:
my_uuid = uuid.UUID(key).bytes
except ValueError as e:
raise ValueError(f"""Invalid UUID "{key}" used as stash key""") from e
return (isomorphic_encode(path), my_uuid)
def put(self, key, value, path=None):
"""Place a value in the shared stash.
:param key: A UUID to use as the data's key.
:param value: The data to store. This can be any python object.
:param path: The path that has access to read the data (by default
the current request path)"""
if value is None:
raise ValueError("SharedStash value may not be set to None")
internal_key = self._wrap_key(key, path)
if internal_key in self.data:
raise StashError("Tried to overwrite existing shared stash value "
"for key %s (old value was %s, new value is %s)" %
(internal_key, self.data[internal_key], value))
else:
self.data[internal_key] = value
def take(self, key, path=None):
"""Remove a value from the shared stash and return it.
:param key: A UUID to use as the data's key.
:param path: The path that has access to read the data (by default
the current request path)"""
internal_key = self._wrap_key(key, path)
value = self.data.get(internal_key, None)
if value is not None:
try:
self.data.pop(internal_key)
except KeyError:
# Silently continue when pop error occurs.
pass
return value
class StashError(Exception):
pass
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