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tractor/tractor/msg/_codec.py

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# tractor: structured concurrent "actors".
# Copyright 2018-eternity Tyler Goodlet.
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <https://www.gnu.org/licenses/>.
'''
IPC msg interchange codec management.
Supported backend libs:
- `msgspec.msgpack`
ToDo: backends we prolly should offer:
- see project/lib list throughout GH issue discussion comments:
https://github.com/goodboy/tractor/issues/196
- `capnproto`: https://capnproto.org/rpc.html
- https://capnproto.org/language.html#language-reference
'''
from __future__ import annotations
from contextvars import (
ContextVar,
Token,
)
from contextlib import (
contextmanager as cm,
)
from typing import (
Any,
Callable,
Type,
Union,
)
from types import ModuleType
import msgspec
from msgspec import msgpack
from tractor.msg.pretty_struct import Struct
from tractor.msg.types import (
mk_msg_spec,
Msg,
)
# TODO: overall IPC msg-spec features (i.e. in this mod)!
#
# -[ ] API changes towards being interchange lib agnostic!
# -[ ] capnproto has pre-compiled schema for eg..
# * https://capnproto.org/language.html
# * http://capnproto.github.io/pycapnp/quickstart.html
# * https://github.com/capnproto/pycapnp/blob/master/examples/addressbook.capnp
#
# -[ ] struct aware messaging coders as per:
# -[x] https://github.com/goodboy/tractor/issues/36
# -[ ] https://github.com/goodboy/tractor/issues/196
# -[ ] https://github.com/goodboy/tractor/issues/365
#
class MsgCodec(Struct):
'''
A IPC msg interchange format lib's encoder + decoder pair.
'''
# post-configure-cached when prop-accessed (see `mk_codec()`
# OR can be passed directly as,
# `MsgCodec(_enc=<Encoder>, _dec=<Decoder>)`
_enc: msgpack.Encoder|None = None
_dec: msgpack.Decoder|None = None
# struct type unions
# https://jcristharif.com/msgspec/structs.html#tagged-unions
@property
def ipc_pld_spec(self) -> Union[Type[Struct]]:
return self._dec.type
lib: ModuleType = msgspec
# ad-hoc type extensions
# https://jcristharif.com/msgspec/extending.html#mapping-to-from-native-types
enc_hook: Callable[[Any], Any]|None = None # coder
dec_hook: Callable[[type, Any], Any]|None = None # decoder
# TODO: a sub-decoder system as well?
# payload_msg_specs: Union[Type[Struct]] = Any
# see related comments in `.msg.types`
# _payload_decs: (
# dict[
# str,
# msgpack.Decoder,
# ]
# |None
# ) = None
# OR
# ) = {
# # pre-seed decoders for std-py-type-set for use when
# # `Msg.pld == None|Any`.
# None: msgpack.Decoder(Any),
# Any: msgpack.Decoder(Any),
# }
# TODO: use `functools.cached_property` for these ?
# https://docs.python.org/3/library/functools.html#functools.cached_property
@property
def enc(self) -> msgpack.Encoder:
return self._enc
def encode(
self,
py_obj: Any,
) -> bytes:
'''
Encode input python objects to `msgpack` bytes for transfer
on a tranport protocol connection.
'''
return self._enc.encode(py_obj)
@property
def dec(self) -> msgpack.Decoder:
return self._dec
def decode(
self,
msg: bytes,
) -> Any:
'''
Decode received `msgpack` bytes into a local python object
with special `msgspec.Struct` (or other type) handling
determined by the
'''
return self._dec.decode(msg)
# TODO: do we still want to try and support the sub-decoder with
# `.Raw` technique in the case that the `Generic` approach gives
# future grief?
#
# -[ ] <NEW-ISSUE-FOR-ThIS-HERE>
#
#def mk_pld_subdec(
# self,
# payload_types: Union[Type[Struct]],
#) -> msgpack.Decoder:
# # TODO: sub-decoder suppor for `.pld: Raw`?
# # => see similar notes inside `.msg.types`..
# #
# # not sure we'll end up needing this though it might have
# # unforeseen advantages in terms of enabling encrypted
# # appliciation layer (only) payloads?
# #
# # register sub-payload decoders to load `.pld: Raw`
# # decoded `Msg`-packets using a dynamic lookup (table)
# # instead of a pre-defined msg-spec via `Generic`
# # parameterization.
# #
# (
# tags,
# payload_dec,
# ) = mk_tagged_union_dec(
# tagged_structs=list(payload_types.__args__),
# )
# # register sub-decoders by tag
# subdecs: dict[str, msgpack.Decoder]|None = self._payload_decs
# for name in tags:
# subdecs.setdefault(
# name,
# payload_dec,
# )
# return payload_dec
# sub-decoders for retreiving embedded
# payload data and decoding to a sender
# side defined (struct) type.
# def dec_payload(
# codec: MsgCodec,
# msg: Msg,
# ) -> Any|Struct:
# msg: Msg = codec.dec.decode(msg)
# payload_tag: str = msg.header.payload_tag
# payload_dec: msgpack.Decoder = codec._payload_decs[payload_tag]
# return payload_dec.decode(msg.pld)
# def enc_payload(
# codec: MsgCodec,
# payload: Any,
# cid: str,
# ) -> bytes:
# # tag_field: str|None = None
# plbytes = codec.enc.encode(payload)
# if b'msg_type' in plbytes:
# assert isinstance(payload, Struct)
# # tag_field: str = type(payload).__name__
# payload = msgspec.Raw(plbytes)
# msg = Msg(
# cid=cid,
# pld=payload,
# # Header(
# # payload_tag=tag_field,
# # # dialog_id,
# # ),
# )
# return codec.enc.encode(msg)
#def mk_tagged_union_dec(
# tagged_structs: list[Struct],
#) -> tuple[
# list[str],
# msgpack.Decoder,
#]:
# '''
# Create a `msgpack.Decoder` for an input `list[msgspec.Struct]`
# and return a `list[str]` of each struct's `tag_field: str` value
# which can be used to "map to" the initialized dec.
# '''
# # See "tagged unions" docs:
# # https://jcristharif.com/msgspec/structs.html#tagged-unions
# # "The quickest way to enable tagged unions is to set tag=True when
# # defining every struct type in the union. In this case tag_field
# # defaults to "type", and tag defaults to the struct class name
# # (e.g. "Get")."
# first: Struct = tagged_structs[0]
# types_union: Union[Type[Struct]] = Union[
# first
# ]|Any
# tags: list[str] = [first.__name__]
# for struct in tagged_structs[1:]:
# types_union |= struct
# tags.append(
# getattr(
# struct,
# struct.__struct_config__.tag_field,
# struct.__name__,
# )
# )
# dec = msgpack.Decoder(types_union)
# return (
# tags,
# dec,
# )
def mk_codec(
ipc_msg_spec: Union[Type[Struct]]|Any|None = None,
#
# ^TODO^: in the long run, do we want to allow using a diff IPC `Msg`-set?
# it would break the runtime, but maybe say if you wanted
# to add some kinda field-specific or wholesale `.pld` ecryption?
# struct type unions set for `Decoder`
# https://jcristharif.com/msgspec/structs.html#tagged-unions
ipc_pld_spec: Union[Type[Struct]]|Any|None = None,
# TODO: offering a per-msg(-field) type-spec such that
# the fields can be dynamically NOT decoded and left as `Raw`
# values which are later loaded by a sub-decoder specified
# by `tag_field: str` value key?
# payload_msg_specs: dict[
# str, # tag_field value as sub-decoder key
# Union[Type[Struct]] # `Msg.pld` type spec
# ]|None = None,
libname: str = 'msgspec',
# proxy as `Struct(**kwargs)`
# ------ - ------
dec_hook: Callable|None = None,
enc_hook: Callable|None = None,
# ------ - ------
**kwargs,
#
# Encoder:
# write_buffer_size=write_buffer_size,
#
# Decoder:
# ext_hook: ext_hook_sig
) -> MsgCodec:
'''
Convenience factory for creating codecs eventually meant
to be interchange lib agnostic (i.e. once we support more then just
`msgspec` ;).
'''
if (
ipc_msg_spec is not None
and ipc_pld_spec
):
raise RuntimeError(
f'If a payload spec is provided,\n'
"the builtin SC-shuttle-protocol's msg set\n"
f'(i.e. `{Msg}`) MUST be used!\n\n'
f'However both values were passed as => mk_codec(\n'
f' ipc_msg_spec={ipc_msg_spec}`\n'
f' ipc_pld_spec={ipc_pld_spec}`\n)\n'
)
elif (
ipc_pld_spec
and
# XXX required for now (or maybe forever?) until
# we can dream up a way to allow parameterizing and/or
# custom overrides to the `Msg`-spec protocol itself?
ipc_msg_spec is None
):
# (manually) generate a msg-payload-spec for all relevant
# god-boxing-msg subtypes, parameterizing the `Msg.pld: PayloadT`
# for the decoder such that all sub-type msgs in our SCIPP
# will automatically decode to a type-"limited" payload (`Struct`)
# object (set).
(
ipc_msg_spec,
msg_types,
) = mk_msg_spec(
payload_type_union=ipc_pld_spec,
)
assert len(ipc_msg_spec.__args__) == len(msg_types)
assert ipc_msg_spec
dec = msgpack.Decoder(
type=ipc_msg_spec, # like `Msg[Any]`
)
else:
ipc_msg_spec = ipc_msg_spec or Any
enc = msgpack.Encoder(
enc_hook=enc_hook,
)
dec = msgpack.Decoder(
type=ipc_msg_spec, # like `Msg[Any]`
dec_hook=dec_hook,
)
codec = MsgCodec(
_enc=enc,
_dec=dec,
# payload_msg_specs=payload_msg_specs,
# **kwargs,
)
# sanity on expected backend support
assert codec.lib.__name__ == libname
return codec
# instance of the default `msgspec.msgpack` codec settings, i.e.
# no custom structs, hooks or other special types.
_def_msgspec_codec: MsgCodec = mk_codec(ipc_msg_spec=Any)
# NOTE: provides for per-`trio.Task` specificity of the
# IPC msging codec used by the transport layer when doing
# `Channel.send()/.recv()` of wire data.
_ctxvar_MsgCodec: ContextVar[MsgCodec] = ContextVar(
'msgspec_codec',
# TODO: move this to our new `Msg`-spec!
default=_def_msgspec_codec,
)
@cm
def apply_codec(
codec: MsgCodec,
) -> MsgCodec:
'''
Dynamically apply a `MsgCodec` to the current task's
runtime context such that all IPC msgs are processed
with it for that task.
'''
token: Token = _ctxvar_MsgCodec.set(codec)
try:
yield _ctxvar_MsgCodec.get()
finally:
_ctxvar_MsgCodec.reset(token)
def current_msgspec_codec() -> MsgCodec:
'''
Return the current `trio.Task.context`'s value
for `msgspec_codec` used by `Channel.send/.recv()`
for wire serialization.
'''
return _ctxvar_MsgCodec.get()
@cm
def limit_msg_spec(
payload_types: Union[Type[Struct]],
# TODO: don't need this approach right?
# -> related to the `MsgCodec._payload_decs` stuff above..
# tagged_structs: list[Struct]|None = None,
**codec_kwargs,
):
'''
Apply a `MsgCodec` that will natively decode the SC-msg set's
`Msg.pld: Union[Type[Struct]]` payload fields using
tagged-unions of `msgspec.Struct`s from the `payload_types`
for all IPC contexts in use by the current `trio.Task`.
'''
msgspec_codec: MsgCodec = mk_codec(
payload_types=payload_types,
**codec_kwargs,
)
with apply_codec(msgspec_codec):
yield msgspec_codec
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