As per the long outstanding GH issue this starts our rigorous journey
into an attempt at a type-safe, cross-actor SC, IPC protocol Bo
boop -> https://github.com/goodboy/tractor/issues/36
The idea is to "formally" define our SC "shuttle (dialog) protocol" by
specifying a new `.msg.types.Msg` subtype-set which can fully
encapsulate all IPC msg schemas needed in order to accomplish
cross-process SC!
------ - ------
The msg set deviated a little in terms of (type) names from the existing
`dict`-msgs currently used in the runtime impl but, I think the msg name
changes are much better in terms of explicitly representing the internal
semantics of the actor runtime machinery subsystems and IPC-msg-dialog
required for SC enforced RPC. In cursory, the new formal msgs-spec
includes the following msg-subtypes of a new top-level `Msg` boxing type
(that holds the base field schema for all msgs):
- `Start` to request RPC task scheduling by passing a `FuncSpec`
payload (implemented currently with a `{'cmd': ... }` dict msg)
- `StartAck` to allow the RPC task callee-side to report a `IpcCtxSpec`
payload immediately back to the caller (currently done naively via
a `{'functype': ... }` initial response msg)
- `Started` to deliver the first value from `Context.started()`
(instead of existing `{'started': ... }`)
- `Yield` to shuttle `MsgStream.send()`-ed values (currently
`{'yield': ... }`s)
- `Stop` to terminate a `Context.open_stream()` session/block (currently
a `{'stop': True }`)
- `Return` to deliver the final value from the `Actor.start_remote_task()`
remote task (instead of `{'return': ... }`)
- `Error` to box `RemoteActorError` exceptions via a `.pld: ErrorData`
payload, also planned to replace/extend the current
`RemoteActorError.msgdata` mechanism internal to `pack/unpack_error()`
The new `tractor.msg.types` includes all these msg defs as well an API
for rendering a "payload msg specification" using a `payload_type_spec:
Union[Type]` that can be passed to
`msgspec.msgpack.Decoder(type=payload_type_spec)`. This ensures that
(per msg relevant) `Msg.pld: PayloadT` data is type-parameterized using
`msgspec`'s new `Generic[PayloadT]` field support and thus enables
providing for an API where IPC `Context` dialogs can strictly define the
allowed payload-msg-set by a type union!
Iow, this is the foundation for supporting `Channel`/`Context`/`MsgStream`
IPC primitives which are type checked/safe as desired in GH issue:
- https://github.com/goodboy/tractor/issues/365
Misc notes on current impl(s) status:
------ - ------
- add a `.msg.types.mk_msg_spec()` which uses the new `msgspec` support
for `class MyStruct[Struct, Generic[T]]` parameterize-able fields and
delivers our boxing SC-msg-(sub)set with the desired `payload_types`
applied to `.pld`:
- https://jcristharif.com/msgspec/supported-types.html#generic-types
- as a note this impl seems to need to use `type.new_class()` dynamic
subtype generation, though i don't really get *why* still.. but
without that the `msgspec.msgpack.Decoder` doesn't seem to reject
`.pld` limited `Msg` subtypes as demonstrated in the new test.
- around this ^ add a `.msg._codec.limit_msg_spec()` cm which exposes
this payload type limiting API such that it can be applied per task
via a `MsgCodec` in app code.
- the orig approach in https://github.com/goodboy/tractor/pull/311 was
the idea of making payload fields `.pld: Raw` wherein we could have
per-field/sub-msg decoders dynamically loaded depending on the
particular application-layer schema in use. I don't want to lose the
idea of this since I think it might be useful for an idea I have about
capability-based-fields(-sharing, maybe using field-subset
encryption?), and as such i've kept the (ostensibly) working impls in
TODO-comments in `.msg._codec` wherein maybe we can add
a `MsgCodec._payload_decs: dict` table for this later on.
|_ also left in the `.msg.types.enc/decmsg()` impls but renamed as
`enc/dec_payload()` (but reworked to not rely on the lifo codec
stack tables; now removed) such that we can prolly move them to
`MsgCodec` methods in the future.
- add an unused `._codec.mk_tagged_union_dec()` helper which was
originally factored out the #311 proto-code but didn't end up working
as desired with the new parameterized generic fields approach (now
in `msg.types.mk_msg_spec()`)
Testing/deps work:
------ - ------
- new `test_limit_msgspec()` which ensures all the `.types` content is
correct but without using the wrapping APIs in `._codec`; i.e. using
a in-line `Decoder` instead of a `MsgCodec`.
- pin us to `msgspec>=0.18.5` which has the needed generic-types support
(which took me way too long yester to figure out when implementing all
this XD)!
Fitting in line with the issues outstanding:
- #36: (msg)spec-ing out our SCIPP (structured-con-inter-proc-prot).
(https://github.com/goodboy/tractor/issues/36)
- #196: adding strictly typed IPC msg dialog schemas, more or less
better described as "dialog/transaction scoped message specs"
using `msgspec`'s tagged unions and custom codecs.
(https://github.com/goodboy/tractor/issues/196)
- #365: using modern static type-annots to drive capability based
messaging and RPC.
(statically https://github.com/goodboy/tractor/issues/365)
This is a first draft of a new API for dynamically overriding IPC msg
codecs for a given interchange lib from any task in the runtime. Right
now we obviously only support `msgspec` but ideally this API holds
general enough to be used for other backends eventually (like
`capnproto`, and apache arrow).
Impl is in a new `tractor.msg._codec` with:
- a new `MsgCodec` type for encapsing `msgspec.msgpack.Encoder/Decoder`
pairs and configuring any custom enc/dec_hooks or typed decoding.
- factory `mk_codec()` for creating new codecs ad-hoc from a task.
- `contextvars` support for a new `trio.Task` scoped
`_ctxvar_MsgCodec: ContextVar[MsgCodec]` named 'msgspec_codec'.
- `apply_codec()` for temporarily modifying the above per task
as needed around `.open_context()` / `.open_stream()` operation.
A new test (suite) in `test_caps_msging.py`:
- verify a parent and its child can enable the same custom codec (in
this case to transmit `NamespacePath`s) with tons of pedantic ctx-vars
checks.
- ToDo: still need to implement #36 msg types in order to be able to get
decodes working (as in `MsgStream.receive()` will deliver an already
created `NamespacePath` obj) since currently all msgs come packed in `dict`-msg
wrapper packets..
-> use the proto from PR #35 to get nested `msgspec.Raw` processing up
and running Bo
Tyler Goodlet