20 releases (10 breaking)
new 0.10.1 | Sep 13, 2024 |
---|---|
0.9.0 | Aug 27, 2024 |
0.4.0 | Jul 27, 2024 |
0.0.0 | Jan 23, 2024 |
#818 in WebAssembly
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SLoC
wRPC
Component-native transport-agnostic RPC protocol and framework based on WebAssembly Interface Types (WIT)
A Bytecode Alliance hosted project
About
wRPC facilitates execution of arbitrary functionality defined in WIT over network or other means of communication.
Main use cases for wRPC are:
- out-of-tree WebAssembly runtime plugins
- distributed WebAssembly component communication
Even though wRPC is designed for Wasm components first and foremost, it is fully usable outside of WebAssembly context and can serve as a general-purpose RPC framework.
wRPC uses component model value definiton encoding on the wire.
wRPC supports both dynamic (based on e.g. runtime WebAssembly component type introspection) and static use cases.
For static use cases, wRPC provides WIT binding generators for:
- Rust
- Go
wRPC fully supports the unreleased native WIT stream
and future
data types along with all currently released WIT functionality.
Quickstart
wRPC usage examples for different programming languages can be found at examples.
There are 2 different kinds of examples:
- Native wRPC applications, tied to a particular wRPC transport (currently, NATS only)
- Generic Wasm components, that need to run in a Wasm runtime. Those can be executed, for example, using
wrpc-wasmtime-nats
, to polyfill imports at runtime and serve exports using wRPC.
hello
example
In this example we will serve and invoke a simple hello
application using:
- examples/rust/hello-component-client
- examples/rust/hello-component-server
- examples/rust/hello-nats-client
- examples/rust/hello-nats-server
Requirements
nats-server
>= 2.10.20 ordocker
>= 24.0.6 (or any other OCI runtime)rust
>= 1.80.1
How-To
In the steps below, wasm32-wasip1
target will be used, because it is currently available in stable Rust and also conveniently configured in rust-toolchain.toml
in the root of this repository.
wasm32-wasip2
can be used instead, if desired.
-
Build Wasm
hello
client:cargo build --release -p hello-component-client --target wasm32-wasip1
Output is in target/wasm32-wasip1/release/hello-component-client.wasm
-
Build Wasm
hello
server:cargo build --release -p hello-component-server --target wasm32-wasip1
Output is in target/wasm32-wasip1/release/hello_component_server.wasm
NB: Rust uses
_
separators in the filename, because a component is built as a reactor-style library -
Build the wRPC Wasm runtime:
cargo build --release --bin wrpc-wasmtime-nats
Output is in target/release/wrpc-wasmtime-nats or target/release/wrpc-wasmtime-nats.exe on Windows
-
Run NATS (more thorough documentation available here):
- using standalone binary:
nats-server
- using Docker:
docker run --rm -it --name nats-server -p 4222:4222 nats:2.10.20-alpine3.20
-
Serve Wasm
hello
server via NATS:./target/release/wrpc-wasmtime-nats serve rust rust ./target/wasm32-wasip1/release/hello_component_server.wasm
- Sample output:
INFO async_nats: event: connected
INFO wrpc_wasmtime_nats_cli: serving instance function name="hello"
-
Call Wasm
hello
server using a Wasmhello
client via NATS:./target/release/wrpc-wasmtime-nats run rust ./target/wasm32-wasip1/release/hello-component-client.wasm
- Sample output in the client:
INFO async_nats: event: connected
hello from Rust
- Sample output in the server:
INFO wrpc_wasmtime_nats_cli: serving instance function invocation headers=None
INFO wrpc_wasmtime_nats_cli: successfully served instance function invocation
-
Call the Wasm
hello
server using a native wRPChello
client:cargo run -p hello-nats-client rust
-
Serve native wRPC
hello
server:cargo run -p hello-nats-server native
-
Call both the native wRPC
hello
server and Wasmhello
server using native wRPChello
client:cargo run -p hello-nats-client rust native
-
Call native wRPC
hello
server using Wasmhello
client via NATS:./target/release/wrpc-wasmtime-nats run native ./target/wasm32-wasip1/release/hello-component-client.wasm
Design
Transport
wRPC transport is the core abstraction on top of which all the other functionality is built.
A transport represents a multiplexed bidirectional communication channel, over which wRPC invocations are transmitted.
wRPC operates under assumption that transport communication channels can be "indexed" by a sequence of unsigned 32-bit integers, which represent a reflective structural path.
Invocation
As part of every wRPC invocation at least 2 independent, directional byte streams will be established by the chosen transport:
- parameters (client -> server)
- results (server -> client)
wRPC transport implementations MAY (and are encouraged to) provide two more directional communication channels:
- client error (client -> server)
- server error (server -> client)
Error channels are the only channels that are typed, in particular, values sent on these channels are strings.
If async
values are being transmitted as parameters or results of an invocation, wRPC MAY send those values on an indexed path asynchronously.
Consider the invocation of WIT function foo
from instance wrpc-example:doc/example@0.1.0
:
package wrpc-example:doc@0.1.0;
interface example {
record rec {
a: stream<u8>,
b: u32,
}
foo: func(v: rec) -> stream<u8>;
}
- Since
foo
parameter0
is arecord
, which contains anasync
type (stream
) as the first field, wRPC will communicate to the transport that apart from the "root" parameter channel, it may need to receive results at index path0
(first return value). - wRPC will encode the parameters as a single-element tuple in a non-blocking fashion. If full contents of
rec.a
are not available at the time of encoding, the stream will be encoded asoption::none
. - (concurrently, if in
2.
stream was not fully available) wRPC will transfer the contents of thestream<u8>
on parameter byte stream at index0->0
(first field of the record, which is the first parameter) as they become available. - wRPC will attempt to decode
stream<u8>
from the "root" result byte stream. - (if
4.
decoded anoption::none
for thestream
value) wRPC will attempt to decodestream<u8>
from result byte stream at index0
Note, that the handler of foo
(server) MAY:
- receive
rec.b
value beforerec.a
is sent or even available - send a result back to the invoker of
foo
(client) before it has receivedrec.a
Repository structure
This repository contains (for all supported languages):
- core libraries and abstractions
- binding generators
- WebAssembly runtime integrations
- wRPC transport implementations
wit-bindgen-wrpc
aims to closely match UX of wit-bindgen
and therefore includes a subtree merge of the project, which is occasionally merged into this tree.
- wRPC binding generators among other tests, are tested using the
wit-bindgen
test suite wit-bindgen
documentation is reused where applicable
Contributing
👋 Welcome, new contributors!
Whether you're a seasoned developer or just getting started, your contributions are valuable to us. Don't hesitate to jump in, explore the project, and make an impact. To start contributing, please check out our Contribution Guidelines.
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