Any interest in a PR to support WASM based clients?

[john-hern]

Hey Maintainers,

I have created a fork of tarpc, that supports WASM clients. I'm curious what the apatite is for supporting such a PR, maybe with an experimental feature flag? I have a few forked repos that have it all working end to end, see the links below. The nice thing is that the changes aren't heavy for tarpc. It really is just a few shims for the std::time/tokio::time calls and enabling a dependency feature flag (WASM support for rand crate). The only issue is I'm not sure if the time shim library is being actively maintained, I plan to file an issue with that project and see if they would accept a PR. If they aren't actively maintaining the project I can fork it and maintain it since shims aren't a lot of work and I'd like to explore this approach in a project I'm working on.

Side note: I started this a couple of weeks back, so my code is targeting tarpc 0.22, however I did test it with 0.23 (See the other branch) and it appears to work fine (IE, it compiles). I couldn't test it since my client/server have a dependency that hasn't moved to tokio 0.3 yet.

tarpc fork:
master...john-hern:wasm_support
Notes: I'll likely move the SystemTimeExt trait/impl into the wasm-timer fork/PR and implement from/into on the SystemTime type.

wasm-timer fork:
tomaka/wasm-timer@master...john-hern:tokioShim
Notes: Nothing interesting here except the reimplementation of tokio's timeout API using the shims.

server/client example.
https://github.com/john-hern/tarpc-wasm-client-tcp-server-example
Notes:
The server is using tokio + ws_stream_tungstenite to create the byte stream/sink over a websocket.
The client is a yew application, using ws_stream_wasm wasm_bindgen (spawn_local).

There are probably some caveats with edge cases. For example, the time shims wont work in a web worker. There is an issue in web-sys to address this. Once it's fixed, it should be possible to use this code in a web worker. Also, since wasms are currently single threaded there are probably some perf concerns. I'm pretty sure other things may pop up.

Thoughts?
*edit: Had the wrong link for the wasm-timer fork.

[tikue]

Hey, this is very cool! I didn't know futures worked on WASM :) I am happy to merge WASM support under a feature flag, especially since it appears to require such minimal changes. I might suggest providing a tarpc::time module facade so that the other modules don't have to have #[cfg(wasm)] scattered about.

[john-hern]

Awesome. I'll reach out to the wasm-timer team and see if I can elicit a response. I already updated the branches to add the façade (Good suggestion), and moved over the SystemTime conversation to an into implementation in that crate. I'll circle back in a week or two once I get a better feeling about their ability to support the project long term. I'll update this thread with a link to the issue once I create it for tracking.

[bbarker]

Any updates on this? I'd love to be able to have RPC clients in the browser!

[tikue]

@john-hern closing due to inactivity but feel free to reopen if you pick this back up!

[davidatsurge]

FYI, the following patch (to 75b15fe) allows tarpc to compile on wasm32-unknown-unknown now.

diff --git a/Cargo.toml b/Cargo.toml
index c7557d0..3e8109d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,7 +2,7 @@
 resolver = "2"
 
 members = [
-    "example-service",
+    # "example-service",
     "tarpc",
     "plugins",
 ]
diff --git a/tarpc/Cargo.toml b/tarpc/Cargo.toml
index b2f037b..34255b3 100644
--- a/tarpc/Cargo.toml
+++ b/tarpc/Cargo.toml
@@ -61,6 +61,8 @@ tracing = { version = "0.1", default-features = false, features = [
 tracing-opentelemetry = { version = "0.17.2", default-features = false }
 opentelemetry = { version = "0.17.0", default-features = false }
 
+[target.wasm32-unknown-unknown.dependencies]
+getrandom = { version = "0.2.7" , features = [ "js" ] }
 
 [dev-dependencies]
 assert_matches = "1.4"

Note that we're not compiling example-service/ at all since I didn't look into making that wasm-compatible. Also, I haven't actually tried to see if it not only compiles, but it works (since this is Rust, I assume that to be the case).

I have put aside tarpc for now, but I thought I'd share this.