feat: Rust templates #376

jcrossley3 · 2021-06-07T23:08:32Z

Open questions:

I added a test-rust make target, but didn't add it to the existing test target yet. Does CI run that? Is cargo available there?
I did not reference a specific tagged version of the builder image in .builders.yaml and I'm not sure who makes latest available. Is that also CI?
Should I squash these to make a more cohesive commit message?

lance · 2021-06-11T20:51:33Z

Open questions:

1. I added a `test-rust` make target, but didn't add it to the existing `test` target yet. Does CI run that? Is `cargo` available there?

We use GH Actions for CI, and yes you can add cargo https://github.com/actions-rs/cargo.

2. I did not reference a specific tagged version of the builder image in `.builders.yaml` and I'm not sure who makes `latest` available. Is that also CI?

Yes when we publish a new version CI pushes to quay.io

3. Should I squash these to make a more cohesive commit message?

Your choice. We can squash when landing too.

lance

Thanks for this contribution @jcrossley3! One of the things we try to do is hide all of the plumbing from the function developer so that they are presented with only a function in their source file. Would it be possible to modify this template/buildpack combo so that it looks a little more like the Go template/buildpack?

lance · 2021-06-11T20:58:14Z

templates/rust/http/src/main.rs

+#[actix_web::main]
+async fn main() -> std::io::Result<()> {
+    elog::from_env(elog::Env::default().default_filter_or("info")).init();
+
+    let port: u16 = match std::env::var("PORT") {
+        Ok(v) => v.parse().unwrap(),
+        Err(_) => 8080,
+    };
+
+    // Create the HTTP server
+    HttpServer::new(|| {
+        App::new()
+            .wrap(actix_web::middleware::Logger::default())
+            .route("/", web::get().to(index))
+            .route("/", web::post().to(index))
+            .route(
+                "/health/{_:(readiness|liveness)}",
+                web::get().to(HttpResponse::Ok),
+            )
+    })
+    .bind(("127.0.0.1", port))?
+    .workers(1)
+    .run()
+    .await
+}


I would rather that this code live in the buildpack similar to how it's done in go.

https://github.com/boson-project/buildpacks/blob/5f204f9f69ef0c8b12ca2ef0d4298d0165f819e0/buildpacks/go/faas/main.go#L28-L39

Is it possible to change boson-project/buildpacks#95 to follow this same pattern?

That was actually my initial approach. Ultimately, I decided against it, mostly for three reasons:

There are so many different ways that App can be configured depending on the handler function signature that I couldn't justify hiding that from the user. The template is just scratching the surface of what actix provides.

The handler would be referring to actix types, so there will always be a potential version mismatch: both the runtime and the user's handler will have to depend on compatible versions of actix. I couldn't justify introducing that obstacle.

Library dependencies in rust are expressed as "crates" so I would either have to publish a crate containing these few lines of configuration code that a user will likely want to change anyway... or work up some hackery in the buildpack to make cargo think it's building a runtime crate that depends on the user's app for its handler.

In light of the latter, and the prior art of the java-based buildpacks expecting a fully-formed app from the user, I thought initially making the buildpack capable of compiling any rust app might serve the rust developer better. Heck, there are lots of alternatives to actix out there. You know as well as I do how many web frameworks we can swing a dead cat and hit.

I'm just guessing. I like magic, but only if I'm sure I'll never want to change it, and at this point, I'm not sure what I may want to change. So I figure we take a conservative approach initially and see if/how folks might use it. We can always introduce a new template later that hides the server config (App) once doing that seems obvious in hindsight.

One thing I could do is split the code into two files: main.rs and handler.rs. And we'll move the handler and its tests into the latter. Would that make things more clear?

I'm just guessing. I like magic, but only if I'm sure I'll never want to change it, and at this point, I'm not sure what I may want to change. So I figure we take a conservative approach initially and see if/how folks might use it. We can always introduce a new template later that hides the server config (App) once doing that seems obvious in hindsight.

That seems reasonable, I suppose.

One thing I could do is split the code into two files: main.rs and handler.rs. And we'll move the handler and its tests into the latter. Would that make things more clear?

Yes, I like this change. Thanks. :)

lance · 2021-06-11T21:02:35Z

templates/rust/http/src/main.rs

+use env_logger as elog;
+use log::info;
+
+async fn index(req: HttpRequest) -> HttpResponse {


I'm curious why this function is async. I apologize for my Rust ignorance. How is this async and how does that work in an HTTP request?

I'm no expert, but rust async is inspired by erlang async. In rust, you have to bring your own runtime to schedule the lightweight processes defined by that async keyword. Actix uses the tokio runtime, which ultimately gets created by that "macro attribute" on line 15: #[actix_web::main].

I'm not familiar with the actix-web internals but I expect at some point, something is invoking await on the Future returned by the index function. I know it says it's returning an HttpResponse, but because that async keyword is there, it's really returning a Future.

Were you looking for more detail than that?

Thanks that does help. I just want to make sure we don't end up with a long running async function that gets scaled to 0 before work is done. But I guess ultimately the HTTP response is not sent until the function completes. Is that a valid reading?

I think so.

jcrossley3 · 2021-06-12T14:33:53Z

We use GH Actions for CI, and yes you can add cargo https://github.com/actions-rs/cargo.

Where do I add that, exactly?

zroubalik · 2021-06-14T08:33:46Z

We use GH Actions for CI, and yes you can add cargo https://github.com/actions-rs/cargo.

Where do I add that, exactly?

Here you can find the GH Actions definitions, that are being used by CI and for PR validation.

jcrossley3 · 2021-06-14T13:16:27Z

Where do I add that, exactly?

Here you can find the GH Actions definitions, that are being used by CI and for PR validation.

Thanks. I saw that, but couldn't figure out where the other langs were being configured and then thought, "maybe rust is available, by default?" So I just updated the test target and everything worked. Yay!

jcrossley3 · 2021-06-14T20:17:01Z

Ok, I squashed my commits and I think I'm generally happy with it as an initial strawman.

zroubalik

Looking good, my Rust experience is limited though... :)

Do you think that you could add Rust Function developer guide? Something similar that has been done for other runtimes: https://github.com/boson-project/func/blob/main/docs/guides/developers_guide.md#language-guides

Thanks!

jcrossley3 · 2021-06-16T20:46:17Z

Do you think that you could add Rust Function developer guide?

@zroubalik Is there something in particular I missed in the README.md included in each template? I'm assuming the intended audience already knows rust well enough to have their environment set up and should already be pretty familiar with the cargo subcommands.

Is the guide still useful if it's mostly restating what's in the README's?

lance · 2021-06-16T20:50:26Z

@jcrossley3 it's a lot of what's in the readme, but it's also other stuff depending on the runtime/framework. Currently we try to have a language guide for each set of templates. You are probably right that this ultimately probably lands in the template itself - especially as these things start to move upstream.

jcrossley3 · 2021-06-17T15:27:23Z

Do you think that you could add Rust Function developer guide?

Done.

Each template is a fully-formed actix-web application that includes a main.rs providing the server configuration and a handler.rs showing an example function and a few simple unit tests. A README.md provides a bit more detail to get the user started. The events handler is similar to the example in the old faas-rust-runtime project.

jcrossley3 mentioned this pull request Jun 9, 2021

Post on Func and Quarkus experience drogue-iot/blog.drogue.io#18

Merged

jcrossley3 force-pushed the rust branch 2 times, most recently from f4b0d5a to 44ec063 Compare June 9, 2021 21:17

jcrossley3 marked this pull request as ready for review June 9, 2021 21:22

jcrossley3 requested review from lance, lkingland, matejvasek and zroubalik as code owners June 9, 2021 21:22

jcrossley3 force-pushed the rust branch from 44ec063 to 90ccc7d Compare June 9, 2021 21:24

lance reviewed Jun 11, 2021

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lance approved these changes Jun 14, 2021

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jcrossley3 force-pushed the rust branch from 3183410 to c8afbb9 Compare June 14, 2021 20:15

jcrossley3 force-pushed the rust branch 2 times, most recently from 4caa8c1 to b5017a5 Compare June 14, 2021 21:44

zroubalik reviewed Jun 16, 2021

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zroubalik changed the title ~~Rust templates~~ feat: Rust templates Jun 16, 2021

jcrossley3 force-pushed the rust branch from f790459 to f03c46d Compare June 16, 2021 20:36

lkingland approved these changes Jun 16, 2021

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jcrossley3 force-pushed the rust branch from 5491835 to 9e584f4 Compare June 17, 2021 17:08

jcrossley3 added 2 commits June 18, 2021 09:40

With developer guide for Rust

e3cdf4d

jcrossley3 force-pushed the rust branch from 9e584f4 to e3cdf4d Compare June 18, 2021 13:40

lance merged commit 4711638 into knative:main Jun 18, 2021

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feat: Rust templates #376

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