Stream: wasi

Topic: wasmtime serve + wasi-http example

Andrew Brown (Jan 29 2024 at 20:14):

I was trying to use wasmtime serve today but ran into dependency problems: what is the set of versions and build options that will allow that to work?

I am currently (1) retrieving WIT dependencies with wit-dep, (2) building a simplistic (and raw) HTTP server by exporting ""wasi:http/incoming-handler" with wit-bindgen, (3) putting the pieces together using wasm-tools component new (including the preview1 adapter) and (4) attempting to run this with wasmtime serve. I invariably get errors like "import wasi:cli/environment@0.2.0-rc-2024-01-16 has the wrong type`."

I suspect that what is going on is that the preview1 adapter is bringing in unnecessary dependencies (unnecessary to my test program, I mean). I'm not sure why they would have the wrong type, seeing as I'm using Wasmtime on main.

Andrew Brown (Jan 29 2024 at 20:15):

I have looked at @Brooks Townsend's guide (here) for how to do this with the wash CLI but I wanted to understand all the pieces in raw form. Is there no working example for wasmtime serve somewhere?

Alex Crichton (Jan 29 2024 at 20:15):

This is likely related to the adapter you're using. If you're using *.reactor.wasm you'll need to pass -S common to enable access to APIs not in the default proxy world. Otherwise you'll need to use *.proxy.wasm to not need -S common

Andrew Brown (Jan 29 2024 at 20:17):

I only see wasi_snapshot_preview1.wasm when I build the adapter with cargo build -p wasi-preview1-component-adapter --target wasm32-unknown-unknown --release

Alex Crichton (Jan 29 2024 at 20:18):

ah if building from source you'll need to frob cargo features

Andrew Brown (Jan 29 2024 at 20:18):

ok, let's try that

Alex Crichton (Jan 29 2024 at 20:18):

I think you'll need --no-default-features --features proxy

Andrew Brown (Jan 29 2024 at 20:23):

Ok, that works:

# In Wasmtime:
$ cargo build -p wasi-preview1-component-adapter --target wasm32-unknown-unknown --release --no-default-features --features proxy
$ ll -h target/wasm32-unknown-unknown/release/wasi_snapshot_preview1.wasm
-rwxr-xr-x. 2 abrown abrown 28K Jan 29 12:19 target/wasm32-unknown-unknown/release/wasi_snapshot_preview1.wasm

# In example project:
$ wasm-tools component new ./target/wasm32-wasi/debug/test_wasi_http.wasm \
        -o target/wasm32-wasi/debug/test-component.wasm \
        --adapt ../wasmtime/target/wasm32-unknown-unknown/release/wasi_snapshot_preview1.wasm
$ wasm-tools component wit target/wasm32-wasi/debug/test-component.wasm
package root:component;

world root {
  import wasi:io/error@0.2.0;
  import wasi:io/streams@0.2.0;
  import wasi:http/types@0.2.0;
  import wasi:cli/stdout@0.2.0;
  import wasi:cli/stderr@0.2.0;
  import wasi:cli/stdin@0.2.0;

  export wasi:http/incoming-handler@0.2.0;
}

That seems like the right number and kind of imports; way fewer than I was seeing earlier. And just a note: I don't see any special *.proxy.wasm or *.reactor.wasm in the adapter.

Alex Crichton (Jan 29 2024 at 20:25):

When you say "in the adapter", can you clarify? I should clarify when I say *.proxy.wasm I mean from Wasmtime's releases page where we manually rename a few things

Andrew Brown (Jan 29 2024 at 20:25):

And wasmtime serve now works:

$ wasmtime serve target/wasm32-wasi/debug/test-component.wasm
Serving HTTP on http://0.0.0.0:8080/

Alex Crichton (Jan 29 2024 at 20:25):

Note that -Scommon isn't necessary with the proxy version of the adapter

Andrew Brown (Jan 29 2024 at 20:26):

[edited to remove that part]

Andrew Brown (Jan 29 2024 at 20:26):

Alex Crichton said:

When you say "in the adapter", can you clarify? I should clarify when I say *.proxy.wasm I mean from Wasmtime's releases page where we manually rename a few things

I mean that when I build the adapter from source, I do not see any special file name suffixes. I didn't know to look in the release artifacts?

Alex Crichton (Jan 29 2024 at 20:28):

Oh you're correct that there's no suffix when building from source

Andrew Brown (Jan 29 2024 at 20:28):

I looked around in the Wasmtime repository for a CLI test of some kind that does all of this: did I miss it or is that just not there yet?

Alex Crichton (Jan 29 2024 at 20:28):

And by artifacts I mean at the top level of this page, not within tarballs themselves

Alex Crichton (Jan 29 2024 at 20:29):

This is the closest equivalent to in-repo tests

Last updated: Nov 22 2024 at 16:03 UTC