Timo Stark (Jan 15 2024 at 19:33): Timo Stark (Jan 15 2024 at 19:33):Hello! I am trying to move away from wasm-tools component new and use cargo component build instead. I have successfully installed cargo-component and the build command finished BUT trying to use wasmtime serve tells me the wasm binary is not a component. After using wasm-tools with the preview1_reactor everything works just fine .
My example is based on the Spin SDK: https://github.com/fermyon/spin/blob/v2.1/examples/http-rust/src/lib.rs
Sorry for the obvious stupid question but I just would like to understand what can I do to get the most out of the cargo-component
Peter Huene (Jan 15 2024 at 22:55):Hi @Timo Stark. I am unfamiliar with the Spin SDK and what it normally is expecting to produce.
If cargo component build is not producing a component (something that's easily verified with wasm-tools print <path/to/wasm> to see if it starts with component), then it's likely that there were no component type information section emitted into the core module output from the Rust toolchain. That can happen if you're not explicitly generating bindings with wit_bindgen::generate or cargo_component_bindings::generate and also when not linking in any crate dependencies that similarly didn't include any bindings.
If you'd like to file an issue on the cargo-component repository with repro steps, I am happy to take a look and see what the problem is.
Timo Stark (Jan 15 2024 at 22:59):Thanks Peter! Thats helpful information. I think what you just described is the core issue. I have updated the examples in my Github and guess I will try to find out on how to mod the Cargo.toml to make thinks work with cargo component. https://github.com/tippexs/unit-power-spin/tree/main/application
I really don't think this is an issue on your end but would appreciate if you could have a quick look into the gh repo just shared.
Peter Huene (Jan 15 2024 at 23:06):Briefly looking at Spin's macro source, it does appear to be invoking wit_bindgen::generate! under the covers, so I would expect the component type information section to be present in the resulting core module; I'll try to look into this tomorrow as it's a holiday in the States today.
Timo Stark (Jan 15 2024 at 23:07):No hurry @Peter Huene .Really appreciate it! I have a working solution using wasm-tools so this is not super critical. Thanks a lot for your help
Peter Huene (Jan 15 2024 at 23:07):Oh I think I spotted the issue
Peter Huene (Jan 15 2024 at 23:08):add a [package.metadata.component] section to your Cargo.toml and see if cargo component build now produces a component
Timo Stark (Jan 15 2024 at 23:08):Will do. One second
Peter Huene (Jan 15 2024 at 23:09):cargo-component is expecting that section (it's what cargo component new outputs) to inform the tool that the package should be treated as a component vs. any other package type (e.g. a Rust package that's really meant to be a wasm core module as output)
Timo Stark (Jan 15 2024 at 23:11):Ahhh I see. Just created a new one to have a reference. Let me copy this into the other Cargo.toml
Timo Stark (Jan 15 2024 at 23:14):Okay great! This generates a component! Thanks. But is there a way to define what reactor it should use? I guess I saw something in the docs. Let me check! Don't want to keep you on this any longer on your free day!
Timo Stark (Jan 15 2024 at 23:14):Thanks a lot for your help! This was perfect!
Peter Huene (Jan 15 2024 at 23:15):You can specify adapter = "path/to/adapter.wasm" in the package.medata.component table
Peter Huene (Jan 15 2024 at 23:16):which will override the built-in adapter
Timo Stark (Jan 15 2024 at 23:18):Yes ... Just found it in the docs! It woks! Excellent support! Thanks Peter!
Timo Stark (Jan 15 2024 at 23:19):As a reference for others. The Cargo.toml using Fermyon Spin SDK AND cargo component looks like
[package]
name = "application"
version = "0.1.0"
edition = "2021"
[package.metadata.component]
package = "component:application"
adapter = "./wasi_snapshot_preview1.reactor.wasm"
[lib]
crate-type = [ "cdylib" ]
[dependencies]
anyhow = "1"
http = "0.2.9"
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"
spin-sdk = "2.1.0"
Timo Stark has marked this topic as resolved.
Last updated: Nov 25 2024 at 19:03 UTC