wstd-aws: wstd support for the AWS Rust SDK

This crate provides support for using the AWS Rust SDK for the wasm32-wasip2 target using the wstd crate.

In many wasi settings, its necessary or desirable to use the wasi-http interface to make http requests. Wasi-http interfaces provide an http implementation, including the sockets layer and TLS, outside of the user's component. wstd provides user-friendly async Rust interfaces to all of the standardized wasi interfaces, including wasi-http.

The AWS Rust SDK, by default, depends on tokio, hyper, and either rustls or s2n_tls, and makes http requests over sockets (which can be provided as wasi-sockets). Those dependencies may not work correctly under wasm32-wasip2, and if they do, they will not use the wasi-http interfaces. To avoid using http over sockets, make sure to set the default-features = false setting when depending on any aws-* crates in your project.

To configure wstd's wasi-http client for the AWS Rust SDK, provide wstd_aws::sleep_impl() and wstd_aws::http_client() to your aws_config::ConfigLoader:

    let config = aws_config::defaults(BehaviorVersion::latest())
        .sleep_impl(wstd_aws::sleep_impl())
        .http_client(wstd_aws::http_client())
        ...;

Example

An example s3 client is provided as a wasi cli command. It accepts command line arguments with the subcommand list to list a bucket's contents, and get <key> to get an object from a bucket and write it to the filesystem.

This example must be compiled in release mode - in debug mode, the aws sdk's generated code will overflow the maximum permitted wasm locals in a single function.

Compile it with:

cargo build -p wstd-aws --target wasm32-wasip2 --release --examples

When running this example, you will need AWS credentials provided in environment variables.

Run it with:

wasmtime run -Shttp \
    --env AWS_ACCESS_KEY_ID \
    --env AWS_SECRET_ACCESS_KEY \
    --env AWS_SESSION_TOKEN \
    --dir .::. \
    target/wasm32-wasip2/release/examples/s3.wasm

or alternatively run it with:

cargo run --target wasm32-wasip2 -p wstd-aws --example s3

which uses the wasmtime cli, as above, via configiration found in this workspace's .cargo/config.

By default, this script accesses the wstd-example-bucket in us-west-2. To change the bucket or region, use the --bucket and --region cli flags before the subcommand.