cloudformatious

A CloudFormation library offering richly typed higher-level APIs to perform long-running operations and await their termination or observe their progress.

use futures_util::StreamExt;

use cloudformatious::{ApplyStackInput, DeleteStackInput, TemplateSource};

#[tokio::main]
async fn main() -> Result<(), Box<dyn std::error::Error>> {
    let config = aws_config::load_from_env().await;
    let client = cloudformatious::Client::new(&config);

    let input = ApplyStackInput::new("my-stack", TemplateSource::inline("{}"));
    let mut stack = client.apply_stack(input);

    let mut events = stack.events();
    while let Some(event) = events.next().await {
        eprintln!("{:#?}", event);
    };

    let output = stack.await?;
    eprintln!("Stack applied");
    println!("{:#?}", output);

    let input = DeleteStackInput::new(output.stack_id);
    client.delete_stack(input).await?;

    println!("Stack deleted");

    Ok(())
}

Motivation

CloudFormation's API is relatively low-level. This makes it possible to implement fairly advanced workflows involving things like manual review of changes before applying, but it makes the common case of an idempotent 'apply this template' deployment a bit awkward. There are other tools that can mitigate this, such as the aws cloudformation deploy high-level command, but their output is very limited so they only really do half of the work. Furthermore, the tools that I'm aware of are primarily invoked from the shell, meaning they cannot be integrated natively into programs that wish to orchestrate CloudFormation stacks.

Features

The CloudFormatious extension trait has the following methods:

• apply_stack which implements an idempotent 'update or create stack' operation.
• delete_stack which implements an idempotent delete stack operation.

In both cases, the API is a bit more ergonomic than aws_sdk_cloudformation and the API is richer. In particular:

• The return value of both methods implements Future, which can be awaited to wait for the overall operation to end.
• The return value of both methods has an events() method, which can be used to get a Stream of stack events that occur during the operation.
• Both methods return rich Err values if the stack settles in a failing state.
• Both methods return rich Err values if the stack operation succeeds, but some resource(s) had errors (these "warnings" can be ignored, but it may mean leaving extraneous infrastructure in your environment).
• apply_stack returns a rich Ok value with 'cleaner' types than the generated aws_sdk_cloudformation types (fewer redundant Options, enums for mutually exclusive states, etc.).

Contributing

Feedback and PRs are welcome. However, if you'd like to add any non-trivial functionality it may be worth opening an issue to discuss it first.

License

MIT