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rfc0009_example_consolidation.md

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RFC: Examples Consolidation

Status: Implemented

Currently, the AWS Rust SDK's examples are duplicated across awslabs/aws-sdk-rust, smithy-lang/smithy-rs, and awsdocs/aws-doc-sdk-examples. The smithy-rs repository was formerly the source of truth for examples, with the examples being copied over to aws-sdk-rust as part of the release process, and examples were manually copied over to aws-doc-sdk-examples so that they could be included in the developer guide.

Now that the SDK is more stable with less frequent breaking changes, the aws-doc-sdk-examples repository can become the source of truth so long as the examples are tested against smithy-rs and continue to be copied into aws-sdk-rust.

Requirements

  1. Examples are authored and maintained in aws-doc-sdk-examples
  2. Examples are no longer present in smithy-rs
  3. CI in smithy-rs checks out examples from aws-doc-sdk-examples and builds them against the generated SDK. Success for this CI job is optional for merging since there can be a time lag between identifying that examples are broken and fixing them.
  4. Examples must be copied into aws-sdk-rust so that the examples for a specific version of the SDK can be easily referenced.
  5. Examples must be verified in aws-sdk-rust prior to merging into the main branch.

Example CI in smithy-rs

A CI job will be added to smithy-rs that:

  1. Depends on the CI job that generates the full AWS SDK
  2. Checks out the aws-doc-sdk-examples repository
  3. Modifies example Cargo.toml files to point to the newly generated AWS SDK crates
  4. Runs cargo check on each example

This job will not be required to pass for branch protection, but will let us know that examples need to be updated before the next release.

Auto-sync to aws-sdk-rust from smithy-rs changes

The auto-sync job that copies generated code from smithy-rs into the aws-sdk-rust/next branch will be updated to check out the aws-doc-sdk-examples repository and copy the examples into aws-sdk-rust. The example Cargo.toml files will also be updated to point to the local crate paths as part of this process.

The aws-sdk-rust CI already requires examples to compile, so merging next into main, the step required to perform a release, will be blocked until the examples are fixed.

In the event the examples don't work on the next branch, developers and example writers will need to be able to point the examples in aws-doc-sdk-examples to the generated SDK in next so that they can verify their fixes. This can be done by hand, or a tool can be written to automate it if a significant number of examples need to be fixed.

Process Risks

There are a couple of risks with this approach:

  1. Risk: Examples are broken and an urgent fix needs to be released.

    Possible mitigations:

    1. Revert the change that broke the examples and then add the urgent fix
    2. Create a patch branch in aws-sdk-rust, apply the fix to that based off an older version of smithy-rs with the fix applied, and merge that into main.

  2. Risk: A larger project requires changes to examples prior to GA, but multiple releases need to occur before the project completion.

    Possible mitigations:

    1. If the required changes compile against the older SDK, then just make the changes to the examples.
    2. Feature gate any incremental new functionality in smithy-rs, and work on example changes on a branch in aws-doc-sdk-examples. When wrapping up the project, remove the feature gating and merge the examples into the main branch.

Alternatives

aws-sdk-rust as the source of truth

Alternatively, the examples could reside in aws-sdk-rust, be referenced from smithy-rs CI, and get copied into aws-doc-sdk-examples for inclusion in the user guide.

Pros:

  • Prior to GA, fixing examples after making breaking changes to the SDK would be easier. Otherwise, Cargo.toml files have to be temporarily modified to point to the aws-sdk-rust/next branch in order to make fixes.
  • If a customer discovers examples via the aws-sdk-rust repository rather than via the SDK user guide, then it would be more obvious how to make changes to examples. At time of writing, the examples in the user guide link to the aws-doc-sdk-examples repository, so if the examples are discovered that way, then updating them should already be clear.

Cons:

  • Tooling would need to be built to sync examples from aws-sdk-rust into aws-doc-sdk-examples so that they could be incorporated into the user guide.
  • Creates a circular dependency between the aws-sdk-rust and smithy-rs repositories. CI in smithy-rs needs to exercise examples, which would be in aws-sdk-rust, and aws-sdk-rust has its code generated by smithy-rs. This is workable, but may lead to problems later on.

The tooling to auto-sync from aws-sdk-rust into aws-doc-sdk-examples will likely cost more than tooling to temporarily update Cargo.toml files to make example fixes (if that tooling is even necessary).

Changes Checklist

  • Add example CI job to smithy-rs
  • Diff examples in smithy-rs and aws-doc-sdk-examples and move desired differences into aws-doc-sdk-examples
  • Apply example fix PRs from aws-sdk-rust into aws-doc-sdk-examples
  • Update smithy-rs CI to copy examples from aws-doc-sdk-examples rather than from smithy-rs
  • Delete examples from smithy-rs