S3 conditional GETs should return an easier to manage error

[jmklix]

Transfered from awslabs/aws-sdk-rust: awslabs/aws-sdk-rust#534

Describe the feature

If one wants to perform a conditional GET from S3, it seems the current pattern is:

    let client = Client::new(&shared_config);
    let resp1 = client
        .get_object()
        .bucket(bucket.to_string())
        .key(from.to_string())
        .set_if_modified_since(last_modified)
        .send()
        .await;

    if let Err(e) = resp1 {
        match e {
            SdkError::ServiceError {
                err: _,
                raw: ref ra,
            } => {
                if ra.http().status() == 304 {
                    tracing::info!("not modified");
                    return Ok(last_modified);
                }
                return Err(e.into());
            }
            _ => return Err(e.into()),
        }
    } else {
        let mut resp = resp1?;
        let tmp = to.as_ref().to_path_buf().with_extension("tmp");
        if let Some(parent) = to.as_ref().parent() {
            tokio::fs::create_dir_all(parent).await?;
        }
        {
            let mut file = File::create(tmp.as_path()).await?;
            while let Some(bytes) = resp.body.next().await {
                let bytes = bytes?;
                file.write_all(&bytes).await?;
            }
            file.flush().await?;
        }
        tokio::fs::rename(tmp, to).await?;
        info!("Downloaded");
        Ok(resp.last_modified().cloned())
    }

Use Case

More intuitively handle the conditional S3 GET. Maybe there's already some way to handle this that I missed.

Proposed Solution

It seems to me that perhaps ServiceError should provide an API to quickly determine if it's a NotModified error, also perhaps adding NotModified variant to GetObjectErrorKind since right now this falls under Unhandled which requires to go deeper into the raw Response.

Other Information

No response

Acknowledgements

• I may be able to implement this feature request
• This feature might incur a breaking change

A note for the community

Community Note

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[jmklix]

P76487895

[jmklix]

I reached out to the S3 team and shared your use case to gather more insights on your behalf. Since this issue isn’t directly actionable by the SDK team, and this repository is dedicated to SDK-related issues, I'll go ahead and close this ticket. If you have access to AWS support through the Developer Console, please consider creating a support ticket and referencing the ticket ID I shared above to receive updates directly from the service team. Otherwise, you can keep an eye on our release notes for news on when this is resolved.

[github-actions]

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