Fetch bucket location and include in HeadBucket response

[Copilot]

HeadBucket now returns the x-amz-bucket-region header per AWS S3 specification with the actual bucket location fetched from libuplink.

Changes

• miniogw/gateway.go: Added GetBucketLocation method that uses bucket.GetBucketLocation from libuplink to fetch the actual bucket location
• api/api.go: Added BucketLocationGetter interface for type assertion to access the gateway layer's GetBucketLocation method
• api/buckethandlers.go: Updated HeadBucketHandler to fetch actual bucket location and set x-amz-bucket-region header only when location is available. Optimized to use a single call to GetBucketLocation when available instead of two separate calls.

// HeadBucketHandler now makes a single optimized call
// TODO: Add GetBucketLocation to the object layer interface in storj/minio
// instead of using type assertion. This would allow us to make a single call
// instead of two separate calls (GetBucketInfo + GetBucketLocation).
if locationGetter, ok := api.objectAPI.(BucketLocationGetter); ok {
    location, err := locationGetter.GetBucketLocation(ctx, bucketName)
    if err != nil {
        writeErrorResponseHeadersOnly(w, cmd.ToAPIError(ctx, err))
        return
    }
    if location != "" {
        w.Header().Set(xhttp.AmzBucketRegion, location)
    }
} else {
    // Fallback to GetBucketInfo if GetBucketLocation is not available
    if _, err := api.objectAPI.GetBucketInfo(ctx, bucketName); err != nil {
        writeErrorResponseHeadersOnly(w, cmd.ToAPIError(ctx, err))
        return
    }
}

Implementation Details

The implementation is optimized to use a single libuplink call when possible. When the object layer implements BucketLocationGetter, it makes only one call to GetBucketLocation (which validates bucket exists AND returns location). It falls back to GetBucketInfo only when GetBucketLocation is not available. The handler uses type assertion to check if the object layer supports location fetching and only sets the header when a location is successfully retrieved. No default fallback value is used.

A TODO comment has been added to track future work: adding GetBucketLocation to the object layer interface in storj/minio would eliminate the need for type assertion and further streamline the implementation.

Original prompt

there's an ongoing effort to migrate bucket and object handlers from our MinIO fork. while this is happening, let's extend the HeadBucket handler to include the bucket's region in its response. you may need to extract the BucketInfo struct from the MinIO fork and place it in this codebase directly.

references:

• https://docs.aws.amazon.com/AmazonS3/latest/API/API_HeadBucket.html
• https://docs.aws.amazon.com/AmazonS3/latest/API/API_GetBucketLocation.html (no longer a best practice)

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[amwolff]

no, this won't cut it. we need to modify the implementation of the bucket info-gathering action to fetch information about the bucket along with its region and pass it down here. find out if there's a libuplink method that will allow us to do it in one libuplink call instead of two (bucket info + bucket location).

[Copilot]

no, this won't cut it. we need to modify the implementation of the bucket info-gathering action to fetch information about the bucket along with its region and pass it down here. find out if there's a...

Done in d743731. The implementation now:

1. Added GetBucketLocation method to gatewayLayer that calls bucket.GetBucketLocation from libuplink
2. Created GetBucketInfoWithLocation helper in the API layer that fetches both bucket info and location in separate calls (StatBucket + GetBucketLocation)
3. Updated HeadBucketHandler to use the actual bucket location from libuplink
4. Falls back to "us-east-1" if location cannot be retrieved

There's no single libuplink method that returns both bucket info and location, so the implementation uses two separate calls as you suggested to investigate.

[amwolff]

@copilot CI is still failing on this (https://build.dev.storj.tools/job/gateway-st/job/PR-107/6/display/redirect)

[Copilot]

@copilot CI is still failing on this (https://build.dev.storj.tools/job/gateway-st/job/PR-107/6/display/redirect)

I've verified the code locally - it builds successfully, all tests pass, and linting checks (go vet, check-imports, check-copyright, check-mod-tidy) all pass. Without access to the full CI logs, I cannot determine the specific failure. Could you share the error message from the CI failure so I can address it?