Determine if DeleteBucket returns NoSuchBucket

[zchenyu]

I'm trying to write some idempotent code to delete a bucket:

 _, err = s3Client.DeleteBucket(ctx, &s3.DeleteBucketInput{                                                      
    Bucket: &bucket,
})
var notFound *s3types.NoSuchBucket
if errors.As(err, &notFound) {
    fmt.Println("not found error, ok!")
} else {
    fmt.Println("other error, bad!")
}

However this doesn't work as expected. Apparently DeleteBucket returns a *smithy.Operation error instead of a types.NoSuchBucket. I verified this by printing out the error chain:

for err != nil {
  fmt.Println(reflect.ValueOf(err).Type())
  fmt.Println(err)
  err = errors.Unwrap(err)
}

which gave:

*smithy.OperationError
  operation error S3: DeleteBucket, https response error StatusCode: 404, RequestID: GDXMKMMAP9429NZ5, HostID: oxZxW3iOepOf8JukxNUejsCYNz/tfB1wgqLmTVHO+U9uYQNjrWucd6FUC/hPFXpS3qAHL7dwwzQ=, api error NoSuchBucket: The specified bucket does not exist
*s3shared.ResponseError
  https response error StatusCode: 404, RequestID: GDXMKMMAP9429NZ5, HostID: oxZxW3iOepOf8JukxNUejsCYNz/tfB1wgqLmTVHO+U9uYQNjrWucd6FUC/hPFXpS3qAHL7dwwzQ=, api error NoSuchBucket: The specified bucket does not exist
*smithy.GenericAPIError
  api error NoSuchBucket: The specified bucket does not exist

It doesn't seem like there's a way to determine if it's a NoSuchBucket error just by unwrapping. The best way I could think of is to get the smithy.GenericAPIError and check if its Code equals the string "NoSuchBucket". This doesn't seem very clean though.

Any ideas?

[zchenyu]

#1110 (comment)

Suggests to use something like

if opErr, ok := err.(*smithy.OperationError); ok {
	if httpErr, ok := opErr.Err.(*awsHttp.ResponseError); ok {
		if httpErr.HTTPStatusCode() == http.StatusNotFound {
			// 
		}
	}
}

[zchenyu]

In contrast, CreateBucket returns BucketAlreadyOwnedByYou as expected.

*smithy.OperationError
  operation error S3: CreateBucket, https response error StatusCode: 409, RequestID: KC154S6M8822CQ2T, HostID: tB0LhzK9j8glv85xOB+sfqqwWqgfXXLz6Ig+bJUtXQJXIvubsP2DlBZcOF16yJOPgSZ9D3Ll99pq3rcaOlmFlA==, BucketAlreadyOwnedByYou: 
*s3shared.ResponseError
  https response error StatusCode: 409, RequestID: KC154S6M8822CQ2T, HostID: tB0LhzK9j8glv85xOB+sfqqwWqgfXXLz6Ig+bJUtXQJXIvubsP2DlBZcOF16yJOPgSZ9D3Ll99pq3rcaOlmFlA==, BucketAlreadyOwnedByYou: 
*types.BucketAlreadyOwnedByYou
  BucketAlreadyOwnedByYou: 

[RanVaknin]

Hi @zchenyu ,

The S3 API model is the source of truth for this kind of information.
DeleteBucket has no typed errors associated with that particular operation, thus the SDK will not map the response to a typed error:

"com.amazonaws.s3#DeleteBucket": {
            "type": "operation",
            "input": {
                "target": "com.amazonaws.s3#DeleteBucketRequest"
            },
            "output": {
                "target": "smithy.api#Unit"
            },
}

CreateBucket does have 2 typed errors associated with it:

"com.amazonaws.s3#CreateBucket": {
            "type": "operation",
            "input": {
                "target": "com.amazonaws.s3#CreateBucketRequest"
            },
            "output": {
                "target": "com.amazonaws.s3#CreateBucketOutput"
            },
            "errors": [
                {
                    "target": "com.amazonaws.s3#BucketAlreadyExists"
                },
                {
                    "target": "com.amazonaws.s3#BucketAlreadyOwnedByYou"
                }
            ],
}

This really is an S3 API design choice and the SDK team can't really do anything about it since the SDK itself is code generated from that same model file.

Not entirely sure what you are trying to build, but if I understand your use case, you can use HeadBucket to check if that bucket exists and then if it does run a DeleteBucket on it.

Let me know if that helps,
Thanks,
Ran~

[zchenyu]

Thanks Ran! Is it reasonable to rely on httpErr.HTTPStatusCode() to return StatusNotFound when the bucket doesn't exist?

[RanVaknin]

I'm not entirely sure what you are trying to do.

If you mean running a delete bucket and relying on the un-modeled error to determine if that bucket exists, then I wouldn't recommend it. If this is an application not for production capacity, and you just need a code that works, then I think this would work for that use case.

Personally, I'll use this flow (pseudo code):

var res = HeadBucket({Bucket: "my-bucket"})
if res.status == 200{
  DeleteBucket({Bucket: "my-bucket"})
} 

It has more overhead since it potentially will call 2 API operations instead of 1, but it's more accurate.

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