CopyObjectAsync method throws AmazonS3Exception when source object doesn't exist.

[olizarevichroman]

Describe the bug

When trying to copy not existing object s3 client throws an exception with error code NoSuchKey and CopyObjectResponse is null.

Expected Behavior

I would say we should provide error in CopyObjectRequest. At least we should set an appropriate http status code.

Also it's not clear how a library consumer should determine that it's an issue with source key, cause the only way I see here is to check that ErrorCode == "NoSuchKey" what seems weird.

Current Behavior

Amazon.S3.AmazonS3Exception: The specified key does not exist.
 ---> Amazon.Runtime.Internal.HttpErrorResponseException: Exception of type 'Amazon.Runtime.Internal.HttpErrorResponseException' was thrown.
   at Amazon.Runtime.HttpWebRequestMessage.GetResponseAsync(CancellationToken cancellationToken)
   at Amazon.Runtime.Internal.HttpHandler`1.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.RedirectHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.Unmarshaller.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.S3.Internal.AmazonS3ResponseHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.ErrorHandler.InvokeAsync[T](IExecutionContext executionContext)
   --- End of inner exception stack trace ---
   at Amazon.Runtime.Internal.HttpErrorResponseExceptionHandler.HandleExceptionStream(IRequestContext requestContext, IWebResponseData httpErrorResponse, HttpErrorResponseException exception, Stream responseStream)
   at Amazon.Runtime.Internal.HttpErrorResponseExceptionHandler.HandleExceptionAsync(IExecutionContext executionContext, HttpErrorResponseException exception)
   at Amazon.Runtime.Internal.ExceptionHandler`1.HandleAsync(IExecutionContext executionContext, Exception exception)
   at Amazon.Runtime.Internal.ErrorHandler.ProcessExceptionAsync(IExecutionContext executionContext, Exception exception)
   at Amazon.Runtime.Internal.ErrorHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.CallbackHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.Signer.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.EndpointDiscoveryHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.EndpointDiscoveryHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.CredentialsRetriever.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.RetryHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.RetryHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.CallbackHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.CallbackHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.S3.Internal.AmazonS3ExceptionHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.ErrorCallbackHandler.InvokeAsync[T](IExecutionContext executionContext)
   at Amazon.Runtime.Internal.MetricsHandler.InvokeAsync[T](IExecutionContext executionContext)

Reproduction Steps

Execute CopyObjectAsync on s3 client passing not existing SourceKey.

Possible Solution

Don't throw an exception but pass error context into CopyObjectResponse object

Additional Information/Context

No response

AWS .NET SDK and/or Package version used

AWSSDK.S3 3.7.107.5

Targeted .NET Platform

.NET 7

Operating System and version

OSX Ventura 13.4.1

[ashishdhingra]

@olizarevichroman Good morning. Thanks for reporting the concern. The behavior to throw an exception is as per design. The behavior is also controlled by service models which may define what exceptions a particular service operation may throw (for example NoSuchKey). This behavior is uniform across all AWS SDK(s) and is unlikely to change.

For your use case, you may develop a middleware with POCO object for each service operation that could have a shape with members like StatusCode and <ServiceOperation>Response object, where your middleware would catch specific exceptions and returns POCO object with specified status code to the caller.

I'm converting this to Q&A discussion since the behavior is unlikely to change and is as per design.

Thanks,
Ashish

[olizarevichroman]

Hi, thanks for quick response.

In case it is an expected behavior then it might be useful to have all these error codes presented for consumer.

If I understand correctly aws-sdk-go has an object holding all these error strings - https://github.com/aws/aws-sdk-go/blob/main/service/s3/errors.go. Having such an object will help matching errors without hardcoding aws specific error codes. Cause ErrorCode == "NoSuchKey" doesn't look as reliable way to handle errors. Once aws-sdk decide to change error code consumer should be aware of it or catch this error from tests.

Also having specific exception like NoSuchKeyException looks good, but it requires lots of changes.

[ashishdhingra]

@olizarevichroman For .NET SDK (and Java SDK as well per best of my knowledge), we are not maintaining list of error codes. The error code could be determined by examining the InnerException property of AmazonS3Exception object. Each service API operation could return a different set of exceptions, refer Error Responses.

[github-actions[bot]]

Hello! Reopening this discussion to make it searchable.