Amazon SageMaker: Invoke endpoint with file as multipart/form-data

The first problem is that you're using 'http' for your CURL request. Virtually all AWS services strictly use 'https' as their protocol, SageMaker included. https://docs.aws.amazon.com/general/latest/gr/rande.html. I'm going to assume this was a typo though.

You can check the verbose output of the AWS CLI by passing the '--debug' argument to your call. I re-ran a similar experiment with my favorite duck.jpg image:

aws --debug sagemaker-runtime invoke-endpoint --endpoint-name MyEndpoint --body image=@/duck.jpg --content-type multipart/form-data  >(cat)

Looking at the output, I see:

2018-08-10 08:42:20,870 - MainThread - botocore.endpoint - DEBUG - Making request for OperationModel(name=InvokeEndpoint) (verify_ssl=True) with params: {'body': 'image=@/duck.jpg', 'url': u'https://sagemaker.us-west-2.amazonaws.com/endpoints/MyEndpoint/invocations', 'headers': {u'Content-Type': 'multipart/form-data', 'User-Agent': 'aws-cli/1.15.14 Python/2.7.10 Darwin/16.7.0 botocore/1.10.14'}, 'context': {'auth_type': None, 'client_region': 'us-west-2', 'has_streaming_input': True, 'client_config': <botocore.config.Config object at 0x109a58ed0>}, 'query_string': {}, 'url_path': u'/endpoints/MyEndpoint/invocations', 'method': u'POST'}

It looks like the AWS CLI is using the string literal '@/duck.jpg', not the file contents.

Trying again with curl and the "--verbose" flag:

curl --verbose -X POST -F "image=@/duck.jpg" https://sagemaker.us-west-2.amazonaws.com/endpoints/MyEndpoint/invocations

I see the following:

Content-Length: 63097

Much better. The '@' operator is a CURL specific feature. The AWS CLI does have a way to pass files though:

--body fileb:///duck.jpg

There is also a 'file' for non-binary files such as JSON. Unfortunately you cannot have the prefix. That is, you cannot say:

 --body image=fileb:///duck.jpg

You can prepend the string 'image=' to your file with a command such as the following. (You'll probably need to be more clever if your images are really big; this is really inefficient.)

 echo -e "image=$(cat /duck.jpg)" > duck_with_prefix

Your final command would then be:

 aws sagemaker-runtime invoke-endpoint --endpoint-name MyEndpoint --body fileb:///duck_with_prefix --content-type multipart/form-data  >(cat)

Another note: Using raw curl with AWS services is extremely difficult due to the AWS Auth signing requirements - https://docs.aws.amazon.com/AmazonS3/latest/API/sig-v4-authenticating-requests.html

It can be done, but you'll likely be more productive by using the AWS CLI or a pre-existing tool such as Postman - https://docs.aws.amazon.com/apigateway/latest/developerguide/how-to-use-postman-to-call-api.html