Sagemaker Data Capture does not write files

Question

I want to enable data capture for a specific endpoint (so far, only via the console). The endpoint works fine and also logs & returns the desired results. However, no files are written to the specified S3 location.

### Endpoint Configuration ###

The endpoint is based on a training job with a scikit learn classifier. It has only one variant which is a `ml.m4.xlarge` instance type. Data Capture is enabled with a sampling percentage of 100%. As data capture storage locations I tried `s3://` as well as `s3:///`. With the "Capture content type" I tried leaving everything blank, setting `text/csv` in "CSV/Text" and `application/json` in "JSON".

### Endpoint Invokation ###

The endpoint is invoked in a Lambda function with a client. Here's the call:
```
sagemaker_body_source = {
            "segments": segments,
            "language": language
        }
payload = json.dumps(sagemaker_body_source).encode()
response = self.client.invoke_endpoint(EndpointName=endpoint_name,
                                       Body=payload,
                                       ContentType='application/json',
                                       Accept='application/json')
result = json.loads(response['Body'].read().decode())
return result["predictions"]
```
Internally, the endpoint uses a Flask API with an `/invocation` path that returns the result.

### Logs ###

The endpoint itself works fine and the Flask API is logging input and output:
```
INFO:api:body: {'segments': [], 'language': 'de'}
```

```
INFO:api:output: {'predictions': [{'text': 'some text', 'label': 'some_label'}, ....]}
```

Accepted Answer

So the issue seemed to be related to the IAM role. The default role (`ModelEndpoint-Role`) does not have access to write S3 files. It worked via the SDK since it uses another role in the sagemaker studio. I did not receive any error message about this.

Answer

I had the same issue, and it was also related to IAM roles, but with a slight variation. When creating my Sagemaker domain I created a role with the suggested `AmazonSageMakerFullAccess` role. This role does have permission to write to S3 buckets, but only to those fulfilling any of the the patterns:
```
"arn:aws:s3:::*SageMaker*",
"arn:aws:s3:::*Sagemaker*",
"arn:aws:s3:::*sagemaker*",
"arn:aws:s3:::*aws-glue*"
```
As my bucket did not contain either of these patterns, it wasn't allowed to write to it. After renaming my bucket to contain "sagemaker" it worked.

Sagemaker Data Capture does not write files

Endpoint Configuration

Endpoint Invokation

Logs

Relevant content