CODEWITHSUNDEEP
amazon-web-servicescsvpdfamazon-s3api-gateway
Ethan Brouwer
Ethan Brouwer

Reputation: 1005

How to facilitate downloading both CSV and PDF from API Gateway connected to S3

In the app I'm working on, we have a process whereby a user can download a CSV or PDF version of their data. The generation works great, but I'm trying to get it to download the file and am running into all sorts of problems. We're using API Gateway for all the requests, and the generation happens inside a Lambda on a POST request. The GET endpoint takes in a file_name parameter and then constructs the path in S3 and then makes the request directly there. The problem I'm having is when I'm trying to transform the response. I get a 500 error and when I look at the logs, it says Execution failed due to configuration error: Unable to transform response. So, clearly that's where I've spent most of my time. I've tried at least 50 different iterations of templates and combinations with little success. The closest I've gotten is the following code, where the CSV downloads fine, but the PDF is not a valid PDF anymore:

CSV:

#set($contentDisposition = "attachment;filename=${method.request.querystring.file_name}")
$input.body
#set($context.responseOverride.header.Content-Disposition = $contentDisposition)

PDF:

#set($contentDisposition = "attachment;filename=${method.request.querystring.file_name}")
$util.base64Encode($input.body)
#set($context.responseOverride.header.Content-Disposition = $contentDisposition)

where contentHandling = CONVERT_TO_TEXT. My binaryMediaTypes just has application/pdf and that's it. My goal is to get this working without having to offload the problem into a Lambda so we don't have that overhead at the download step. Any ideas how to do this right?

Just as another comment, I've tried CONVERT_TO_BINARY and just leaving it as Passthrough. I've tried it with text/csv as another binary media type and I've tried different combinations of encoding and decoding base64 and stuff. I know the data is coming back right from S3, but the transformation is where it's breaking. I am happy to post more logs if need be. Also, I'm pretty sure this makes sense on StackOverflow, but if it would fit in another StackExchange site better, please let me know.

Resources I've looked at:

EDIT: One Idea I've had is to do CONVERT_TO_BINARY and somehow base64 encode the CSVs in the transformation, but I can't figure out how to do it right. I keep feeling like I'm misunderstanding the order of things, specifically when the "CONVERT" part happens. If that makes any sense.

EDIT 2: So, I got rid of the $util.base64Encode in the PDF one and now I have a PDF that's empty. The actual file in S3 definitely has things in it, but for some reason CONVERT_TO_TEXT is not handling it right or I'm still not understading how this all works.

Upvotes: 2

Views: 1865

Answers (1)

DaafVader
DaafVader

Reputation: 1754

Had similar issues. One major thing is the Accept header. I was testing in chrome which sends Accept header as text/html,application/xhtml.... api-gateway ignores everything except the first one(text/html). It will then convert any response from S3 to base64 to try and conform to text/html.

At last after trying everything else I tried via Postman which defaults the Accept header to */*. Also set your content handling on the Integration response to Passthrough. And everything was working!

One other thing is to pass the Content-Type and Content-Length headers through(Add them in method response first and then in Integration response):

Content-Length integration.response.header.Content-Length
Content-Type integration.response.header.Content-Type

Upvotes: 2

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