Enable binary responses in the http-templates

[alexellis]

Signed-off-by: Alex Ellis (OpenFaaS Ltd) alexellis2@gmail.com

Description

Enable binary responses in the http-templates

Motivation and Context

This was not possible previously, and resulted in a byte array being converted to a string and creating an invalid file.

To opt in, set the content type appropriately as: application/octet-stream.

How Has This Been Tested?

Before / after - one created a lot of serialised bytes and the after I got an image.

from PIL import Image
import io

# Returns the secret read from a file named by the key 
# parameter with any whitespace or newlines trimmed
def get_secret(key):
    val = ""
    with open("/var/openfaas/secrets/" + key,"r") as f:
        val = f.read().strip()
    return val

def handle(event, context):
    secret = get_secret("bw-api-key")
    if event.headers.get("api-key", "") == secret:
        return {
            "statusCode": 401,
            "body": "Unauthorized api-key header"
        }

    buf = io.BytesIO()
    with Image.open(io.BytesIO(event.body)) as im:
        im_grayscale = im.convert("L")
        try:
            im_grayscale.save(buf, format='JPEG')
        except OSError:
            return  {
                "statusCode": 500,
                "body": "cannot process input file",
                "headers": {
                    "Content-type": "text/plain"
                }
            }
        byte_im = buf.getvalue()

        # Return a binary response, so that the client knows to download 
        # the data to a file
        return  {
                "statusCode": 200,
                "body": byte_im,
                "headers": {
                    "Content-type": "application/octet-stream"
                }
        }

[alexellis]

Also tested subsequently when setting no headers.

[alexellis]

Thank you for looking. That is a good point,I felt like I'd missed something obvious.