preview.md

Preview in Docflow

Let's see how the preview feature of DocFlow works. 🚀

• 🎯 Endpoint: GET /v2/preview/:document
• ⚙️ Params: {document: <docuent_id_or_name>}
• 🔐 Authorization: Bearer <token>

➰ cURL:

curl --location 'localhost:8000/v2/preview/:document' \
--header 'Authorization: Bearer <token>'

Here in Preview we use two important models, fastapi.response's FileResponse amd tempfile's NamedTemporaryFile.

FileResponse is used to return files.

NamedTemporaryFile is a function in Python's tempfile module that creates a temporary file with a unique name in the system's default location for temporary files. This function returns a file-like object that can be used in a similar way to other file objects.

Here is the brief explanation on how it works:

• When we call NameTemporaryFile(), it creates a new file in you system's temporary directory.
• The temporary file is opened in binary mode (wb+) by default, and it can be read from and written to like any other file object.
• The temporary file is deleted as soon as it is closed. This is controlled by the delete parameter, which is True by default. This is important to set it True, as if not done then it could fill up the server's storage.

In our case, we have set delete=False, and we have override the FileResponse to add a __del__ method, which will be deleting the file once the response is sent (see: api/dependencies/repositories). Issue we were experiencing is because the temporary file was getting deleted as soon as it's closed, which happens when with block is exited. We were getting the following error RuntimeError: File at path /tmp/tmpuc5ru1oh.png does not exist. And this is expected behaviour when delete=True is set in tempfile.NamedTemporaryFile.

The following figure describes how the Preview in DocFlow works.

DocFlow allows, preview of only two media types, image/ and application/pdf.