Flask unable to receive chunked data
Did you write both of the js upload file code and the flask in backend to handle upload request? If not then you will need some help with js to upload it.
One way to achieve chucked data upload is:

Chucked that file in the frontend with js. Give it some headers in the request for the total size, number of the chunk, chunk size... and send each chuck in a separate POST request (You can use dropzone.js for example, they will do the job for you, just need to config the params) 
In the backend, create an upload API which will read the request headers and merge the file chunks back together
I am kinda newby in python thus the question. 
I am trying to create a simple http web server that can receive chunked data from a post request. 
I have realized later that once a request sends a headers with chunked data, the Content-length headers will be set to zero, thus reading the sent data with 'request.get_data()' will fail.
Is there another way of reading the chunked data?
The request I receive does give me the data length in the 'X-Data-Length' headers.