Preferred method for downloading a file generated on the fly in Flask

Are you running the flask app behind a front end web server such as nginx or apache (which would be the best way to handle the downloading of files). If you're using nginx you can use the 'X-Accel-Redirect' header. For this example I'll use the directory /srv/static/reports as the directory you're creating the zipfiles in and wanting to serve them out of.

nginx.conf

in the server section

server {  # add this to your current server config  location /reports/ {    internal;    root /srv/static;  }}

your flask method

send the header to nginx to server

from flask import make_response@app.route('/download', methods=['GET','POST'])def download():    error=None    # ..    if request.method == 'POST':      if download_list == None or len(download_list) < 1:          error = 'No files to download'          return render_template('download.html', error=error, download_list=download_list)      else:          timestamp = dt.now().strftime('%Y%m%d:%H%M%S')          zfname = 'reports-' + str(timestamp) + '.zip'          zf = zipfile.ZipFile(downloaddir + zfname, 'a')          for f in download_list:              zf.write(downloaddir + f, f)          zf.close()          # TODO: remove zipped files, move zip to archive          # tell nginx to server the file and where to find it          response = make_response()          response.headers['Cache-Control'] = 'no-cache'          response.headers['Content-Type'] = 'application/zip'          response.headers['X-Accel-Redirect'] = '/reports/' + zf.filename          return response

If you're using apache, you can use their sendfile directive http://httpd.apache.org/docs/2.0/mod/core.html#enablesendfile