running a dash app below a segment (e.g. http://corporateserver.com/approotisreallythere)

[zogzog]

Hi all,

In some setups (corporate env ...) we have no choice but to run a dash app under an application-specific segment. I believe this is currently not supported.

While a specific nginx / wsgi combo is currently used to inform the flask app of this condition, it does not work for dash as the web client routes are configured before the first http request is seen (in dash.__init__).

This hack can be seen there : http://flask.pocoo.org/snippets/35/

Here is the patch I've written to clear the issue on dash side:

diff -r deb1dcee1e55 dash/dash.py
--- a/dash/dash.py      Mon Dec 11 22:56:31 2017 -0600
+++ b/dash/dash.py      Wed Dec 20 12:35:20 2017 +0100
@@ -24,6 +24,7 @@
         server=None,
         static_folder=None,
         url_base_pathname='/',
+        request_pathname_prefix=None,
         **kwargs
     ):

@@ -43,7 +44,7 @@
         self.config = _AttributeDict({
             'suppress_callback_exceptions': False,
             'routes_pathname_prefix': url_base_pathname,
-            'requests_pathname_prefix': url_base_pathname
+            'requests_pathname_prefix': request_pathname_prefix or url_base_pathname
         })

         # list of dependencies

This is quite simple and might be enough. To make it more transparent would probably demand much more work I think.

Opinions ?

[chriddyp]

Right now, this is done through the config like

app = dash.Dash()
app.config.update({
    'requests_pathname_prefix': ...
})

or

app = dash.Dash()
app.config.requests_pathname_prefix = '...'
})

However, as you mention, this isn't really well documented at all.

I'd prefer a solution that would generically handle all of the config options and maybe enforce a "standard way" of doing this. I see a couple of solutions:
1 - Remove the keyword arguments and move them all to config and document these better
2 - Move all of the config arguments as explicit keyword arguments in dash.Dash(...) and keep them as config

I think 2 seems like a reasonable approach to me, however the call signature might become really huge over time. That might not be a bad thing (for example, I actually like the huge call signature of pd.read_csv)

[zogzog]

Ah yes indeed I almost saw this :) Thanks for the clarification.