Tutorial should have include ALLOWED_HOSTS setting

[anonymous]

Got bit by 500 errors when switching to DEBUG=False.

As a total newbie, this was tough because a local install on my mac wasn't sending me email by default either.

I would recommend updating the tutorial to mention setting ALLOWED_HOSTS within the initial settings.py setup, perhaps to 127.0.0.1/localhost if the user is doing a local install.

[Carl Meyer]

I'm hesitant to add extra verbiage at that stage of the tutorial involving something that you don't actually need until much later, whenever you try flipping DEBUG to False. I was hoping that having DEBUG and ALLOWED_HOSTS very close to each other in the template settings file, and a comment on ALLOWED_HOSTS saying "required if DEBUG is False", would be enough - but apparently it isn't. Maybe we could add another comment above the DEBUG setting in settings.py specifically reminding you to check ALLOWED_HOSTS if you flip it to False?

Accepting because I think this is a problem that should be solved; not sure yet if adding to the tutorial is the right solution.

[Russell Keith-Magee]

Agreed that this is a problem that needs to be solved; equally hesitant about adding it to the early tutorials.

One possible approach would be to tackle an old feature request, and write a new tutorial on deployment. This would also give us a chance to set some best practices on "how to do it right", which is something that we've historically punted on. It's sure to be a bike shed discussion, but with a couple of judicious BDFL judgements, I'm sure we could get something we can all live with.

[Carl Meyer]

Is there an existing ticket for "deployment tutorial"? #19697 is at least closely related.

[Tim Graham]

This was also suggested in #20139.

[Carl Meyer]

#20171 suggests adding documentation under DEBUG noting that if you set it False you must set ALLOWED_HOSTS. It also contains a list of related tickets:

• #19866
• #19946
• #20120
• #20139
• #20148
• #20164
• #20171

[Tim Graham]

Suggested again in #20239.

[Fang Jun]

Made a patch for docs/topics/settings.txt

[Tim Graham]

Current status of this:

1. The ​deployment checklist has a note about ALLOWED_HOSTS.
2. The ALLOWED_HOSTS comment in the default project template was removed (probably in Aymeric's effort to simplify it). I've added it back in the attached patch as well as other relevant warnings in a couple places.
3. I like the idea offered in #20139: "Whenever starting the server in DEBUG = False and ALLOWED_HOSTS = [], display a warning on the console (stderr) that no request will be served because of the empty ALLOWED_HOSTS setting." If someone agrees, we can open a new ticket.

[Aymeric Augustin]

AFAIK it's a conscious choice not to talk about anything related to deployment (like ALLOWED_HOSTS) in the tutorial. The tutorial must stay focused on its main purpose; it mustn't be a default place for docs that don't fit anywhere else.

I strongly believe that insufficient information is worse than no information at all, and for this reason I would really like if we could keep settings.py as is (although I don't have much hope and I'm pretty sure settings.py will grow some cruft again; well, at least I'll voice my opposition).

There's tons of useful advice to give about deployment; the deployment checklist helps much more than random, piecemeal advice in settings.py. I have to admit that I don't care very much about users who can't be bothered to read the docs, too.

[Tim Graham]

The tutorial talks about setting DEBUG to False in order to use your own 404.html, 500.html, etc. templates. The note appears right under that section so if people try it they will be aware.

I'm fine with keeping settings.py as is.

What do you think about the suggestion of modifying runserver so it won't work with a bad configuration? I feel like that should eliminate this problem for non-deployment cases.

[Daniele Procida]

I think the console should warn the user, if ALLOWED_HOSTS is empty, that it will mean the site won't work when DEBUG is False (whatever the current state of DEBUG).

It's caught me out more than once...

[Tim Graham]

New patch adds logic so runserver won't serve any requests if DEBUG is False and ALLOWED_HOSTS is empty (I'm unsure if this needs tests -- tests.admin_scripts.ManageRunserver mocks the run method so I don't think anything in that method is actually tested).

Also removed the note in the previous patch from settings.py.

[Claude Paroz]

Small nitpick about self.stderr.write/exit, I think that this could be replaced by raising CommandError instead.

[Tim Graham]

Thanks, updated in a pull request. Moved the logic to the handle() method and also added a test. ​https://github.com/django/django/pull/1249

[Tim Graham <timograham@…>]

In 4e94c84e50b960405d5708d8d9528c44c7dabe83:

Fixed #19875 - Added warnings regarding DEBUG=False and empty ALLOWED_HOSTS

[Tim Graham <timograham@…>]

In 46dacb5bb157ff78e21c19f1f1b109edf378ddcb:

[1.5.x] Fixed #19875 - Added warnings regarding DEBUG=False and empty ALLOWED_HOSTS

Backport of 4e94c84e50 from master

[Tim Graham <timograham@…>]

In 96c71d423db13825869a929b25d6b83dde67c170:

Added runserver validation to detect if DEBUG=False and ALLOWED_HOSTS is empty.

Refs #19875.