Django表单不在生产服务器上呈现 - 使用testserver在本地工作正常，并且单元测试在生产服务器上传递

Question

This might be the strangest error I have ever come accross in my short time as a developer. I have a form that renders perfectly well on my local machine, but the exact same code fails to render on the server.

I have a form, that looks like this:

Nothing fancy, just a few input fields and a submit button.

How did I create it? Well firstly there's a form:

from django import forms
from django.forms.extras.widgets import SelectDateWidget
from blog.models import BlogPost

EMPTY_FIELD_ERROR = "You cannot submit a blog post with no %s"


class DateInput(forms.DateInput):
    input_type = 'date'



class PlainTextarea(forms.Textarea):

    def build_attrs(self, extra_attrs=None, **kwargs):
        attrs = super(PlainTextarea, self).build_attrs(extra_attrs, **kwargs)
        if "cols" in attrs: del attrs["cols"]
        if "rows" in attrs: del attrs["rows"]
        return attrs



class BlogPostForm(forms.models.ModelForm):


    class Meta:
        model = BlogPost
        fields = ("title", "date", "body", "visible")
        widgets = {
         "title": forms.fields.TextInput(attrs={
          "class": "pure-u-1-1 pure-u-md-19-24"
         }),
         "date": DateInput(),
         "body": PlainTextarea(attrs={
          "class": "pure-u-1-1 pure-u-md-19-24"
         }),
         "visible": forms.CheckboxInput(attrs={
          "class": "pure-u-1-24"
         })
        }
        error_messages = {
         "title": {"required": EMPTY_FIELD_ERROR % "title"},
         "date": {"required": EMPTY_FIELD_ERROR % "date"},
         "body": {"required": EMPTY_FIELD_ERROR % "body"}
        }

In the new_post view, if it detects that the request is a GET request, I simply make an instance of this form, and pass it to the new_post template:

def new_post_page(request):
    if request.method == "POST":
        form = BlogPostForm(request.POST)
        if form.is_valid():
            BlogPost.objects.create(
             title=request.POST["title"].strip(),
             date=datetime.datetime.strptime(
              request.POST["date"], "%Y-%m-%d"
             ).date(),
             body=request.POST["body"].strip(),
             visible=request.POST.get("visible") is not None
            )
            return redirect("/")
        else:
            return render(request, "new_post.html", {"form": form})
    form = BlogPostForm()
    return render(request, "new_post.html", {"form": form})

And here's a section of the template:

<form method="POST" class="pure-form pure-form-aligned">
  <div class="pure-g">
    <div class="pure-u-1-1 formrow">
      <label for="{{ form.title.id_for_label }}" class="pure-u-1-1 pure-u-md-4-24">Title:</label>
      {{ form.title }}
      {% if form.title.errors %}
      <div class="error">
        {{ form.title.errors }}
      </div>
      {% endif %}
    </div>
    <div class="pure-u-1-1 formrow">
      <label for="{{ form.date.id_for_label }}" class="pure-u-1-1 pure-u-md-4-24">Date:</label>
      {{ form.date }}
      {% if form.date.errors %}
      <div class="error">
        {{ form.date.errors }}
      </div>
      {% endif %}
    </div>

This all works fine on my own machine (MacBook, El Capitain, Python3, Django 1.8.4), but when I deploy the code to the server, I get this:

Inspecting the HTML shows that the {{form.title}} tags have not rendered. But everything is the same! Well mostly everything. Obviously some settings are different on the server such as Debug being set to False. I also use a postgres database on the server, and an SQLite database locally.

To make things even more maddening, I have unit tests, including tests that the new_page view is rendering the form - and they pass on the server! I even started a Django shell on the server, manually passed a request to the new_page view, printed the HTML, and the input HTML was there !

Some information that might be useful:

• The server uses nginx, which sends requests to gunicorn. The OS is Ubuntu 14.04.
• The form was rendering perfectly well back when it was all HTML, before I connected it to a Django form
• I have applied all migrations - there were no new ones to apply but a migration happens automatically whenever I deploy.

Please help this Django novice?

UPDATE

I have tried using the django testserver in place of gunicorn, and that renders the form correctly, so it could be a problem with gunicorn?

Answer 1

In case another poor soul ends up here. Check that your packages (pip freeze) are the same locally and on the server. I had django-filter==0.15.0 locally and django-filter==0.10.0 on the server which was causing this exact issue with no errors being raised.

Answer 2

So, I have resolved the problem. Unfortunately I'm not entirely sure how.

As I mentioned in my update, turning off gunicorn and using the django test server instead fixed the issue. I shut down the testserver and fired up gunicorn again, and... the forms were still rendering correctly.

My suspicion is that restarting gunicorn was all that was needed. I don't know why, or if that was definitely what fixed it. Oh well.

Answer 3

I had the same issue when I deployed my django project to AWS EC2.

If you've followed Nginx gunicorn and Django tutorials your best option is to reboot the EC2 and then restart the gunicorn server. This has solved my issue.

Answer 4

You should restart your web sever every time you deploy - that will make sure you are running the latest code for your app. It's very deceptive because it will correctly pull the html templates, but not run the code that renders the content for the templates (that's why you're seeing your labels which are hard-coded but not the text inputs which are rendered dynamically).

I use Apache on Ubuntu and this gets me every once in a while when I've been up all night debugging something...Always restart your server when you deploy fresh code:

sudo service apache2 restart