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Sometimes I just love how the open source community works nowadays! Sometimes you  use your favourite search engine to find a package/repository/etc..., just to find out thatit contains a quickstart info, a proper package.json or docker-compose.yml. All you need to do is "npm install && npm run" or "docker-compose build && docker-compose up" and you are good to go.

This helps devs to contribute to open source software soooooo much!

TL;DR: Use Docker, package.json, requirements.txt, and for the love of god, write a Quickstart section into your Readme!

If you have ever gotten this error with your mod passenger installation:

$ passenger-config restart-app
*** ERROR: Phusion Passenger doesn't seem to be running. If you are sure that it
is running, then the causes of this problem could be one of:

1. You customized the instance registry directory using Apache's
 PassengerInstanceRegistryDir option, Nginx's
 passenger_instance_registry_dir option, or Phusion Passenger Standalone's
 --instance-registry-dir command line argument. If so, please set the
 environment variable PASSENGER_INSTANCE_REGISTRY_DIR to that directory
 and run this command again.
 2. The instance directory has been removed by an operating system background
 service. Please set a different instance registry directory using Apache's
 PassengerInstanceRegistryDir option, Nginx's passenger_instance_registry_dir
 option, or Phusion Passenger Standalone's --instance-registry-dir command
 line argument.

Then you most likely have SystemD running, which uses PrivateTmp folders instead of /tmp folders.

It's annoying, but easy to fix, see this blog post:
https://www.pistolfly.com/weblog/en/2016/01/passenger-config-and-passenger-status-result-in-an-error-on-centos7.html

Inspired by a recent commitstrip: http://www.commitstrip.com/en/2017/05/06/bugs-of-the-future/

Like almost everyone else I had to test my Single Page AngularJS Application, which uses Django Rest Framework as a Backend, with Internet Explorer (11, thankfully). While my SPA works fine in Chrome and Firefox, it does not work very well in Internet Explorer (shocking, lmao).

Anyway, the obvious errors, ranging from needing polyfils to some CSS quirks, were fixed quickly.

But at some point I noticed: Why the hell are changes I make via PUT/POST/PATCH not shown when I make a GET request (retrieving all instances of a model) to the same endpoint afterwards? It kept returning the same data again and again. Where the hell did my changes go? Is my database broken? Is Internet Explorer not firing the PUT/POST/PATCH calls properly?

None of that was true. As it turns out, Internet Explorer 11 caches almost all GET requests to my REST API. I submit a change, I reload the page, and the change has disappeared. Caching at its best.

So I googled and stackoverflowed (is that a word?), and I found some people talking about cache headers. And they are god damn right... Django aswell as Django Rest Framework do not set any cache headers in the response (most likely for a good reason, better be explicit than implicit).

So I tried a couple of the provided solutions, and I must say, I was really unhappy with those approaches. They were either very repetitive (like the ``@never_cache`` decorator added to all my viewsets), or required monkey patches and other sorts of things that I do not like to see. Btw, a cache buster within my JavaScript SPA was a no-go for me.

So I thought to myself: How about I make my whole Django Rest Framework Application "uncachable"? And so I did, with a very few lines of code and as a Django Middleware:

from django.utils.cache import add_never_cache_headers

class DisableClientSideCachingMiddleware(object):
    """
    Internet Explorer / Edge tends to cache REST API calls, unless some specific HTTP headers are added by our
    application.

    - no_cache
    - no_store
    - must_revalidate
    """
    def process_response(self, request, response):
        add_never_cache_headers(response)
        return response

Don't forget to also add this middleware to your settings.

MIDDLEWARE_CLASSES = (
    ...
    'yourapp.middlewares.DisableClientSideCachingMiddleware',
)

Please note that this disables caching of ALL requests coming to your Django Application. If you are serving static files from your Django Application (instead of serving them directly from your webserver), this will affect your performance.

This middleware works for me. I later discovered that somebody else has already had a similar idea, too. The obvious disadvantage here is that it disables caching for all parts of my Django Application. This is fine for me, as I am only using Django Rest Framework and I do not want caching on client side to happen at all, but it might not be okay for some other applications.

Nevertheless, I hope this piece of code helps people that have similar problems. Also, please feel free to share your experiences and solutions to such caching problems with Internet Explorer.

Django has an interesting default behaviour for NullBooleanFields, which are used by django_filters BooleanFilter. While the String 'True' evaluates to Python Boolean True, and the String 'False' evaluates to Python Boolean False, this is not happening for the lowercase variants 'true' and 'false'. This is kind of annoying when you are using DJango Rest Filters, where you would have a REST API call like this (e.g., when calling from JavaScript):

GET /tasks/?show_only_my_tasks=true

This does not work as expected, as "show_only_my_tasks=true" evaluates to "None".

The correct usage according to Djangos NullBooleanField would have been this:

GET /tasks/?show_only_my_tasks=True

To overcome this issue, you can use the following code snippet:

class BetterBooleanSelect(NullBooleanSelect):
    """
    Djangos NullBooleanSelect does not evaluate 'true' to True, and not 'false' to False
    This overwritten NullBooleanSelect allows that
    See https://code.djangoproject.com/ticket/22406#comment:3
    """
    def value_from_datadict(self, data, files, name):
        value = data.get(name)
        return {
            '2': True,
            True: True,
            'true': True,  # added, as NullBooleanSelect does not do that
            'True': True,
            '3': False,
            'false': False,  # added, as NullBooleanSelect does not do that
            'False': False,
            False: False,
        }.get(value)


class BetterBooleanField(forms.NullBooleanField):
    """
    Better Boolean Field that also evalutes 'false' to False and 'true' to True
    """
    widget = BetterBooleanSelect

    def clean(self, value):
        return super(BetterBooleanField, self).clean(value)


class BetterBooleanFilter(django_filters.BooleanFilter):
    """
    This boolean filter allows evaluating 'true' and 'false'
    """
    field_class = BetterBooleanField

In your REST Filter you then only need to write this:

class TaskFilter(BaseFilter):
    """ Filter for Tasks """
    class Meta:
        model = Task

    show_only_my_tasks = BetterBooleanFilter()

I have created a special page with a Monero JavaScript Miner using CoinHive.

You can start the miner if you visit this page (and this page only): https://chkr.at/miner/

Note: Monero is something like Bitcoin, except for that it can be mined in a browser. I am using this as a way to allow people to say thank you.

If you want to learn more about mining Monero with coin-hive, I would like to direct you to this YouTube Video (not made by me):