Metadata-Version: 1.1
Name: django_uncertainty
Version: 1.2
Summary: A Django middleware to generate predictable errors on sites
Home-page: https://github.com/abarto/django_uncertainty
Author: Agustin Barto
Author-email: abarto@gmail.com
License: BSD
Description: django\_uncertainty
        ===================
        
        Introduction
        ------------
        
        ``django_uncertainty`` is a `Django <https://www.djangoproject.com/>`_ middleware that allows the
        developer to introduce controlled uncertainty into his or her site. The main purpose is providing a
        tool to reproduce less-than-ideal conditions in a local development environment to evaluate
        external actors might react when a Django site starts misbehaving.
        
        It requires `Django 1.10 <https://docs.djangoproject.com/en/1.10/releases/1.10/>`_ or later as it
        uses the new middleware framework.
        
        Installation
        ------------
        
        You can get ``django_uncertainty`` using pip:
        
        $ pip install django\_uncertainty
        
        If you want to install it from source, grab the git repository from
        GitHub and run setup.py:
        
        ::
        
            $ git clone git://github.com/abarto/django_uncertainty.git
            $ cd django_uncertainty
            $ python setup.py install
        
        Once the package has been installed, you need to add the middleware to
        your Django settings file:
        
        .. code:: python
        
            MIDDLEWARE = [
                'django.middleware.security.SecurityMiddleware',
                ...
                'uncertainty.UncertaintyMiddleware'
            ]
        
        Usage
        -----
        
        The middleware behaviour is controlled by the ``DJANGO_UNCERTAINTY`` Django setting. For example:
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(
                u.path_is('^/api'), u.random_choice([
                    (u.delay(u.default(), 5), 0.3), (u.server_error(), 0.2)]))
        
        This tells the middleware that if the request path starts with "/api", 30% of the time the request
        is going to be delayed by 5 seconds, 20% of the time the site is going to respond with a status 500
        (Server Error), and the rest of the time the site is going to function normally.
        
        The next section describes all the available behaviours and conditions.
        
        Behaviours
        ----------
        
        All behaviours are implemented as sub-classes of the ``Behaviour``
        class:
        
        .. code:: python
        
            class Behaviour:
                """Base of all behaviours. It is also the default implementation which just just returns the
                result of calling get_response."""
                def __call__(self, get_response, request):
                    """Returns the result of calling get_response (as given by the UncertaintyMiddleware
                    middleware with request as argument. It returns the same response that would have been
                    created by the Django stack without the introduction of UncertaintyMiddleware.
                    :param get_response: The get_response method provided by the Django stack
                    :param request: The request that triggered the middleware
                    :return: The result of calling get_response with the request parameter
                    """
                    response = get_response(request)
                    return response
        
        Behaviours work like functions that take the same parameters given the
        the Django middleware.
        
        default
        ~~~~~~~
        
        As the name implies, this is the default behaviour. It just makes the requests continue as usual
        through the Django stack. Using ``default`` is the same as omitting the ``DJANGO_UNCERTAINTY``
        setting altogether.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.default()
        
        html
        ~~~~
        
        Overrides the site's response with an arbitrary HTTP response. Without any arguments it returns a
        response with status code 200 (Ok). ``html`` takes the same arguments as Django's
        `HttpResponse <https://docs.djangoproject.com/en/1.10/ref/request-response/#django.http.HttpResponse>`_.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.html('<html><head></head><body><h1>Hello World!</h1></body></html>')
        
        ok
        ~~
        
        An alias for ``html``.
        
        bad\_request
        ~~~~~~~~~~~~
        
        Overrides the site's response with an HTTP response with status code 400 (Bad Request).
        ``bad_request`` takes the same arguments as Django's
        `HttpResponseBadRequest <https://docs.djangoproject.com/en/1.10/ref/request-response/#django.http.HttpResponseBadRequest>`_.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.bad_request('<html><head></head><body>Oops!</body></html>')
        
        forbidden
        ~~~~~~~~~
        
        Overrides the site's response with an HTTP response with status code 403 (Forbidden). ``forbidden``
        takes the same arguments as Django's
        `HttpResponseForbidden <https://docs.djangoproject.com/en/1.10/ref/request-response/#django.http.HttpResponseForbidden>`_.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.forbidden('<html><head></head><body>NOPE</body></html>')
        
        not\_allowed
        ~~~~~~~~~~~~
        
        Overrides the site's response with an HTTP response with status code 405 (Not Allowed).
        ``not_allowed`` takes the same arguments as Django's
        `HttpResponseNotAllowed <https://docs.djangoproject.com/en/1.10/ref/request-response/#django.http.HttpResponseNotAllowed>`_.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.not_allowed(permitted_methods=['PUT'], content='<html><head></head><body>NOPE</body></html>')
        
        not\_found
        ~~~~~~~~~~
        
        Overrides the site's response with an HTTP response with status code 404 (Not Found).
        ``not_found`` takes the same arguments as Django's
        `HttpResponse <https://docs.djangoproject.com/en/1.10/ref/request-response/#django.http.HttpResponse>`_.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.not_found(permitted_methods=['PUT'], content='<html><head></head><body>Who?</body></html>')
        
        server\_error
        ~~~~~~~~~~~~~
        
        Overrides the site's response with an HTTP response with status code 500 (Internal Server Error).
        ``server_error`` takes the same arguments as Django's
        `HttpResponseServerError <https://docs.djangoproject.com/en/1.10/ref/request-response/#django.http.HttpResponseServerError>`_.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.server_error('<html><head></head><body>BOOM</body></html>')
        
        status
        ~~~~~~
        
        Overrides the site's response with an HTTP response with a given status code.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.status(201, content='<html><head></head><body><h1>Created</h1></body></html>')
        
        json
        ~~~~
        
        Overrides the site's response with an arbitrary HTTP response with content type
        ``application/json``. Without any arguments it returns a response with status code 200 (Ok).
        ``json`` takes the same arguments as Django's
        `JsonResponse <https://docs.djangoproject.com/en/1.10/ref/request-response/#jsonresponse-objects>`_.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.json({'foo': 1, 'bar': True})
        
        delay
        ~~~~~
        
        Introduces a delay after invoking another behaviour. For example, this specifies a delay of half a
        second into the actual site responses:
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.delay(u.default(), 0.5)
        
        You can replace the first argument with any other valid behaviour.
        
        delay\_request
        ~~~~~~~~~~~~~~
        
        It is similar to ``delay``, but the delay is introduced *before* the specified behaviour is invoked.
        
        random\_choice
        ~~~~~~~~~~~~~~
        
        This is the work horse of ``django_uncertainty``. ``random_choice`` allows you to specify different
        behaviours that are going to be chosen at random (following the give proportions) when a request is
        received. It takes a list of behaviours or tuples of behaviours and proportions,
        
        For example, let's say we want 30% of the request to be responded with an Internal Server Error
        response, 20% with a Bad Request response, and the rest with the actual response but with a 1
        second delay. This can be specified as follows:
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.random_choice([(u.server_error(), 0.3), (u.bad_request(), 0.2), u.delay(u.default(), 1)])
        
        If proportions are specified, the total sum of them must be less than 1. If no proportions are
        specified, the behaviours are chosen with an even chance between them:
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.random_choice([u.server_error(), u.default()])
        
        This specifies that approximetly half the request are going to be responded with an Internal Server
        Error, and half will work normally.
        
        conditional
        ~~~~~~~~~~~
        
        It allows you to specify that a certain behaviour should be invoked only if a certain condition is
        met. If the condition is not met, the alternative behvaiour (which is ``default`` by default) is
        executed.
        
        ``python import uncertainty as u DJANGO_UNCERTAINTY = u.conditional(u.is_post, u.server_error())``
        
        The specification above states that if the request uses the POST method, the site should respond
        with an Internal Server Error. If you want to specify an alternative behaviour other than the
        default, use the ``alternative_behaviour`` argument:
        
        ``python import uncertainty as u DJANGO_UNCERTAINTY = u.conditional(u.is_post, u.server_error(), alternative_behaviour=u.delay(u.default(), 0.3)``
        
        Conditions can be combined using boolean operators. For instance,
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.conditional(u.is_authenticated or not u.is_get, u.bad_request())
        
        specifies that if the request is authenticated or if it uses the GET method, a Bad Request response
        should be used.
        
        In the next section, all the predefined conditions are presented.
        
        cond
        ~~~~
        
        An alias for ``conditional``.
        
        multi\_conditional
        ~~~~~~~~~~~~~~~~~~
        
        ``multi_conditional`` takes a list of condition/behaviour pairs, and when a request is received, it
        iterates over the conditions until one is met, and the corresponding behaviour is invoked. If no
        condition is met, the default behaviour is invoked.
        
        ``python import uncertainty as u DJANGO_UNCERTAINTY = u.multi_conditional([(u.is_get, u.delay(u.default(), 0.5), (u.is_post, u.server_error())])``
        
        The specification above states that if the request uses the GET method, it should be delayed by
        half a second, if it uses POST, it should respond with an Internal Server Error, and if neither of
        those conditions are met, the request should go through as usual.
        
        The default behaviour to be used when no conditions are met can be specified with the ``default_behaviour`` argument:
        
        ``python import uncertainty as u DJANGO_UNCERTAINTY = u.multi_conditional([(u.is_get, u.delay(u.default(), 0.5), (u.is_post, u.server_error())], default_behaviour=u.not_found())``
        
        multi\_cond
        ~~~~~~~~~~~
        
        An alias for ``cond``.
        
        case
        ~~~~
        
        An alias for ``case``.
        
        Custom behaviours
        ~~~~~~~~~~~~~~~~~
        
        We've done our best to implement behaviours that make sense in the context of introducing
        uncertainty into a Django site, however, if you need to implement your own behaviours, all you need
        to do is derive the ``Behaviour`` class. Let's say you want a Behaviour that adds a header to the
        response generated by another behaviour. Here's one possible implementation of such behaviour:
        
        .. code:: python
        
            class AddHeaderBehaviour(Behaviour):
                def __init__(self, behaviour, header_name, header_value):
                    self._behaviour = behaviour
                    self._header_name = header_name
                    self._header_value = header_value
        
                def __call__(self, get_response, request):
                    response = self._behaviour(get_response, request)
                    response[self._header_name] = self._header_value
        
                    return response
        
        If you think that there's a use case that we haven't covered that might be useful for other users,
        feel free to create an issue on `GitHub <https://github.com/abarto/django_uncertainty>`__.
        
        Conditions
        ----------
        
        Conditions are subclasses of the ``Predicate`` class:
        
        .. code:: python
        
            class Predicate:
                """Represents a condition that a Django request must meet. It is used in conjunction with
                ConditionalBehaviour to control if behaviours are invoked depending on the result of the
                Predicate invocation. Multiple predicates can be combined with or and and.
                """
                def __call__(self, get_response, request):
                    """Returns True for all calls.
                    :param get_response: The get_response method provided by the Django stack
                    :param request: The request that triggered the middleware
                    :return: True for all calls.
                    """
                    return True
        
        Whenever a conditional behaviour is used, the predicate is invoked with the same parameters that
        would be given the the behaviour.
        
        is\_method
        ~~~~~~~~~~
        
        The condition is met if the request uses the specified method.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(u.is_method('PATCH'), u.not_allowed())
        
        is\_get
        ~~~~~~~
        
        The condition is met if the request uses the GET HTTP method.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(u.is_get, u.not_allowed())
        
        is\_delete
        ~~~~~~~~~~
        
        The condition is met if the request uses the DELETE HTTP method.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(u.is_delete, u.not_allowed())
        
        is\_post
        ~~~~~~~~
        
        The condition is met if the request uses the POST HTTP method.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(u.is_post, u.not_allowed())
        
        is\_put
        ~~~~~~~
        
        The condition is met if the request uses the PUT HTTP method.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(u.is_put, u.not_allowed())
        
        has\_parameter
        ~~~~~~~~~~~~~~
        
        The condition is met if the request has the given parameter.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(u.has_parameter('q'), u.server_error())
        
        has\_param
        ~~~~~~~~~~
        
        An alias for ``has_parameter``
        
        path\_is
        ~~~~~~~~
        
        The condition is met if the request path matches the given regular expression.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(u.path_is('^/api'), u.delay(u.default(), 0.2))
        
        is\_authenticated
        ~~~~~~~~~~~~~~~~~
        
        The condition is met if the user has authenticated itself.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(u.is_authenticated, u.not_found())
        
        user\_is
        ~~~~~~~~
        
        The condition is met if the authenticated user has the given username.
        
        .. code:: python
        
            import uncertainty as u
            DJANGO_UNCERTAINTY = u.cond(u.user_is('admin', u.forbidden())
        
        Custom conditions
        ~~~~~~~~~~~~~~~~~
        
        As with behaviours, custom conditions are creating deriving the ``Predicate`` class. Let's say you
        want a condition that checks the presence of a header in the request. Here's one possible
        implementation of such condition:
        
        .. code:: python
        
            class HasHeaderPredicate(Predicate):
                def __index__(self, header_name):
                    self._header_name = header_name
        
                def __call__(self, get_response, request):
                    return self._header_name in request
        
        Feedback
        --------
        
        All feedback is appreciated, so if you found problems or have ides for new features, just create an
        issue on `GitHub <https://github.com/abarto/django_uncertainty>`_.
        
Platform: UNKNOWN
Classifier: Development Status :: 4 - Beta
Classifier: Environment :: Web Environment
Classifier: Framework :: Django
Classifier: Intended Audience :: Developers
Classifier: License :: OSI Approved :: MIT License
Classifier: Operating System :: OS Independent
Classifier: Programming Language :: Python
Classifier: Programming Language :: Python :: 2
Classifier: Programming Language :: Python :: 3
Classifier: Topic :: Utilities
