Error reporting

When you’re running a public site you should always turn off the DEBUG setting. That will make your server run much faster, and will also prevent malicious users from seeing details of your application that can be revealed by the error pages.

However, running with DEBUG set to False means you’ll never see errors generated by your site – everyone will just see your public error pages. You need to keep track of errors that occur in deployed sites, so Django can be configured to create reports with details about those errors.

Email reports

Server errors

When DEBUG is False, Django will email the users listed in the ADMINS setting whenever your code raises an unhandled exception and results in an internal server error (HTTP status code 500). This gives the administrators immediate notification of any errors. The ADMINS will get a description of the error, a complete Python traceback, and details about the HTTP request that caused the error.

By default, Django will send email from root@localhost. However, some mail providers reject all email from this address. To use a different sender address, modify the SERVER_EMAIL setting.

To activate this behavior, put the email addresses of the recipients in the ADMINS setting.

404 errors

Django can also be configured to email errors about broken links (404 “page not found” errors). Django sends emails about 404 errors when:

• DEBUG is False;
• Your MIDDLEWARE_CLASSES setting includes django.middleware.common.BrokenLinkEmailsMiddleware.

If those conditions are met, Django will email the users listed in the MANAGERS setting whenever your code raises a 404 and the request has a referer. It doesn’t bother to email for 404s that don’t have a referer – those are usually just people typing in broken URLs or broken Web bots. It also ignores 404s when the referer is equal to the requested URL, since this behavior is from broken Web bots too.

You can tell Django to stop reporting particular 404s by tweaking the IGNORABLE_404_URLS setting. It should be a list of compiled regular expression objects. For example:

import re
IGNORABLE_404_URLS = [
    re.compile(r'\.(php|cgi)$'),
    re.compile(r'^/phpmyadmin/'),
]

In this example, a 404 to any URL ending with .php or .cgi will not be reported. Neither will any URL starting with /phpmyadmin/.

The following example shows how to exclude some conventional URLs that browsers and crawlers often request:

import re
IGNORABLE_404_URLS = [
    re.compile(r'^/apple-touch-icon.*\.png$'),
    re.compile(r'^/favicon\.ico$'),
    re.compile(r'^/robots\.txt$'),
]

(Note that these are regular expressions, so we put a backslash in front of periods to escape them.)

If you’d like to customize the behavior of django.middleware.common.BrokenLinkEmailsMiddleware further (for example to ignore requests coming from web crawlers), you should subclass it and override its methods.

Filtering error reports

Filtering sensitive information

Error reports are really helpful for debugging errors, so it is generally useful to record as much relevant information about those errors as possible. For example, by default Django records the full traceback for the exception raised, each traceback frame’s local variables, and the HttpRequest’s attributes.

However, sometimes certain types of information may be too sensitive and thus may not be appropriate to be kept track of, for example a user’s password or credit card number. So in addition to filtering out settings that appear to be sensitive as described in the DEBUG documentation, Django offers a set of function decorators to help you control which information should be filtered out of error reports in a production environment (that is, where DEBUG is set to False): sensitive_variables() and sensitive_post_parameters().

sensitive_variables(*variables) [source]

If a function (either a view or any regular callback) in your code uses local variables susceptible to contain sensitive information, you may prevent the values of those variables from being included in error reports using the sensitive_variables decorator:

from django.views.decorators.debug import sensitive_variables

@sensitive_variables('user', 'pw', 'cc')
def process_info(user):
    pw = user.pass_word
    cc = user.credit_card_number
    name = user.name
    ...

In the above example, the values for the user, pw and cc variables will be hidden and replaced with stars (**********) in the error reports, whereas the value of the name variable will be disclosed.

To systematically hide all local variables of a function from error logs, do not provide any argument to the sensitive_variables decorator:

@sensitive_variables()
def my_function():
    ...

When using multiple decorators

If the variable you want to hide is also a function argument (e.g. ‘user’ in the following example), and if the decorated function has multiple decorators, then make sure to place @sensitive_variables at the top of the decorator chain. This way it will also hide the function argument as it gets passed through the other decorators:

@sensitive_variables('user', 'pw', 'cc')
@some_decorator
@another_decorator
def process_info(user):
    ...

sensitive_post_parameters(*parameters) [source]

If one of your views receives an HttpRequest object with POST parameters susceptible to contain sensitive information, you may prevent the values of those parameters from being included in the error reports using the sensitive_post_parameters decorator:

from django.views.decorators.debug import sensitive_post_parameters

@sensitive_post_parameters('pass_word', 'credit_card_number')
def record_user_profile(request):
    UserProfile.create(
        user=request.user,
        password=request.POST['pass_word'],
        credit_card=request.POST['credit_card_number'],
        name=request.POST['name'],
    )
    ...

In the above example, the values for the pass_word and credit_card_number POST parameters will be hidden and replaced with stars (**********) in the request’s representation inside the error reports, whereas the value of the name parameter will be disclosed.

To systematically hide all POST parameters of a request in error reports, do not provide any argument to the sensitive_post_parameters decorator:

@sensitive_post_parameters()
def my_view(request):
    ...

All POST parameters are systematically filtered out of error reports for certain django.contrib.auth.views views (login, password_reset_confirm, password_change, and add_view and user_change_password in the auth admin) to prevent the leaking of sensitive information such as user passwords.

Custom error reports

All sensitive_variables() and sensitive_post_parameters() do is, respectively, annotate the decorated function with the names of sensitive variables and annotate the HttpRequest object with the names of sensitive POST parameters, so that this sensitive information can later be filtered out of reports when an error occurs. The actual filtering is done by Django’s default error reporter filter: django.views.debug.SafeExceptionReporterFilter. This filter uses the decorators’ annotations to replace the corresponding values with stars (**********) when the error reports are produced. If you wish to override or customize this default behavior for your entire site, you need to define your own filter class and tell Django to use it via the DEFAULT_EXCEPTION_REPORTER_FILTER setting:

DEFAULT_EXCEPTION_REPORTER_FILTER = 'path.to.your.CustomExceptionReporterFilter'

You may also control in a more granular way which filter to use within any given view by setting the HttpRequest’s exception_reporter_filter attribute:

def my_view(request):
    if request.user.is_authenticated():
        request.exception_reporter_filter = CustomExceptionReporterFilter()
    ...

Your custom filter class needs to inherit from django.views.debug.SafeExceptionReporterFilter and may override the following methods:

class SafeExceptionReporterFilter [source]

SafeExceptionReporterFilter.is_active(request) [source]

Returns True to activate the filtering operated in the other methods. By default the filter is active if DEBUG is False.

SafeExceptionReporterFilter.get_post_parameters(request) [source]

Returns the filtered dictionary of POST parameters. By default it replaces the values of sensitive parameters with stars (**********).

SafeExceptionReporterFilter.get_traceback_frame_variables(request, tb_frame) [source]

Returns the filtered dictionary of local variables for the given traceback frame. By default it replaces the values of sensitive variables with stars (**********).