Django2.0手册: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.

Note

In order to send email, Django requires a few settings telling it
how to connect to your mail server. At the very least, you’ll need
to specify EMAIL_HOST and possibly
EMAIL_HOST_USER and EMAIL_HOST_PASSWORD,
though other settings may be also required depending on your mail
server’s configuration. Consult the Django settings
documentation
for a full list of email-related
settings.

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.

See also

Server error emails are sent using the logging framework, so you can
customize this behavior by customizing your logging configuration.

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:

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.

Note

BrokenLinkEmailsMiddleware must appear
before other middleware that intercepts 404 errors, such as
LocaleMiddleware or
FlatpageFallbackMiddleware.
Put it towards the top of your MIDDLEWARE setting.

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.

See also

404 errors are logged using the logging framework. By default, these log
records are ignored, but you can use them for error reporting by writing a
handler and configuring logging appropriately.

Filtering error reports¶

Warning

Filtering sensitive data is a hard problem, and it’s nearly impossible to
guarantee that sensitive data won’t leak into an error report. Therefore,
error reports should only be available to trusted team members and you
should avoid transmitting error reports unencrypted over the Internet
(such as through email).

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
(**********).

See also

You can also set up custom error reporting by writing a custom piece of
exception middleware. If you do write custom
error handling, it’s a good idea to emulate Django’s built-in error handling
and only report/log errors if DEBUG is False.