      # Get an instance of a specific named logger
      logger = logging.getLogger('project.interesting.stuff')
  
  The dotted paths of logger names define a hierarchy. The
  ``project.interesting`` logger is considered to be a parent of the
  ``project.interesting.stuff`` logger; the ``project`` logger
  is a parent of the ``project.interesting`` logger.
  
 
</s> remove Django logging extension reference
==================================

Django provides a number of utilities to handle the unique
requirements of logging in a web server environment.

Loggers
-------

Django provides several built-in loggers.

.. _django-logger:

``django``
~~~~~~~~~~

The catch-all logger for messages in the  ``django`` hierarchy. No messages are
posted using this name but instead using one of the loggers below.

.. _django-request-logger:

``django.request``
~~~~~~~~~~~~~~~~~~

Log messages related to the handling of requests. 5XX responses are
raised as ``ERROR`` messages; 4XX responses are raised as ``WARNING``
messages. Requests that are logged to the ``django.security`` logger aren't
logged to ``django.request``.

Messages to this logger have the following extra context:

* ``status_code``: The HTTP response code associated with the
  request.

* ``request``: The request object that generated the logging
  message.

.. _django-server-logger:

``django.server``
~~~~~~~~~~~~~~~~~

Log messages related to the handling of requests received by the server invoked
by the :djadmin:`runserver` command. HTTP 5XX responses are logged as ``ERROR``
messages, 4XX responses are logged as ``WARNING`` messages, and everything else
is logged as ``INFO``.

Messages to this logger have the following extra context:

* ``status_code``: The HTTP response code associated with the request.

* ``request``: The request object that generated the logging message.

.. _django-template-logger:

``django.template``
~~~~~~~~~~~~~~~~~~~

Log messages related to the rendering of templates.

* Missing context variables are logged as ``DEBUG`` messages.

.. _django-db-logger:

``django.db.backends``
~~~~~~~~~~~~~~~~~~~~~~

Messages relating to the interaction of code with the database. For example,
every application-level SQL statement executed by a request is logged at the
``DEBUG`` level to this logger.

Messages to this logger have the following extra context:

* ``duration``: The time taken to execute the SQL statement.
* ``sql``: The SQL statement that was executed.
* ``params``: The parameters that were used in the SQL call.

For performance reasons, SQL logging is only enabled when
``settings.DEBUG`` is set to ``True``, regardless of the logging
level or handlers that are installed.

This logging does not include framework-level initialization (e.g.
``SET TIMEZONE``) or transaction management queries (e.g. ``BEGIN``,
``COMMIT``, and ``ROLLBACK``). Turn on query logging in your database if you
wish to view all database queries.

.. _django-security-logger:

``django.security.*``
~~~~~~~~~~~~~~~~~~~~~~

The security loggers will receive messages on any occurrence of
:exc:`~django.core.exceptions.SuspiciousOperation` and other security-related
errors. There is a sub-logger for each subtype of security error, including all
``SuspiciousOperation``\s. The level of the log event depends on where the
exception is handled.  Most occurrences are logged as a warning, while
any ``SuspiciousOperation`` that reaches the WSGI handler will be logged as an
error. For example, when an HTTP ``Host`` header is included in a request from
a client that does not match :setting:`ALLOWED_HOSTS`, Django will return a 400
response, and an error message will be logged to the
``django.security.DisallowedHost`` logger.

These log events will reach the ``django`` logger by default, which mails error
events to admins when ``DEBUG=False``. Requests resulting in a 400 response due
to a ``SuspiciousOperation`` will not be logged to the ``django.request``
logger, but only to the ``django.security`` logger.

To silence a particular type of ``SuspiciousOperation``, you can override that
specific logger following this example::

    'handlers': {
        'null': {
            'class': 'logging.NullHandler',
        },
    },
    'loggers': {
        'django.security.DisallowedHost': {
            'handlers': ['null'],
            'propagate': False,
        },
    },

Other ``django.security`` loggers not based on ``SuspiciousOperation`` are:

* ``django.security.csrf``: For :ref:`CSRF failures <csrf-rejected-requests>`.

``django.db.backends.schema``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Logs the SQL queries that are executed during schema changes to the database by
the :doc:`migrations framework </topics/migrations>`. Note that it won't log the
queries executed by :class:`~django.db.migrations.operations.RunPython`.
Messages to this logger have ``params`` and ``sql`` in their extra context (but
unlike ``django.db.backends``, not duration). The values have the same meaning
as explained in :ref:`django-db-logger`.

Handlers
--------

Django provides one log handler in addition to those provided by the
Python logging module.

.. class:: AdminEmailHandler(include_html=False, email_backend=None, reporter_class=None)

    This handler sends an email to the site :setting:`ADMINS` for each log
    message it receives.

    If the log record contains a ``request`` attribute, the full details
    of the request will be included in the email. The email subject will
    include the phrase "internal IP" if the client's IP address is in the
    :setting:`INTERNAL_IPS` setting; if not, it will include "EXTERNAL IP".

    If the log record contains stack trace information, that stack
    trace will be included in the email.

    The ``include_html`` argument of ``AdminEmailHandler`` is used to
    control whether the traceback email includes an HTML attachment
    containing the full content of the debug Web page that would have been
    produced if :setting:`DEBUG` were ``True``. To set this value in your
    configuration, include it in the handler definition for
    ``django.utils.log.AdminEmailHandler``, like this::

        'handlers': {
            'mail_admins': {
                'level': 'ERROR',
                'class': 'django.utils.log.AdminEmailHandler',
                'include_html': True,
            }
        },

    Be aware of the :ref:`security implications of logging
    <logging-security-implications>` when using the ``AdminEmailHandler``.

    By setting the ``email_backend`` argument of ``AdminEmailHandler``, the
    :ref:`email backend <topic-email-backends>` that is being used by the
    handler can be overridden, like this::

        'handlers': {
            'mail_admins': {
                'level': 'ERROR',
                'class': 'django.utils.log.AdminEmailHandler',
                'email_backend': 'django.core.mail.backends.filebased.EmailBackend',
            }
        },

    By default, an instance of the email backend specified in
    :setting:`EMAIL_BACKEND` will be used.

    The ``reporter_class`` argument of ``AdminEmailHandler`` allows providing
    an ``django.views.debug.ExceptionReporter`` subclass to customize the
    traceback text sent in the email body. You provide a string import path to
    the class you wish to use, like this::

        'handlers': {
            'mail_admins': {
                'level': 'ERROR',
                'class': 'django.utils.log.AdminEmailHandler',
                'include_html': True,
                'reporter_class': 'somepackage.error_reporter.CustomErrorReporter'
            }
        },

    .. method:: send_mail(subject, message, *args, **kwargs)

        Sends emails to admin users. To customize this behavior, you can
        subclass the :class:`~django.utils.log.AdminEmailHandler` class and
        override this method.

Filters
-------

Django provides some log filters in addition to those provided by the Python
logging module.

.. class:: CallbackFilter(callback)

    This filter accepts a callback function (which should accept a single
    argument, the record to be logged), and calls it for each record that
    passes through the filter. Handling of that record will not proceed if the
    callback returns False.

    For instance, to filter out :exc:`~django.http.UnreadablePostError`
    (raised when a user cancels an upload) from the admin emails, you would
    create a filter function::

        from django.http import UnreadablePostError

        def skip_unreadable_post(record):
            if record.exc_info:
                exc_type, exc_value = record.exc_info[:2]
                if isinstance(exc_value, UnreadablePostError):
                    return False
            return True

    and then add it to your logging config::

        'filters': {
            'skip_unreadable_posts': {
                '()': 'django.utils.log.CallbackFilter',
                'callback': skip_unreadable_post,
            }
        },
        'handlers': {
            'mail_admins': {
                'level': 'ERROR',
                'filters': ['skip_unreadable_posts'],
                'class': 'django.utils.log.AdminEmailHandler'
            }
        },

.. class:: RequireDebugFalse()

    This filter will only pass on records when settings.DEBUG is False.

    This filter is used as follows in the default :setting:`LOGGING`
    configuration to ensure that the :class:`AdminEmailHandler` only sends
    error emails to admins when :setting:`DEBUG` is ``False``::

        'filters': {
            'require_debug_false': {
                '()': 'django.utils.log.RequireDebugFalse',
            }
        },
        'handlers': {
            'mail_admins': {
                'level': 'ERROR',
                'filters': ['require_debug_false'],
                'class': 'django.utils.log.AdminEmailHandler'
            }
        },

.. class:: RequireDebugTrue()

    This filter is similar to :class:`RequireDebugFalse`, except that records are
    passed only when :setting:`DEBUG` is ``True``.

.. _default-logging-configuration:

Django's default logging configuration
======================================

By default, Django configures the following logging:

When :setting:`DEBUG` is ``True``:

* The ``django`` logger sends messages in the ``django`` hierarchy (except
  ``django.server``) at the ``INFO`` level or higher to the console.

When :setting:`DEBUG` is ``False``:

* The ``django`` logger sends messages in the ``django`` hierarchy (except
  ``django.server``)  with ``ERROR`` or ``CRITICAL`` level to
  :class:`AdminEmailHandler`.

Independent of the value of :setting:`DEBUG`:

* The :ref:`django-server-logger` logger sends messages at the ``INFO`` level
  or higher to the console.

All loggers except :ref:`django-server-logger` propagate logging to their
parents, up to the root ``django`` logger. The ``console`` and ``mail_admins``
handlers are attached to the root logger to provide the behavior described
above.

See also :ref:`Configuring logging <configuring-logging>` to learn how you can
complement or replace this default logging configuration defined in
:source:`django/utils/log.py`.

 </s> add  </s> remove The built-in :class:`AdminEmailHandler` deserves a mention in the context of
security. If its ``include_html`` option is enabled, the email message it sends
will contain a full traceback, with names and values of local variables at each
level of the stack, plus the values of your Django settings (in other words,
the same level of detail that is exposed in a web page when :setting:`DEBUG` is
``True``).
 </s> add The built-in :class:`~django.utils.log.AdminEmailHandler` deserves a mention in
the context of security. If its ``include_html`` option is enabled, the email
message it sends will contain a full traceback, with names and values of local
variables at each level of the stack, plus the values of your Django settings
(in other words, the same level of detail that is exposed in a web page when
:setting:`DEBUG` is ``True``). </s> remove # require_debug_true filter.
 </s> add # require_debug_true filter. This configuration is quoted in
# docs/ref/logging.txt; please amend it there if edited here. </s> remove Django uses Python's builtin :mod:`logging` module to perform system logging.
The usage of this module is discussed in detail in Python's own documentation.
However, if you've never used Python's logging framework (or even if you have),
here's a quick primer.
 </s> add Django uses and extends Python's builtin :mod:`logging` module to perform
system logging. This module is discussed in detail in Python's own
documentation; this section provides a quick overview. </s> remove   * ``mail_admins``, an :class:`AdminEmailHandler`, which emails any ``ERROR``
    (or higher) message to the site :setting:`ADMINS`. This handler uses the
    ``special`` filter.
 </s> add   * ``mail_admins``, an :class:`~django.utils.log.AdminEmailHandler`, which
    emails any ``ERROR`` (or higher) message to the site :setting:`ADMINS`.
    This handler uses the ``special`` filter.
.. _naming-loggers-hierarchy:

Logger hierarchy
~~~~~~~~~~~~~~~~

      # Get an instance of a specific named logger
      logger = logging.getLogger('project.interesting.stuff')
  
.. _naming-loggers-hierarchy:

Logger hierarchy
~~~~~~~~~~~~~~~~

  The dotted paths of logger names define a hierarchy. The
  ``project.interesting`` logger is considered to be a parent of the
  ``project.interesting.stuff`` logger; the ``project`` logger
  is a parent of the ``project.interesting`` logger.
  
keep keep add keep keep keep keep keep
 Refs #32880 -- Moved logging reference to new document.

Completed a first step in moving reference and how-to material out of
the topic document. 
docs/topics/logging.txt