ロギング¶

登場人物¶

Pythonのロギングは4つの部分で構成されます。

• ロガー
• ハンドラ
• フィルタ
• フォーマッタ

ロガーに名前をつける¶

The call to logging.getLogger() obtains (creating, if necessary) an instance of a logger. The logger instance is identified by a name. This name is used to identify the logger for configuration purposes.

慣習として、logger の名前は通常 __name__ とし、logger が含まれている Python モジュールの名前となるようにします。これにより、ロギングの呼び出しをモジュールごとにフィルタ・ハンドリングできるようになります。しかし、ロギングメッセージを他の方法で組織したい場合は、ドット区切りの名前を logger に与えることもできます。

# 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.

Why is the hierarchy important? Well, because loggers can be set to propagate their logging calls to their parents. In this way, you can define a single set of handlers at the root of a logger tree, and capture all logging calls in the subtree of loggers. A logger defined in the project namespace will catch all logging messages issued on the project.interesting and project.interesting.stuff loggers.

This propagation can be controlled on a per-logger basis. If you don't want a particular logger to propagate to its parents, you can turn off this behavior.

ロギング呼び出しを作成する¶

ロガーのインスタンスは、デフォルトの各ログレベルに対する入力方法を含んでいます:

• logger.debug()
• logger.info()
• logger.warning()
• logger.error()
• logger.critical()

さらに 2 つのロギング呼び出しが可能です:

• logger.log(): 手動で、特定のログレベルでロギングメッセージを吐き出します。
• logger.exception(): Creates an ERROR level logging message wrapping the current exception stack frame.

例¶

dictConfig フォーマット に関する完全なドキュメントが、ロギング設定ディクショナリの最高の教材です。とはいえ、どんなことが可能なのか知ってもらうため、以下にいくつかの例を示します。

To begin, here's a small configuration that will allow you to output all log messages to the console:

import os

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
        },
    },
    'root': {
        'handlers': ['console'],
        'level': 'WARNING',
    },
}

This configures the parent root logger to send messages with the WARNING level and higher to the console handler. By adjusting the level to INFO or DEBUG you can display more messages. This may be useful during development.

Next we can add more fine-grained logging. Here's an example of how to make the logging system print more messages from just the django named logger:

import os

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'console': {
            'class': 'logging.StreamHandler',
        },
    },
    'root': {
        'handlers': ['console'],
        'level': 'WARNING',
    },
    'loggers': {
        'django': {
            'handlers': ['console'],
            'level': os.getenv('DJANGO_LOG_LEVEL', 'INFO'),
            'propagate': False,
        },
    },
}

By default, this config sends messages from the django logger of level INFO or higher to the console. This is the same level as Django's default logging config, except that the default config only displays log records when DEBUG=True. Django does not log many such INFO level messages. With this config, however, you can also set the environment variable DJANGO_LOG_LEVEL=DEBUG to see all of Django's debug logging which is very verbose as it includes all database queries.

You don't have to log to the console. Here's a configuration which writes all logging from the django named logger to a local file:

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'handlers': {
        'file': {
            'level': 'DEBUG',
            'class': 'logging.FileHandler',
            'filename': '/path/to/django/debug.log',
        },
    },
    'loggers': {
        'django': {
            'handlers': ['file'],
            'level': 'DEBUG',
            'propagate': True,
        },
    },
}

この例を使用するときは、'filename' のパスを Django アプリケーションを実行しているユーザーが書き込み可能な場所に変更してください。

Finally, here's an example of a fairly complex logging setup:

LOGGING = {
    'version': 1,
    'disable_existing_loggers': False,
    'formatters': {
        'verbose': {
            'format': '{levelname} {asctime} {module} {process:d} {thread:d} {message}',
            'style': '{',
        },
        'simple': {
            'format': '{levelname} {message}',
            'style': '{',
        },
    },
    'filters': {
        'special': {
            '()': 'project.logging.SpecialFilter',
            'foo': 'bar',
        },
        'require_debug_true': {
            '()': 'django.utils.log.RequireDebugTrue',
        },
    },
    'handlers': {
        'console': {
            'level': 'INFO',
            'filters': ['require_debug_true'],
            'class': 'logging.StreamHandler',
            'formatter': 'simple'
        },
        'mail_admins': {
            'level': 'ERROR',
            'class': 'django.utils.log.AdminEmailHandler',
            'filters': ['special']
        }
    },
    'loggers': {
        'django': {
            'handlers': ['console'],
            'propagate': True,
        },
        'django.request': {
            'handlers': ['mail_admins'],
            'level': 'ERROR',
            'propagate': False,
        },
        'myproject.custom': {
            'handlers': ['console', 'mail_admins'],
            'level': 'INFO',
            'filters': ['special']
        }
    }
}

このロギング設定は、以下のことを行います:

• 設定が「dictConfig バージョン 1」形式であることを明示します。 現在、これが唯一の dictConfig 形式のバージョンです。

• 2 つのフォーマッタを定義します:

  • simple, that outputs the log level name (e.g., DEBUG) and the log message.

    この format 文字列は標準の Python 文字列フォーマットで、各ログ行で出力される詳細を定義します。出力可能な詳細の全リストは Formatter Objects に記載されています。

  • verbose は、ログレベルの名称とログメッセージに加えて、時刻、プロセス、スレッド、ログメッセージを生成したモジュールを出力します。

• 2 つのフィルタを定義します:

  • project.logging.SpecialFilter, using the alias special. If this filter required additional arguments, they can be provided as additional keys in the filter configuration dictionary. In this case, the argument foo will be given a value of bar when instantiating SpecialFilter.
  • django.utils.log.RequireDebugTrue は、DEBUG が True のときにレコードの処理を進めます。

• 2 つのハンドラを定義します:

  • console は、すべての INFO 以上のメッセージを sys.stderr に表示 (print) する StreamHandler クラスです。このハンドラは simple 出力フォーマットを使用します。
  • mail_admins` は、すべての ``ERROR 以上のメッセージを ADMINS に E メール送信する AdminEmailHandler です。このハンドラは special フィルタを使用します。

• 3 つのロガーを設定します:

  • django は、すべてのメッセージを console ハンドラに渡します。
  • django.request は、すべての ERROR メッセージを mail_admins ハンドラに渡します。加えて、このロガーはメッセージを親に 伝えない よう設定されています。これは、django.request 内に記述されたログメッセージは django ロガーで処理されないことを意味します。
  • myproject.custom は INFO もしくはそれ以上のすべてのメッセージを渡し、special フィルタを 2 つのハンドラに引き渡します -- console と mail_admins です。これは、INFO 以上のレベルのメッセージがコンソールで表示され、さらに ERROR と CRITICAL のメッセージは E メールでも出力されることを意味します。

カスタムのロギング設定¶

ロガーの設定に Python の dictConfig フォーマットを使用したくない場合は、あなた自身の設定スキームを定義することができます。

The LOGGING_CONFIG setting defines the callable that will be used to configure Django's loggers. By default, it points at Python's logging.config.dictConfig() function. However, if you want to use a different configuration process, you can use any other callable that takes a single argument. The contents of LOGGING will be provided as the value of that argument when logging is configured.

ロギング設定を無効化する¶

If you don't want to configure logging at all (or you want to manually configure logging using your own approach), you can set LOGGING_CONFIG to None. This will disable the configuration process for Django's default logging.

Setting LOGGING_CONFIG to None only means that the automatic configuration process is disabled, not logging itself. If you disable the configuration process, Django will still make logging calls, falling back to whatever default logging behavior is defined.

Here's an example that disables Django's logging configuration and then manually configures logging:

LOGGING_CONFIG = None

import logging.config
logging.config.dictConfig(...)

Note that the default configuration process only calls LOGGING_CONFIG once settings are fully-loaded. In contrast, manually configuring the logging in your settings file will load your logging config immediately. As such, your logging config must appear after any settings on which it depends.

ロガー¶

Django provides several built-in loggers.

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

ハンドラ¶

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 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 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 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,
    }
},

Note that this HTML version of the email contains a full traceback, with names and values of local variables at each level of the stack, plus the values of your Django settings. This information is potentially very sensitive, and you may not want to send it over email. Consider using something such as Sentry to get the best of both worlds -- the rich information of full tracebacks plus the security of not sending the information over email. You may also explicitly designate certain sensitive information to be filtered out of error reports -- learn more on Filtering error reports.

By setting the email_backend argument of AdminEmailHandler, the email backend 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 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'
    }
},

New in Django 3.0:

The reporter_class argument was added.

send_mail(subject, message, *args, **kwargs)¶

Sends emails to admin users. To customize this behavior, you can subclass the AdminEmailHandler class and override this method.

フィルタ¶

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 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 LOGGING configuration to ensure that the AdminEmailHandler only sends error emails to admins when 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 RequireDebugFalse, except that records are passed only when DEBUG is True.