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single default handler and formatter don't remove handlers configure level once using setLevel document logging reorganize logging testspull/2436/head
David Lord
7 years ago
13 changed files with 404 additions and 456 deletions
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.. _logging: |
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Logging |
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======= |
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Flask uses standard Python :mod:`logging`. All Flask-related messages are |
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logged under the ``'flask'`` logger namespace. |
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:meth:`Flask.logger <flask.Flask.logger>` returns the logger named |
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``'flask.app'``, and can be used to log messages for your application. :: |
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@app.route('/login', methods=['POST']) |
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def login(): |
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user = get_user(request.form['username']) |
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if user.check_password(request.form['password']): |
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login_user(user) |
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app.logger.info('%s logged in successfully', user.username) |
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return redirect(url_for('index')) |
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else: |
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app.logger.info('%s failed to log in', user.username) |
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abort(401) |
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Basic Configuration |
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------------------- |
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When you want to configure logging for your project, you should do it as soon |
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as possible when the program starts. If :meth:`app.logger <flask.Flask.logger>` |
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is accessed before logging is configured, it will add a default handler. If |
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possible, configure logging before creating the application object. |
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This example uses :func:`~logging.config.dictConfig` to create a logging |
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configuration similar to Flask's default, except for all logs:: |
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from logging.config import dictConfig |
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dictConfig({ |
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'version': 1, |
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'formatters': {'default': { |
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'format': '[%(asctime)s] %(levelname)s in %(module)s: %(message)s', |
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}}, |
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'handlers': {'wsgi': { |
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'class': 'logging.StreamHandler', |
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'stream': 'ext://flask.logging.wsgi_errors_stream', |
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'formatter': 'default' |
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}}, |
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'root': { |
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'level': 'INFO', |
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'handlers': ['wsgi'] |
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} |
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}) |
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app = Flask(__name__) |
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Default Configuration |
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````````````````````` |
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If you do not configure logging yourself, Flask will add a |
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:class:`~logging.StreamHandler` to :meth:`app.logger <flask.Flask.logger>` |
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automatically. During requests, it will write to the stream specified by the |
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WSGI server in ``environ['wsgi.errors']`` (which is usually |
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:data:`sys.stderr`). Outside a request, it will log to :data:`sys.stderr`. |
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Removing the Default Handler |
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```````````````````````````` |
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If you configured logging after accessing |
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:meth:`app.logger <flask.Flask.logger>`, and need to remove the default |
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handler, you can import and remove it:: |
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from flask.logging import default_handler |
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app.logger.removeHandler(default_handler) |
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Email Errors to Admins |
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---------------------- |
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When running the application on a remote server for production, you probably |
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won't be looking at the log messages very often. The WSGI server will probably |
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send log messages to a file, and you'll only check that file if a user tells |
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you something went wrong. |
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To be proactive about discovering and fixing bugs, you can configure a |
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:class:`logging.handlers.SMTPHandler` to send an email when errors and higher |
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are logged. :: |
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import logging |
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from logging.handlers import SMTPHandler |
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mail_handler = SMTPHandler( |
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mailhost='127.0.0.1', |
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fromaddr='server-error@example.com', |
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toaddrs=['admin@example.com'], |
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subject='Application Error' |
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) |
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mail_handler.setLevel(logging.ERROR) |
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mail_handler.setFormatter(logging.Formatter( |
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'[%(asctime)s] %(levelname)s in %(module)s: %(message)s' |
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)) |
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if not app.debug: |
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app.logger.addHandler(mail_handler) |
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This requires that you have an SMTP server set up on the same server. See the |
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Python docs for more information about configuring the handler. |
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Injecting Request Information |
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----------------------------- |
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Seeing more information about the request, such as the IP address, may help |
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debugging some errors. You can subclass :class:`logging.Formatter` to inject |
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your own fields that can be used in messages. You can change the formatter for |
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Flask's default handler, the mail handler defined above, or any other |
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handler. :: |
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from flask import request |
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from flask.logging import default_handler |
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class RequestFormatter(logging.Formatter): |
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def format(self, record): |
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record.url = request.url |
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record.remote_addr = request.remote_addr |
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return super().format(record) |
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formatter = RequestFormatter( |
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'[%(asctime)s] %(remote_addr)s requested %(url)s\n' |
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'%(levelname)s in %(module)s: %(message)s' |
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)) |
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default_handler.setFormatter(formatter) |
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mail_handler.setFormatter(formatter) |
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Other Libraries |
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--------------- |
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Other libraries may use logging extensively, and you want to see relevant |
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messages from those logs too. The simplest way to do this is to add handlers |
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to the root logger instead of only the app logger. :: |
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from flask.logging import default_handler |
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root = logging.getLogger() |
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root.addHandler(default_handler) |
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root.addHandler(mail_handler) |
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Depending on your project, it may be more useful to configure each logger you |
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care about separately, instead of configuring only the root logger. :: |
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for logger in ( |
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app.logger, |
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logging.getLogger('sqlalchemy'), |
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logging.getLogger('other_package'), |
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): |
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logger.addHandler(default_handler) |
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logger.addHandler(mail_handler) |
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Werkzeug |
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```````` |
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Werkzeug logs basic request/response information to the ``'werkzeug'`` logger. |
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If the root logger has no handlers configured, Werkzeug adds a |
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:class:`~logging.StreamHandler` to its logger. |
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Flask Extensions |
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```````````````` |
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Depending on the situation, an extension may choose to log to |
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:meth:`app.logger <flask.Flask.logger>` or its own named logger. Consult each |
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extension's documentation for details. |
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@ -1,94 +1,69 @@
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# -*- coding: utf-8 -*- |
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""" |
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flask.logging |
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~~~~~~~~~~~~~ |
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Implements the logging support for Flask. |
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:copyright: (c) 2015 by Armin Ronacher. |
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:license: BSD, see LICENSE for more details. |
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""" |
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from __future__ import absolute_import |
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import logging |
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import sys |
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from werkzeug.local import LocalProxy |
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from logging import getLogger, StreamHandler, Formatter, getLoggerClass, \ |
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DEBUG, ERROR |
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from .globals import _request_ctx_stack |
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PROD_LOG_FORMAT = '[%(asctime)s] %(levelname)s in %(module)s: %(message)s' |
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DEBUG_LOG_FORMAT = ( |
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'-' * 80 + '\n' + |
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'%(levelname)s in %(module)s [%(pathname)s:%(lineno)d]:\n' + |
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'%(message)s\n' + |
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'-' * 80 |
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) |
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from .globals import request |
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@LocalProxy |
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def _proxy_stream(): |
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"""Finds the most appropriate error stream for the application. If a |
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WSGI request is in flight we log to wsgi.errors, otherwise this resolves |
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to sys.stderr. |
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def wsgi_errors_stream(): |
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"""Find the most appropriate error stream for the application. If a request |
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is active, log to ``wsgi.errors``, otherwise use ``sys.stderr``. |
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If you configure your own :class:`logging.StreamHandler`, you may want to |
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use this for the stream. If you are using file or dict configuration and |
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can't import this directly, you can refer to it as |
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``ext://flask.logging.wsgi_errors_stream``. |
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""" |
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ctx = _request_ctx_stack.top |
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if ctx is not None: |
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return ctx.request.environ['wsgi.errors'] |
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return sys.stderr |
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return request.environ['wsgi.errors'] if request else sys.stderr |
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def has_level_handler(logger): |
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"""Check if there is a handler in the logging chain that will handle the |
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given logger's :meth:`effective level <~logging.Logger.getEffectiveLevel>`. |
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""" |
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level = logger.getEffectiveLevel() |
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current = logger |
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while current: |
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if any(handler.level <= level for handler in current.handlers): |
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return True |
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if not current.propagate: |
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break |
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current = current.parent |
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def _should_log_for(app, mode): |
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policy = app.config['LOGGER_HANDLER_POLICY'] |
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if policy == mode or policy == 'always': |
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return True |
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return False |
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#: Log messages to :func:`~flask.logging.wsgi_errors_stream` with the format |
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#: ``[%(asctime)s] %(levelname)s in %(module)s: %(message)s``. |
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default_handler = logging.StreamHandler(wsgi_errors_stream) |
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default_handler.setFormatter(logging.Formatter( |
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'[%(asctime)s] %(levelname)s in %(module)s: %(message)s' |
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)) |
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def create_logger(app): |
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"""Creates a logger for the given application. This logger works |
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similar to a regular Python logger but changes the effective logging |
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level based on the application's debug flag. Furthermore this |
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function also removes all attached handlers in case there was a |
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logger with the log name before. |
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"""Get the ``'flask.app'`` logger and configure it if needed. |
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When :attr:`~flask.Flask.debug` is enabled, set the logger level to |
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:data:`logging.DEBUG` if it is not set. |
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If there is no handler for the logger's effective level, add a |
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:class:`~logging.StreamHandler` for |
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:func:`~flask.logging.wsgi_errors_stream` with a basic format. |
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""" |
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Logger = getLoggerClass() |
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class DebugLogger(Logger): |
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def getEffectiveLevel(self): |
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if self.level == 0 and app.debug: |
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return DEBUG |
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return Logger.getEffectiveLevel(self) |
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class DebugHandler(StreamHandler): |
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def emit(self, record): |
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if app.debug and _should_log_for(app, 'debug'): |
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StreamHandler.emit(self, record) |
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class ProductionHandler(StreamHandler): |
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def emit(self, record): |
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if not app.debug and _should_log_for(app, 'production'): |
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StreamHandler.emit(self, record) |
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debug_handler = DebugHandler() |
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debug_handler.setLevel(DEBUG) |
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debug_handler.setFormatter(Formatter(DEBUG_LOG_FORMAT)) |
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prod_handler = ProductionHandler(_proxy_stream) |
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prod_handler.setLevel(ERROR) |
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prod_handler.setFormatter(Formatter(PROD_LOG_FORMAT)) |
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logger = getLogger(app.logger_name) |
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# just in case that was not a new logger, get rid of all the handlers |
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# already attached to it. |
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del logger.handlers[:] |
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logger.__class__ = DebugLogger |
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logger.addHandler(debug_handler) |
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logger.addHandler(prod_handler) |
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# Disable propagation by default |
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logger.propagate = False |
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logger = logging.getLogger('flask.app') |
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if app.debug and logger.level == logging.NOTSET: |
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logger.setLevel(logging.DEBUG) |
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if not has_level_handler(logger): |
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logger.addHandler(default_handler) |
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return logger |
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import logging |
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import sys |
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import pytest |
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from flask._compat import StringIO |
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from flask.logging import default_handler, has_level_handler, \ |
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wsgi_errors_stream |
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@pytest.fixture(autouse=True) |
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def reset_logging(monkeypatch): |
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root_handlers = logging.root.handlers[:] |
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root_level = logging.root.level |
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logger = logging.getLogger('flask.app') |
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logger.handlers = [] |
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logger.setLevel(logging.NOTSET) |
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yield |
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logging.root.handlers[:] = root_handlers |
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logging.root.setLevel(root_level) |
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logger.handlers = [] |
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logger.setLevel(logging.NOTSET) |
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def test_logger(app): |
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assert app.logger.name == 'flask.app' |
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assert app.logger.level == logging.NOTSET |
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assert app.logger.handlers == [default_handler] |
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def test_logger_debug(app): |
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app.debug = True |
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assert app.logger.level == logging.DEBUG |
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assert app.logger.handlers == [default_handler] |
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def test_existing_handler(app): |
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logging.root.addHandler(logging.StreamHandler()) |
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assert app.logger.level == logging.NOTSET |
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assert not app.logger.handlers |
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def test_wsgi_errors_stream(app, client): |
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@app.route('/') |
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def index(): |
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app.logger.error('test') |
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return '' |
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stream = StringIO() |
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client.get('/', errors_stream=stream) |
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assert 'ERROR in test_logging: test' in stream.getvalue() |
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assert wsgi_errors_stream._get_current_object() is sys.stderr |
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with app.test_request_context(errors_stream=stream): |
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assert wsgi_errors_stream._get_current_object() is stream |
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def test_has_level_handler(): |
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logger = logging.getLogger('flask.app') |
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assert not has_level_handler(logger) |
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handler = logging.StreamHandler() |
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logging.root.addHandler(handler) |
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assert has_level_handler(logger) |
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logger.propagate = False |
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assert not has_level_handler(logger) |
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logger.propagate = True |
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handler.setLevel(logging.ERROR) |
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assert not has_level_handler(logger) |
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def test_log_view_exception(app, client): |
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@app.route('/') |
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def index(): |
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raise Exception('test') |
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app.testing = False |
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stream = StringIO() |
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rv = client.get('/', errors_stream=stream) |
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assert rv.status_code == 500 |
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assert rv.data |
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err = stream.getvalue() |
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assert 'Exception on / [GET]' in err |
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assert 'Exception: test' in err |
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