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Logging

.. currentmodule:: aiohttp

aiohttp uses standard :mod:`logging` for tracking the library activity.

We have the following loggers enumerated by names:

  • 'aiohttp.access'
  • 'aiohttp.client'
  • 'aiohttp.internal'
  • 'aiohttp.server'
  • 'aiohttp.web'
  • 'aiohttp.websocket'

You may subscribe to these loggers for getting logging messages. The page does not provide instructions for logging subscribing while the most friendly method is :func:`logging.config.dictConfig` for configuring whole loggers in your application.

Logging does not work out of the box. It requires at least minimal 'logging' configuration. Example of minimal working logger setup:

import logging
from aiohttp import web

app = web.Application()
logging.basicConfig(level=logging.DEBUG)
web.run_app(app, port=5000)

.. versionadded:: 4.0.0

Access logs

Access logs are enabled by default. If the debug flag is set, and the default logger 'aiohttp.access' is used, access logs will be output to :obj:`~sys.stderr` if no handlers are attached. Furthermore, if the default logger has no log level set, the log level will be set to :obj:`logging.DEBUG`.

This logging may be controlled by :meth:`aiohttp.web.AppRunner` and :func:`aiohttp.web.run_app`.

To override the default logger, pass an instance of :class:`logging.Logger` to override the default logger.

Note

Use web.run_app(app, access_log=None) to disable access logs.

In addition, access_log_format may be used to specify the log format.

Format specification

The library provides custom micro-language to specifying info about request and response:

Option Meaning
%% The percent sign
%a Remote IP-address (IP-address of proxy if using reverse proxy)
%t Time when the request was started to process
%P The process ID of the child that serviced the request
%r First line of request
%s Response status code
%b Size of response in bytes, including HTTP headers
%T The time taken to serve the request, in seconds
%Tf The time taken to serve the request, in seconds with fraction in %.06f format
%D The time taken to serve the request, in microseconds
%{FOO}i request.headers['FOO']
%{FOO}o response.headers['FOO']

The default access log format is:

'%a %t "%r" %s %b "%{Referer}i" "%{User-Agent}i"'

.. versionadded:: 2.3.0

access_log_class introduced.

Example of a drop-in replacement for the default access logger:

from aiohttp.abc import AbstractAccessLogger

class AccessLogger(AbstractAccessLogger):

    def log(self, request, response, time):
        self.logger.info(f'{request.remote} '
                         f'"{request.method} {request.path} '
                         f'done in {time}s: {response.status}')

Gunicorn access logs

When Gunicorn is used for :ref:`deployment <aiohttp-deployment-gunicorn>`, its default access log format will be automatically replaced with the default aiohttp's access log format.

If Gunicorn's option access_logformat is specified explicitly, it should use aiohttp's format specification.

Gunicorn's access log works only if accesslog is specified explicitly in your config or as a command line option. This configuration can be either a path or '-'. If the application uses a custom logging setup intercepting the 'gunicorn.access' logger, accesslog should be set to '-' to prevent Gunicorn to create an empty access log file upon every startup.

Error logs

:mod:`aiohttp.web` uses a logger named 'aiohttp.server' to store errors given on web requests handling.

This log is enabled by default.

To use a different logger name, pass logger (:class:`logging.Logger` instance) to the :meth:`aiohttp.web.AppRunner` constructor.