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Minimalist default PSR-3 logger #10321

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Minimalist default PSR-3 logger
dunglas Sep 10, 2018
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dunglas Sep 10, 2018
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dunglas Sep 10, 2018
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dunglas Sep 10, 2018
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51 changes: 42 additions & 9 deletions logging.rst
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@@ -1,14 +1,29 @@
Logging with Monolog
====================
Logging
=======

Symfony comes with an outside library - called Monolog_ - that allows you to create
logs that can be stored in a variety of different places.
Symfony comes with a minimalist `PSR-3`_ logger: :class:`Symfony\\Component\\HttpKernel\\Log\\Logger`.
In conformance with `the twelve-factor app methodology`_, it sends messages starting from the
``WARNING`` level to `stderr`_.

The minimal log level can be changed by setting the ``SHELL_VERBOSITY`` environment variable:

========================= =================
``SHELL_VERBOSITY`` value Minimum log level
========================= =================
``-1`` ``ERROR``
``1`` ``NOTICE``
``2`` ``INFO``
``3`` ``DEBUG``
========================= =================

The minimum log level, the default output and the log format can also be changed by
passing the appropriate arguments to the constructor of :class:`Symfony\\Component\\HttpKernel\\Log\\Logger`.
To do so, :ref:`override the "logger" service definition <service-psr4-loader>`.

Logging a Message
-----------------

To log a message, fetch the ``logger`` service from the container in
your controller::
To log a message, inject the default logger in your controller::

use Psr\Log\LoggerInterface;

Expand All @@ -29,11 +44,26 @@ your controller::
}

The ``logger`` service has different methods for different logging levels/priorities.
You can configure the logger to do different things based on the *level* of a message
(e.g. :doc:`send an email when an error occurs </logging/monolog_email>`).

See LoggerInterface_ for a list of all of the methods on the logger.

Monolog
-------

Symfony integrates seamlessly with `Monolog`_, the most popular PHP logging
library, to create and store log messages in a variety of different places
and trigger various actions.

For instance, using Monolog you can configure the logger to do different things based on the
*level* of a message (e.g. :doc:`send an email when an error occurs </logging/monolog_email>`).

Run this command to install the Monolog based logger before using it:

.. code-block:: terminal

$ composer require symfony/monolog-bundle

The following sections assume that Monolog is installed.

Where Logs are Stored
---------------------

Expand Down Expand Up @@ -338,6 +368,9 @@ Learn more

logging/*

.. _`the twelve-factor app methodology`: https://12factor.net/logs
.. _PSR-3: https://www.php-fig.org/psr/psr-3/
.. _`stderr`: https://en.wikipedia.org/wiki/Standard_streams#Standard_error_(stderr)
.. _Monolog: https://github.com/Seldaek/monolog
.. _LoggerInterface: https://github.com/php-fig/log/blob/master/Psr/Log/LoggerInterface.php
.. _`logrotate`: https://github.com/logrotate/logrotate
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