How to Use Monolog to Write Logs¶
Monolog is a logging library for PHP 5.3 used by Symfony. It is inspired by the Python LogBook library.
Usage¶
To log a message simply get the logger service from the container in your controller:
public function indexAction()
{
$logger = $this->get('logger');
$logger->info('I just got the logger');
$logger->error('An error occurred');
// ...
}
The logger service has different methods for different logging levels. See LoggerInterface for details on which methods are available.
Handlers and Channels: Writing Logs to different Locations¶
In Monolog each logger defines a logging channel, which organizes your log messages into different “categories”. Then, each channel has a stack of handlers to write the logs (the handlers can be shared).
小技巧
When injecting the logger in a service you can use a custom channel control which “channel” the logger will log to.
The basic handler is the StreamHandler which writes logs in a stream (by default in the app/logs/prod.log in the prod environment and app/logs/dev.log in the dev environment).
Monolog comes also with a powerful built-in handler for the logging in prod environment: FingersCrossedHandler. It allows you to store the messages in a buffer and to log them only if a message reaches the action level (error in the configuration provided in the Standard Edition) by forwarding the messages to another handler.
Using several Handlers¶
The logger uses a stack of handlers which are called successively. This allows you to log the messages in several ways easily.
- YAML
# app/config/config.yml monolog: handlers: applog: type: stream path: /var/log/symfony.log level: error main: type: fingers_crossed action_level: warning handler: file file: type: stream level: debug syslog: type: syslog level: error
- XML
<!-- app/config/config.xml --> <?xml version="1.0" encoding="UTF-8" ?> <container xmlns="http://symfony.com/schema/dic/services" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:monolog="http://symfony.com/schema/dic/monolog" xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd http://symfony.com/schema/dic/monolog http://symfony.com/schema/dic/monolog/monolog-1.0.xsd"> <monolog:config> <monolog:handler name="applog" type="stream" path="/var/log/symfony.log" level="error" /> <monolog:handler name="main" type="fingers_crossed" action-level="warning" handler="file" /> <monolog:handler name="file" type="stream" level="debug" /> <monolog:handler name="syslog" type="syslog" level="error" /> </monolog:config> </container>
- PHP
// app/config/config.php $container->loadFromExtension('monolog', array( 'handlers' => array( 'applog' => array( 'type' => 'stream', 'path' => '/var/log/symfony.log', 'level' => 'error', ), 'main' => array( 'type' => 'fingers_crossed', 'action_level' => 'warning', 'handler' => 'file', ), 'file' => array( 'type' => 'stream', 'level' => 'debug', ), 'syslog' => array( 'type' => 'syslog', 'level' => 'error', ), ), ));
The above configuration defines a stack of handlers which will be called in the order they are defined.
小技巧
The handler named “file” will not be included in the stack itself as it is used as a nested handler of the fingers_crossed handler.
注解
If you want to change the config of MonologBundle in another config file you need to redefine the whole stack. It cannot be merged because the order matters and a merge does not allow to control the order.
Changing the Formatter¶
The handler uses a Formatter to format the record before logging it. All Monolog handlers use an instance of Monolog\Formatter\LineFormatter by default but you can replace it easily. Your formatter must implement Monolog\Formatter\FormatterInterface.
- YAML
# app/config/config.yml services: my_formatter: class: Monolog\Formatter\JsonFormatter monolog: handlers: file: type: stream level: debug formatter: my_formatter
- XML
<!-- app/config/config.xml --> <?xml version="1.0" encoding="UTF-8" ?> <container xmlns="http://symfony.com/schema/dic/services" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:monolog="http://symfony.com/schema/dic/monolog" xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd http://symfony.com/schema/dic/monolog http://symfony.com/schema/dic/monolog/monolog-1.0.xsd"> <services> <service id="my_formatter" class="Monolog\Formatter\JsonFormatter" /> </services> <monolog:config> <monolog:handler name="file" type="stream" level="debug" formatter="my_formatter" /> </monolog:config> </container>
- PHP
// app/config/config.php $container ->register('my_formatter', 'Monolog\Formatter\JsonFormatter'); $container->loadFromExtension('monolog', array( 'handlers' => array( 'file' => array( 'type' => 'stream', 'level' => 'debug', 'formatter' => 'my_formatter', ), ), ));
Adding some extra Data in the Log Messages¶
Monolog allows you to process the record before logging it to add some extra data. A processor can be applied for the whole handler stack or only for a specific handler.
A processor is simply a callable receiving the record as its first argument.
Processors are configured using the monolog.processor DIC tag. See the reference about it.
Adding a Session/Request Token¶
Sometimes it is hard to tell which entries in the log belong to which session and/or request. The following example will add a unique token for each request using a processor.
namespace Acme\MyBundle;
use Symfony\Component\HttpFoundation\Session\Session;
class SessionRequestProcessor
{
private $session;
private $token;
public function __construct(Session $session)
{
$this->session = $session;
}
public function processRecord(array $record)
{
if (null === $this->token) {
try {
$this->token = substr($this->session->getId(), 0, 8);
} catch (\RuntimeException $e) {
$this->token = '????????';
}
$this->token .= '-' . substr(uniqid(), -8);
}
$record['extra']['token'] = $this->token;
return $record;
}
}
- YAML
# app/config/config.yml services: monolog.formatter.session_request: class: Monolog\Formatter\LineFormatter arguments: - "[%%datetime%%] [%%extra.token%%] %%channel%%.%%level_name%%: %%message%%\n" monolog.processor.session_request: class: Acme\MyBundle\SessionRequestProcessor arguments: ["@session"] tags: - { name: monolog.processor, method: processRecord } monolog: handlers: main: type: stream path: "%kernel.logs_dir%/%kernel.environment%.log" level: debug formatter: monolog.formatter.session_request
- XML
<!-- app/config/config.xml --> <?xml version="1.0" encoding="UTF-8" ?> <container xmlns="http://symfony.com/schema/dic/services" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:monolog="http://symfony.com/schema/dic/monolog" xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd http://symfony.com/schema/dic/monolog http://symfony.com/schema/dic/monolog/monolog-1.0.xsd"> <services> <service id="monolog.formatter.session_request" class="Monolog\Formatter\LineFormatter"> <argument>[%%datetime%%] [%%extra.token%%] %%channel%%.%%level_name%%: %%message%%
</argument> </service> <service id="monolog.processor.session_request" class="Acme\MyBundle\SessionRequestProcessor"> <argument type="service" id="session" /> <tag name="monolog.processor" method="processRecord" /> </service> </services> <monolog:config> <monolog:handler name="main" type="stream" path="%kernel.logs_dir%/%kernel.environment%.log" level="debug" formatter="monolog.formatter.session_request" /> </monolog:config> </container>
- PHP
// app/config/config.php $container ->register( 'monolog.formatter.session_request', 'Monolog\Formatter\LineFormatter' ) ->addArgument('[%%datetime%%] [%%extra.token%%] %%channel%%.%%level_name%%: %%message%%\n'); $container ->register( 'monolog.processor.session_request', 'Acme\MyBundle\SessionRequestProcessor' ) ->addArgument(new Reference('session')) ->addTag('monolog.processor', array('method' => 'processRecord')); $container->loadFromExtension('monolog', array( 'handlers' => array( 'main' => array( 'type' => 'stream', 'path' => '%kernel.logs_dir%/%kernel.environment%.log', 'level' => 'debug', 'formatter' => 'monolog.formatter.session_request', ), ), ));
注解
If you use several handlers, you can also register a processor at the handler level or at the channel level instead of registering it globally (see the following sections).
Registering Processors per Handler¶
You can register a processor per handler using the handler option of the monolog.processor tag:
- YAML
# app/config/config.yml services: monolog.processor.session_request: class: Acme\MyBundle\SessionRequestProcessor arguments: ["@session"] tags: - { name: monolog.processor, method: processRecord, handler: main }
- XML
<!-- app/config/config.xml --> <?xml version="1.0" encoding="UTF-8" ?> <container xmlns="http://symfony.com/schema/dic/services" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:monolog="http://symfony.com/schema/dic/monolog" xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd http://symfony.com/schema/dic/monolog http://symfony.com/schema/dic/monolog/monolog-1.0.xsd"> <services> <service id="monolog.processor.session_request" class="Acme\MyBundle\SessionRequestProcessor"> <argument type="service" id="session" /> <tag name="monolog.processor" method="processRecord" handler="main" /> </service> </services> </container>
- PHP
// app/config/config.php $container ->register( 'monolog.processor.session_request', 'Acme\MyBundle\SessionRequestProcessor' ) ->addArgument(new Reference('session')) ->addTag('monolog.processor', array('method' => 'processRecord', 'handler' => 'main'));
Registering Processors per Channel¶
You can register a processor per channel using the channel option of the monolog.processor tag:
- YAML
# app/config/config.yml services: monolog.processor.session_request: class: Acme\MyBundle\SessionRequestProcessor arguments: ["@session"] tags: - { name: monolog.processor, method: processRecord, channel: main }
- XML
<!-- app/config/config.xml --> <?xml version="1.0" encoding="UTF-8" ?> <container xmlns="http://symfony.com/schema/dic/services" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:monolog="http://symfony.com/schema/dic/monolog" xsi:schemaLocation="http://symfony.com/schema/dic/services http://symfony.com/schema/dic/services/services-1.0.xsd http://symfony.com/schema/dic/monolog http://symfony.com/schema/dic/monolog/monolog-1.0.xsd"> <services> <service id="monolog.processor.session_request" class="Acme\MyBundle\SessionRequestProcessor"> <argument type="service" id="session" /> <tag name="monolog.processor" method="processRecord" channel="main" /> </service> </services> </container>
- PHP
// app/config/config.php $container ->register( 'monolog.processor.session_request', 'Acme\MyBundle\SessionRequestProcessor' ) ->addArgument(new Reference('session')) ->addTag('monolog.processor', array('method' => 'processRecord', 'channel' => 'main'));