How to Configure Monolog to Email Errors

How to Configure Monolog to Email Errors

Monolog can be configured to send an email when an error occurs with an application. The configuration for this requires a few nested handlers in order to avoid receiving too many emails. This configuration looks complicated at first but each handler is fairly straight forward when it is broken down.

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    # app/config/config_prod.yml
    monolog:
        handlers:
            mail:
                type:         fingers_crossed
                action_level: critical
                handler:      buffered
            buffered:
                type:    buffer
                handler: swift
            swift:
                type:       swift_mailer
                from_email: error@example.com
                to_email:   error@example.com
                # or list of recipients
                # to_email:   [dev1@example.com, dev2@example.com, ...]
                subject:    An Error Occurred!
                level:      debug
    
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    <!-- app/config/config_prod.xml -->
    <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="mail"
                type="fingers_crossed"
                action-level="critical"
                handler="buffered"
            />
            <monolog:handler
                name="buffered"
                type="buffer"
                handler="swift"
            />
            <monolog:handler
                name="swift"
                type="swift_mailer"
                from-email="error@example.com"
                to-email="error@example.com"
                subject="An Error Occurred!"
                level="debug"
            />
        </monolog:config>
    </container>
    
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    // app/config/config_prod.php
    $container->loadFromExtension('monolog', array(
        'handlers' => array(
            'mail' => array(
                'type'         => 'fingers_crossed',
                'action_level' => 'critical',
                'handler'      => 'buffered',
            ),
            'buffered' => array(
                'type'    => 'buffer',
                'handler' => 'swift',
            ),
            'swift' => array(
                'type'       => 'swift_mailer',
                'from_email' => 'error@example.com',
                'to_email'   => 'error@example.com',
                // or a list of recipients
                // 'to_email'   => array('dev1@example.com', 'dev2@example.com', ...),
                'subject'    => 'An Error Occurred!',
                'level'      => 'debug',
            ),
        ),
    ));
    

The mail handler is a fingers_crossed handler which means that it is only triggered when the action level, in this case critical is reached. It then logs everything including messages below the action level. The critical level is only triggered for 5xx HTTP code errors. The handler setting means that the output is then passed onto the buffered handler.

Tip

If you want both 400 level and 500 level errors to trigger an email, set the action_level to error instead of critical.

The buffered handler simply keeps all the messages for a request and then passes them onto the nested handler in one go. If you do not use this handler then each message will be emailed separately. This is then passed to the swift handler. This is the handler that actually deals with emailing you the error. The settings for this are straightforward, the to and from addresses and the subject.

You can combine these handlers with other handlers so that the errors still get logged on the server as well as the emails being sent:

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    # app/config/config_prod.yml
    monolog:
        handlers:
            main:
                type:         fingers_crossed
                action_level: critical
                handler:      grouped
            grouped:
                type:    group
                members: [streamed, buffered]
            streamed:
                type:  stream
                path:  "%kernel.logs_dir%/%kernel.environment%.log"
                level: debug
            buffered:
                type:    buffer
                handler: swift
            swift:
                type:       swift_mailer
                from_email: error@example.com
                to_email:   error@example.com
                subject:    An Error Occurred!
                level:      debug
    
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    <!-- app/config/config_prod.xml -->
    <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="main"
                type="fingers_crossed"
                action_level="critical"
                handler="grouped"
            />
            <monolog:handler
                name="grouped"
                type="group"
            >
                <member type="stream"/>
                <member type="buffered"/>
            </monolog:handler>
            <monolog:handler
                name="stream"
                path="%kernel.logs_dir%/%kernel.environment%.log"
                level="debug"
            />
            <monolog:handler
                name="buffered"
                type="buffer"
                handler="swift"
            />
            <monolog:handler
                name="swift"
                from-email="error@example.com"
                to-email="error@example.com"
                subject="An Error Occurred!"
                level="debug"
            />
        </monolog:config>
    </container>
    
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    // app/config/config_prod.php
    $container->loadFromExtension('monolog', array(
        'handlers' => array(
            'main' => array(
                'type'         => 'fingers_crossed',
                'action_level' => 'critical',
                'handler'      => 'grouped',
            ),
            'grouped' => array(
                'type'    => 'group',
                'members' => array('streamed', 'buffered'),
            ),
            'streamed'  => array(
                'type'  => 'stream',
                'path'  => '%kernel.logs_dir%/%kernel.environment%.log',
                'level' => 'debug',
            ),
            'buffered'    => array(
                'type'    => 'buffer',
                'handler' => 'swift',
            ),
            'swift' => array(
                'type'       => 'swift_mailer',
                'from_email' => 'error@example.com',
                'to_email'   => 'error@example.com',
                'subject'    => 'An Error Occurred!',
                'level'      => 'debug',
            ),
        ),
    ));
    

This uses the group handler to send the messages to the two group members, the buffered and the stream handlers. The messages will now be both written to the log file and emailed.

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