# The MongoDB\Driver\Monitoring\LogSubscriber interface

&reftitle.intro;

Classes implementing this interface may be registered as a subscriber and receive log messages from the extension. This is similar to stream-based debug logging (i.e. mongodb.debug) except that trace-level log messages are not received.

As with stream-based logging, it is only possible to register a logger globally using `MongoDB\Driver\Monitoring\addSubscriber`. The extension is not able to distinguish log messages for individual `MongoDB\Driver\Manager` objects.

&reftitle.interfacesynopsis;

        MongoDB\Driver\Monitoring\LogSubscriber

          MongoDB\Driver\Monitoring\LogSubscriber

          MongoDB\Driver\Monitoring\Subscriber

        &Constants;

         const
         int
         MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_ERROR
         0

         const
         int
         MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_CRITICAL
         1

         const
         int
         MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_WARNING
         2

         const
         int
         MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_MESSAGE
         3

         const
         int
         MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_INFO
         4

         const
         int
         MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_DEBUG
         5

        &Methods;

&reftitle.constants;

`MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_ERROR`

- Error log level. An error condition that the extension is unable to report through its API. This is the most severe log level in the extension.

`MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_CRITICAL`

- Critical log level. An error condition with slightly less severity. This constant exists for consistency with libmongoc; however, the extension is unlikely to use it in practice.

`MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_WARNING`

- Warning log level. Indicates a situation where undesirable application behavior may occur.

`MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_MESSAGE`

- Message or notice log level. Indicates an event that is unusual but not problematic.

`MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_INFO`

- Info log level. High-level information about normal driver behavior.

`MongoDB\Driver\Monitoring\LogSubscriber::LEVEL_DEBUG`

- Debug log level. Detailed information that may be helpful when debugging an application.

&reference.mongodb.mongodb.driver.monitoring.entities.logsubscriber;