The DevOps Handbook: How to Create World-Class Agility, Reliability, and Security in Technology Organizations

by Gene Kim

To support these various usage models, we have different logging levels, some of which may also trigger alerts, such as the following: DEBUG level: Information at this level is about anything that happens in the program, most often used during debugging. Often, debug logs are disabled in production but temporarily enabled during troubleshooting. INFO level: Information at this level consists of actions that are user-driven or system specific (e.g., “beginning credit card transaction”). WARN level: Information at this level tells us of conditions that could potentially become an error (e.g., a database call taking longer than some predefined time). These will likely initiate an alert and troubleshooting, while other logging messages may help us better understand what led to this condition. ERROR level: Information at this level focuses on error conditions (e.g., API call failures, internal error conditions). FATAL level: Information at this level tells us when we must terminate (e.g., a network daemon can’t bind a network socket).