Backstage: Custom RootLogger Ignores Log Level Matchers

Introduction

Hey guys! Today, we're diving deep into a quirky issue within Backstage involving the custom rootLogger factory and its tendency to ignore configured log level matchers. If you've ever scratched your head wondering why your carefully set log levels in app-config.yaml aren't playing nice with your custom logger, you're in the right place. Let's break it down, explore the problem, and see what makes this happen. Understanding rootLogger configuration is critical for effective Backstage deployments, especially when dealing with custom implementations. The primary goal here is to ensure that log levels defined through matchers in app-config.yaml are respected, even when a custom rootLoggerFactory is in use. This ensures consistent and predictable logging behavior across all modules and plugins within your Backstage application.

Configuring the rootLogger in Backstage allows developers to set default logging levels and define overrides for specific modules or patterns. This is particularly useful for debugging and monitoring different parts of the application. When a custom rootLoggerFactory is implemented, it's expected that this factory respects the global logging configurations, including the matchers defined in app-config.yaml. However, as the issue describes, this is not always the case. This discrepancy can lead to confusion and make it harder to diagnose issues because log levels are not behaving as expected. The importance of consistent logging cannot be overstated. Logging is essential for monitoring application health, debugging issues, and ensuring that you have a clear understanding of how your application is behaving in different environments. When custom loggers ignore global configurations, it introduces inconsistencies that can undermine the entire logging strategy. For instance, if you've set a specific plugin to log at a debug level to capture detailed information during troubleshooting, but the custom logger defaults to info and ignores the debug setting, you'll miss critical data. Addressing this issue ensures that developers can rely on their logging configurations to provide the necessary insights for maintaining a healthy and stable Backstage application.

To effectively tackle this problem, it’s essential to have a solid understanding of how Backstage handles logging and how custom loggers are integrated into the system. This knowledge will help in identifying the root cause of the issue and implementing a solution that ensures consistent logging behavior across all components. Understanding the interaction between the rootLoggerFactory, the app-config.yaml configurations, and the underlying logging framework (like Winston) is crucial. By ensuring that custom loggers respect the global logging configurations, you can maintain a reliable and consistent logging strategy that supports effective debugging and monitoring of your Backstage application.

The Problem: Mismatch Between Custom Logger and Configuration

The core issue revolves around a compatibility gap. When you configure a custom rootLoggerFactory in Backstage, the newer log level matchers in the root logger configuration are, unfortunately, ignored. This means any module-specific or pattern-based log level overrides you've meticulously defined in your app-config.yaml simply don't kick in. It's like setting up a fancy sprinkler system only to find out it's not connected to the water main. This is a compatibility issue where the older extensibility mechanism (rootLoggerFactory) doesn't quite jive with the newer matcher-based log level configuration. Essentially, the custom logger you've created isn't picking up the instructions from your configuration file, leading to unexpected logging behavior. The impact of this issue is significant. Developers rely on logging configurations to provide insights into application behavior, diagnose issues, and monitor performance. When log levels are not correctly applied, it can lead to:

• Difficulty in Debugging: Incorrect log levels can hide important information, making it harder to identify and fix bugs.
• Inconsistent Monitoring: If different parts of the application log at different levels than expected, it can skew monitoring data and make it harder to get an accurate picture of application health.
• Configuration Confusion: Developers may spend unnecessary time troubleshooting why their log level configurations are not working as expected.

To fully grasp the problem, let's consider a scenario where you've configured a specific plugin to log at the debug level to capture detailed information during troubleshooting. However, because the custom rootLoggerFactory ignores the log level matchers, the plugin continues to log at the default info level. This means you're missing critical data that could help you diagnose the issue. Similarly, if you've set up different log levels for various modules based on their criticality, a custom logger that ignores these settings can undermine your entire logging strategy. This discrepancy highlights the importance of ensuring compatibility between custom loggers and the global logging configurations. A robust solution should ensure that custom loggers respect the log level matchers defined in app-config.yaml, providing consistent and predictable logging behavior across all components of the Backstage application. By addressing this issue, developers can rely on their logging configurations to provide the necessary insights for maintaining a healthy and stable application.

Expected Behavior: Harmony Between Logger and Configuration

Ideally, your custom rootLoggerFactory implementations should respect the configured log level matchers found in your app-config.yaml. Think of it as your custom logger politely listening to the instructions you've laid out for it. The matcher configuration should apply universally to all loggers created by the factory, ensuring a consistent logging experience regardless of how you've customized things. This means that whether you're using the default logger or a custom one, the log levels should behave as you've defined them in your configuration. In a perfect world, the expected behavior would be seamless integration between custom loggers and the global logging configurations. This would mean that:

• The custom rootLoggerFactory respects the log level matchers defined in app-config.yaml.
• Log levels are applied consistently across all modules and plugins, regardless of whether they are using the default logger or a custom one.
• Developers can rely on their logging configurations to provide accurate and reliable insights into application behavior.

To achieve this, the custom logger needs to be aware of and properly implement the logic for applying log level matchers. This might involve modifying the custom logger factory to read the log level configurations from app-config.yaml and apply them to the loggers it creates. Alternatively, Backstage could provide a mechanism for automatically applying log level matchers to custom loggers, ensuring that they adhere to the global logging configurations. The key is to ensure that custom loggers are not isolated from the rest of the application. They should be integrated into the logging framework in a way that allows them to participate in the global logging strategy. This requires a clear understanding of how Backstage handles logging and how custom loggers are intended to interact with the system. By ensuring that custom loggers respect the global logging configurations, developers can maintain a reliable and consistent logging strategy that supports effective debugging and monitoring of their Backstage application. This not only simplifies troubleshooting but also ensures that the logging data accurately reflects the behavior of the application, leading to better insights and more informed decision-making.

Steps to Reproduce: Seeing is Believing

Let's get our hands dirty and reproduce this issue. Follow these steps:

1. Define a Custom Logger Factory:

   • In packages/backend/src/index.ts, whip up a custom root logger factory. Use the guidelines from Backstage's documentation. For example:

   const loggerFactory = (options: RootLoggerServiceFactoryOptions) => {
     return winston.createLogger({
       level: 'info',
       transports: [new winston.transports.Console()],
     });
   };
   

2. Configure Log Level Matchers:

   • In your app-config.yaml, set up some log level matchers:

   logging:
     rootLogger:
       level: info
       levels:
         - matcher: 'plugin:catalog'
           level: debug
   

3. Start the Backend:

   • Fire up your Backstage backend.

4. Check the Logs:

   • Observe the logs from the catalog plugin. You'll notice they stubbornly remain at the info level instead of the expected debug level.

By following these steps, you can clearly demonstrate the issue and confirm that the custom rootLoggerFactory is indeed ignoring the log level matchers. This hands-on approach is invaluable for understanding the problem and developing potential solutions. The ability to reproduce the issue consistently allows you to test different approaches and verify that they are effective. It also provides a clear and concise way to communicate the problem to other developers and stakeholders. When reporting issues, providing clear and reproducible steps is essential for facilitating collaboration and ensuring that the problem is addressed promptly. In this case, the steps outlined above provide a straightforward way to demonstrate the discrepancy between the expected and actual logging behavior, making it easier to diagnose and resolve the underlying cause. This not only saves time and effort but also ensures that the fix is targeted and effective, leading to a more stable and reliable Backstage application. Remember, reproducibility is key to effective troubleshooting and problem-solving.

Contributing and Collaboration

The reporter of this issue has stated that they are unable to submit a PR, but they are happy to collaborate on a PR with someone else.

Conclusion

So, there you have it! A deep dive into the curious case of the custom rootLogger factory ignoring log level matchers in Backstage. Understanding this issue is crucial for maintaining a healthy and debuggable Backstage application. By ensuring that custom loggers respect the global logging configurations, you can maintain a reliable and consistent logging strategy that supports effective debugging and monitoring. Keep an eye out for updates and fixes, and happy coding, folks! For further reading on Backstage logging and configuration, check out the official Backstage documentation on Backstage.io. This will provide additional context and guidance on how to effectively manage logging in your Backstage application.