Add logging policy (#5299)

* Add logging policy * Update CONTRIBUTING.md Co-authored-by: Cayman <[email protected]> * Review PR * Address review * review PR --------- Co-authored-by: Cayman <[email protected]>
ChainSafe · Apr 6, 2023 · ddc58ce · ddc58ce
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@@ -150,6 +150,25 @@ We're currently experimenting with hosting the majority of lodestar packages and
   - Error: One or more main functionalities are not working, preventing some functions from working properly.
   - Fatal: One or more main functionalities are not working and preventing the application from fulfilling its duties.
 
+## Logging policy
+
+### Logging Levels
+
+Contributors must choose the log level carefully to ensure a consistent experience for every type of user:
+
+- `error`: Critical issues that prevent the application from functioning correctly or cause significant disruption to users. Examples include failed network connections, crashes, or data corruption.
+- `warn`: Situations that may lead to critical issues if not addressed but do not prevent the application from functioning. Examples include configuration issues, deprecated features, or temporary network disruptions.
+- `info`: General sporadic informational about the node's state. Examples include initialization messages, infrequent periodic status updates, or high-level progress reports.
+- `debug`: Detailed diagnostic information that can help developers or users troubleshoot specific issues. Examples include individual request logs for every REST API, networking interactions, or internal components status changes. Alias to `verbose`.
+
+### Logging guidelines
+
+- Avoid excessive logging. Log messages should be clear and concise, providing enough information to understand the context and severity of the issue.
+- Do not log sensitive data, such as private keys, user credentials, or personal information.
+- Do not log arbitrary data from the network as ASCII or UTF8 at levels higher or equal to `info`.
+- Use clear and concise language. Prefer to log variables in JSON format `log.debug("Action", {slot})` instead of formatting the text yourself `log.debug('slot=${slot}')`.
+- Include only relevant context in log messages, sufficient to debug the issue or action it refers to.
+
 ## Contributing to Grafana dashboards
 
 To edit or extend an existing Grafana dashboard with minimal diff: