How to Achieve Minimal Overhead for Disabled Trace Logging in Go?

How to Implement Trace Logging in Go with Minimal Overhead for Disabled Log Statements

In critical paths, it's valuable to retain low-level debug/trace logging statements. These can be enabled by runtime configuration, allowing them to be turned off in production (to avoid performance penalties) while being enabled in a production environment (such as for debugging or testing).

The Need for Minimal Cost

This approach requires that the cost of encountering a disabled log statement on a critical path must be extremely low, ideally just a boolean check.

Go's Limitations

Unlike C/C 's LOG macro, Go's logging does not provide a way to avoid evaluating arguments until checking a flag. This poses a challenge for avoiding performance penalties when logs are disabled.

Approaches in Go

• EnabledLogger: Implies the log.Logger interface methods but checks enabled status before delegating to the actual logger. This approach is adequate but still evaluates arguments.
• Wrapper Types: Uses wrapper types (such as Stringify) to defer function calls and evaluation until the logger is enabled.
• Explicit Enabled Check: Manually checks if the logger is enabled before calling the expensive function to format.
• Dynamic Logger Swapping: Replaces the entire logger at runtime with an implementation that checks for interfaces and delays formatting.
• Build Constraints: Swaps out the logger entirely at build time using build constraints.
• Code Generation: Introduces a separate debug build through code generation, using tools like gofmt, text/template, or AST parsing. This approach is not suitable for runtime configuration but can provide a dedicated debug build.

Conclusion

The optimal approach depends on the specific needs of the application. For runtime configurable tracing, the EnabledLogger pattern or Dynamic Logger Swapping are suitable. For minimal overhead and terse syntax, assigning the logger to a bool variable can be effective. Code generation provides a solution for separate debug builds.

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