Go Structured Logging Libraries

Zerolog is a structured logging library for Go designed for high-performance event capture and observability. It focuses on generating machine-readable JSON output while minimizing memory overhead through zero-allocation buffer encoding and strongly-typed field validation. The library distinguishes itself by providing a chainable, context-aware interface that allows developers to bind trace identifiers and metadata directly to request lifecycles. It supports complex diagnostic workflows by enabling independent logger instances, custom output routing to multiple concurrent destinations, and event-based sampling to manage log volume and storage costs. Beyond its core structured output, the toolkit includes features for local development, such as transforming machine-readable data into colorized, human-friendly console text. It also maintains compatibility with existing systems by providing adapters that wrap standard library logging interfaces, allowing for the integration of modern diagnostic capabilities into legacy codebases.

Zap is a high-performance structured logging library designed for production environments. It provides a framework for generating machine-readable logs that minimize memory overhead and CPU usage, allowing for efficient event analysis and system monitoring. The library distinguishes itself through a focus on zero-allocation logging, utilizing buffer pooling to reduce garbage collection pressure during high-frequency operations. It enforces strict data typing through compile-time checks and structured field encoding, which ensures consistent output without the performance cost of reflection-based inspection. The architecture supports complex distributed systems by decoupling the logging interface from output sinks and enabling dynamic, atomic level switching across concurrent threads. It also includes capabilities for contextual error tracking and diagnostic data collection to assist in identifying the root causes of application failures.

Logrus is a structured logging library for Go that produces machine-readable output using key-value pairs and JSON formatting. It serves as a pluggable logging framework providing a thread-safe event logger with configurable mutex locking to manage concurrent writes across multiple goroutines. The project distinguishes itself through a pluggable hook system that routes log entries to external services or custom destinations. It also features a contextual logger capable of attaching persistent metadata and request-scoped fields to entries to improve traceability. The framework covers broad observability capabilities, including call site tracking for source code location, severity-based verbosity control, and the ability to redirect output from the standard library into a structured pipeline. It supports multiple output formats, such as JSON and plain text with ANSI color styling, and includes mechanisms for log data redaction and log-to-metric translation. Performance is managed through memory buffer pooling and deferred log evaluation to reduce allocation overhead.

This is a structured logging library designed to produce logs using key-value pairs, severity levels, and machine-readable formats. It provides a toolkit for creating logs that are consistent for both human review and machine parsing. The project is distinguished by its focus on terminal visualization, using a styling system to apply colors and prefixes to log entries for improved readability in consoles. It also includes a specialized adapter to convert standard library log calls into structured events by inferring severity levels from message prefixes. The library manages metadata through contextual sub-loggers that attach persistent attributes and automatic source location information to entries. It supports multiple serialization formats, including JSON and logfmt, and provides source attribution by analyzing the call stack to identify the origin of log events. The system integrates with the standard slog package via a custom handler to route structured logs through its formatting engine.