Deforester

What is Deforester?

Deforester is a logging library for the Janet programming language. It implements a modern production logging pipeline that moves events through processors, applies formatting, and writes output to a destination. By default, it outputs to standard error so that logging failures do not crash running programs.

The library supports structured logging with configurable formatters and writers. Users can route logs to files, pipe them to external services, or format them as newline-delimited JSON for easy consumption by tools like jq. Filters allow developers to control which log levels are evaluated before processing.

Deforester includes context management functions for tracking execution duration, modifying fiber contexts, and capturing logs during tests. Developers can override timestamps or message fields to create stable snapshot tests. Custom processors can be added to forward specific events, such as errors, to third-party monitoring systems.

Deforester features

• Structured event pipeline with processors and formatters
• Configurable file and standard error writers
• Newline-delimited JSON output format
• Context tracking for execution duration and fiber scopes
• Test helpers to capture and override log output
• Level filtering to skip unevaluated arguments
• Custom processor support for routing specific events

Who uses Deforester and for what

• Adding structured debugging output to Janet scripts
• Capturing application logs for local file analysis
• Writing unit tests with controlled log snapshots
• Routing error events to external monitoring dashboards
• Tracking function execution time in production workflows

Deforester FAQ

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