Logging

What it is

• SnelDB uses the tracing ecosystem for structured, leveled logs.
• Logs are emitted to stdout and to a daily‑rotated file, with independent levels.
• Levels and output directory are configured via the config file.

Core pieces

• Initializer — sets up tracing_subscriber layers for stdout and file.
• Config — [logging] section controls log_dir, stdout_level, and file_level.
• Levels — error, warn, info, debug, trace.

How it works

• Startup

  • logging::init() is called from main.rs before starting frontends.
  • Reads CONFIG.logging to build filters and writers.
  • Installs two layers: ANSI stdout and file appender (sneldb.log, daily rotation).

• Emitting logs

  • Use tracing::{error!, warn!, info!, debug!, trace!} in code.
  • Prefer spans (e.g., #[instrument]) to capture context around operations.

Configuration

Example snippet from config.toml:

[logging]
log_dir = "../data/logs"
stdout_level = "debug"
file_level = "error"

• stdout_level: global level for console logs.
• file_level: global level for file logs.
• log_dir: directory where sneldb.log is created (daily rotation).

Why this design

• Structured logs with levels and spans ease debugging and operations.
• Separate stdout/file control supports local development and production hygiene.

Operational notes

• Tune levels per environment (e.g., stdout_level=warn in prod).
• Ensure log_dir exists and is writable; it is created on first write by the appender.
• Use targets when necessary to scope logs for noisy modules.

Further Reading

• tracing crate docs
• tracing_subscriber filters and formatters