Observability

Log Levels Guide

Choose debug, info, warn and error levels so production logs stay useful during incidents. Last updated September 1, 2026.

Choose debug, info, warn and error levels so production logs stay useful during incidents. This Formalint reference is designed for developers, DBAs, platform engineers and support teams who need an ordered troubleshooting path.

The page keeps the work practical: collect evidence, avoid leaking secrets, make the smallest safe change and leave a note another engineer can repeat.

When to use it

• A deployment, policy, incident or integration behaves differently than expected.
• You need a repeatable command or checklist before changing production behavior.
• You want to keep the debugging note understandable for another engineer.

Practical workflow

Command or evidence sample

debug: internal troubleshooting
info: normal business event
warn: recoverable risk
error: failed user-visible operation

Review checklist

1. Write down the affected host, endpoint, job, service or browser context.
2. Redact tokens, session cookies, passwords and customer identifiers.
3. Capture timestamps, headers, logs or command output before changing settings.
4. Prefer staged rollout, report-only mode, preview checks or single-URL cache purges where possible.
5. Link the final note to a related Formalint page so the next step is obvious.

Common mistake

The common mistake is logging more text without making the event searchable, safe and tied to ownership.

Formalint's rule for these areas is simple: make the hidden system boundary visible before you tune it.

Related Formalint references

Continue with Api Correlation Id Logging Guide, Linux Journalctl Guide, Nginx Access Log Analysis Guide.

Frequently asked questions