# Observability

## Logs

- Unify code to log - configure to include module name: https://hexdocs.pm/logger/Logger.html
- Failures
- Audit logs

## Metrics

- Take time to calculate - they aren't free
- Measure time
- If something happens: do the metrics reflect the state you envisioned?
    - Yes: good
    - No: bad metric


- Types of metrics
    - Business
        - Sales
        - Marketing
    - System
        - CPU
        - RAM
        - Process count
        - Performance
        - Availability
        - ...
    - Product

- Metrics kinds
    - Leading (short time): test hypothesis 
    - Lagging (long time): whether actions were successful

## Alarms

https://www.erlang.org/doc/apps/sasl/alarm_handler.html