Observability ialah keupayaan untuk memahami keadaan dalaman sistem daripada output luarannya — melalui logs, metrics, dan traces. Ia penting untuk mengendalikan, menyahpepijat, dan menyelenggara sistem (terutamanya yang teragih), di mana anda tidak boleh menguruskan apa yang anda tidak nampak.
Tiga tonggak observability
LOGS → timestamped records of events (what happened) → detailed, for debugging specific issues
METRICS → numerical measurements over time (CPU, latency, request rate, error rate) →
aggregate health/performance; dashboards; alerting
TRACES → follow a request's path through the system (across services) → understand flows,
find bottlenecks/failures in DISTRIBUTED systems (which service was slow?)
→ together: understand WHAT happened, the OVERALL state, and the PATH of requests.
