X'inhuma metrics, logs, u traces, u meta tuża kull waħda?

Question

Accepted Answer

Dawn huma **tliet stuboli tal-osservabilità**. Jigħu jirrispondu għal mistoqsija differenti: metrics jgħidulekk **li** ħadd ħadd mhux sħiħ, logs jgħidulekk **x'**iseħħ, u traces jgħidulekk **fejn** fid-distributed flow mar il-ħin jew l-iżball.

## Għaliex Huwa Importanti

```text
METRICS  aggregate numbers over time (counters, gauges, histograms)
         → cheap, low cardinality, great for trends & ALERTING
         → e.g. error rate = 2%, p99 latency = 800ms

LOGS     discrete, timestamped events with detail (often structured JSON)
         → rich context for DEBUGGING a specific request
         → e.g. {"level":"error","user":123,"msg":"payment declined"}

TRACES   the path of one request across services, with timing per span
         → shows latency BREAKDOWN and where a call fails
         → e.g. checkout 800ms = api 50ms + db 700ms + email 50ms
```

## Meta tużżahom kull waħda — inċident wieħed

```text
1. METRIC alerts: "checkout p99 latency jumped to 2s"   → you know THERE's a problem
2. TRACE a slow request: 1.8s of 2s is spent in the inventory service
                                                        → you know WHERE it is
3. LOGS of the inventory service at that time: "slow query: missing index"
                                                        → you know WHAT happened
```

Metrics inaqqsuruk għal sintuma u finestra ta' ħin; traces ilokalizzzawhom għal servizz jew sejħa; logs jagħtu l-kawża eżatta. Dirittament għal logs mingħajr metrics jfisser inti tfittex b'lem.

## Kmieni u kardinalità

Metrics huma aggregati, allura jibqgħu irħixa anke bil-iskala — ideali għal dashboards u alerts li dejjem kif jigħu mixgħula. Logs u traces per-event u għaliex, allura huma ġeneralment **kampjonati** u mistoqsija fuq talba matul investigazzjoni.

## Għaliex Huwa Importanti

L-użu tal-istublu żbaljat jispiċċa l-ħin: int ma tistax iżżomm alert b'mod effettiv fuq logs mhux ipproċessati (wisq storbju, wisq għali), u int ma tistax debug ta' request speċifiku li falla minn metrika aggregata. Taf li metrics jiċċettawhom, traces ilokalizzzawhom, u logs jispjegawhom jigħtik post mhux btigin u ripetibli minn "hemm ħadd ħadd mhux sħiħ" għal radix cause.