Ni mifumo ipi ya upinga hatari inapolinda huduma ndogo (circuit breaker, retry, timeout, bulkhead)?

Question

Accepted Answer

Katika mfumo uliogawanywa, **kila kitu kinashindwa hatimaye**. Mifumo ya upinga hatari inazuia kosa moja la kueneza kwa njia ya kumkosa kila kitu.

## Mifumo ya msingi

- **Timeout** — kamwe usichague kwa muda usio na kikomo kwa jibu.
- **Retry** — jaribu tena maadhimisho ya muda mfupi, na backoff + jitter.
- **Circuit breaker** — acha kupigia huduma inayoshindwa ili iweze kurejea.
- **Bulkhead** — tenga rasilimali ili tegemezi moja polepole isiweze kumoza nyingine.

## Mfano wa Circuit breaker

```js
const breaker = new CircuitBreaker(callPaymentService, {
  timeout: 3000,                 // fail the call after 3s
  errorThresholdPercentage: 50,  // open if >50% of calls fail
  resetTimeout: 10000            // after 10s, try one request (half-open)
});
breaker.fallback(() => ({ status: 'queued' })); // graceful degradation
```

## Hali ya Circuit breaker

```text
CLOSED ──(failures exceed threshold)──▶ OPEN
  ▲                                       │ (after resetTimeout)
  │ (trial succeeds)                       ▼
  └────────────── HALF-OPEN ◀──────────────┘
                (one trial request)
```

## Bulkhead

```text
[ pool A: 10 threads ]  → payment calls
[ pool B: 10 threads ]  → search calls
If search hangs, it drains pool B only — payments keep working.
```

## Mtego

**Ujaribu upya bila backoff** huongeza mzigo kwenye huduma inayokamatia tayari (upepo wa ujaribu upya). Daima ongeza backoff, jitter, na kiwango cha ujaribu upya.

## Kwa nini ina umuhimu

Mifumo hii ndiyo inayobadilisha kosa moja lisilovezekana katika huduma kuwa sifa iliyoharibika badala ya kuwa homa nzima ya wavuti.

Inasfanya pamoja: timeouts huangazia kusubiri, circuit breakers husimamisha kupiga huduma zenye kifo, bulkheads hukamatia radi ya mlipuko, na majibu upya hurejesha kutoka kwa matatizo mafupi — ondoa moja yoyote na maadhimisho bado humkosa.