Piyé carane Redis replication lan high availability bisa manggon?

Question

Accepted Answer

Redis nyediyakake **high availability** liwat **replication** (replica nyalin data), **Redis Sentinel** (monitoring failover otomatis), lan **Redis Cluster** (sharding + replication). Ngerti iki penting kanggo mbukak Redis kanthi andal ing production.

## Replication — primary lan replicas

```text
PRIMARY (master) → handles writes; asynchronously replicates data to replicas
REPLICAS (slaves) → copies of the primary's data; can serve READS (read scaling)

Write → Primary → async replication → Replicas (eventually consistent)
  ✓ Redundancy (replicas have copies) + read scaling (reads offloaded to replicas)
  ✗ Replication is ASYNC → a small lag; a failover could lose very recent writes
```

Replicas ngsalin data primary kanthi asinkron — nyediyakake redundancy lan read scaling (baca bisa menyang replicas), nanging ana lag replication cilik.

## Redis Sentinel — failover otomatis

```text
Replication alone doesn't auto-recover if the PRIMARY fails. REDIS SENTINEL adds:
  → MONITORING — Sentinels watch the primary and replicas
  → AUTOMATIC FAILOVER — if the primary fails, Sentinels elect a replica as the new primary
  → SERVICE DISCOVERY — clients ask Sentinel for the current primary address
→ Sentinel provides high availability (auto-failover) for a non-clustered setup.
  (Run multiple Sentinels — a majority must agree — to avoid false failovers.)
```

**Sentinel** nonton setup lan nindakake **failover otomatis** (nggangkat replica yen primary gagal) — ngubah kegagalan primary dadi gangguan singkat tinimbang outage.

## Redis Cluster — sharding + HA

```text
REDIS CLUSTER → for scaling beyond one server's memory AND high availability:
  → SHARDS data across multiple primaries (each holds a subset via hash slots, 16384 total)
  → each primary has replicas (HA — a replica takes over if its primary fails)
  → scales horizontally (more memory/throughput) + built-in failover
→ Use Cluster when data exceeds one node's RAM or you need to scale writes.
```

## Piyé iki Penting

Ngerti Redis replication lan high availability penting kanggo **mbukak Redis kanthi andal ing production**, mangkono iku ilmu tingkat senior sing berharga kanggo deployment Redis production.

Amarga Redis asring nyimpen data penting (cache sing ilange nyebabake spike beban, session, queue), mesthiake availability lan redundancy. **Replication** (replicas ngsalin data primary kanthi asinkron) nyediyakake fondasi — redundancy (replicas nyimpen salinan) lan read scaling (transfer baca menyang replicas) — nanging ngerti sifate **asinkron** (lag cilik, kemungkinan ilange write paling anyar ing failover) penting kanggo mikirake consistency. **Redis Sentinel** kunci kanggo high availability ing setup non-clustered: nambah **monitoring lan failover otomatis** (nggangkat replica yen primary gagal) plus service discovery, ngubah kegagalan primary dadi gangguan singkal tinimbang outage — penting kanggo sistem kudu tetep available (lan mbukak multipel Sentinel kanggo majority agreement nyegah failover palsu). **Redis Cluster** ngatasi scaling lan HA: **sharding data ing multipel primary** (liwat hash slot, scaling luwih saka memory server siji lan write throughput) kanthi replicas kanggo failover — perlu yen data luwih saka RAM node siji utawa write kudu scale.

Ngerti mana sing digunakake (Sentinel kanggo HA dataset siji, Cluster kanggo sharding + HA ing scale) nuduhake pertimbangan operasional sing apik.

Sajrone production Redis kudu available lan bisa perlu scale, lan sambongane replication (redundancy/read scaling), Sentinel (failover otomatis), lan Cluster (sharding + HA) minangka mekanisme Redis kanggo reliability lan scale, ngerti Redis replication lan high availability minangka ilmu tingkat senior penting kanggo deploy Redis kanthi andal, kepedulian production sing asring penting lan topik nuduhake pangerten piyé carane mbukak Redis minangka bagian dependable infrastruktur tinimbang single point of failure.