Kif Redis jimmexxa l-memorja?

Question

Accepted Answer

Billi Redis taħżen id-data f'RAM, **l-ġestjoni tal-memorja** hija kritika — il-fehim tal-limitu `maxmemory`, **il-politiki tal-evizzjoni**, l-ottimizzazzjoni tal-memorja, u l-monitoraġġ huma essenzjali għall-korsija tal-Redis b'mod affidabbli mingħajr ma jippruvaw il-memorja.

## maxmemory u l-evizzjoni

```text
Set a memory limit so Redis doesn't consume all RAM:
  maxmemory 2gb                       # cap Redis at 2GB
  maxmemory-policy allkeys-lru        # what to do when the limit is reached

When the limit is hit, Redis EVICTS keys per the policy (or rejects writes):
  allkeys-lru   → evict least-recently-used (any key) — common for a pure cache
  allkeys-lfu   → evict least-frequently-used
  volatile-lru  → evict LRU among keys WITH a TTL only
  volatile-ttl  → evict keys closest to expiry
  noeviction    → reject writes when full (good if Redis holds important data)
```

It-tistabbiliment ta' `maxmemory` plus **politika ta' evizzjoni** jikkontrolla l-imġiba meta timla' l-memorja — essenzjali biex tipprevjeni lil Redis milli jistħaqqaq il-memorja tas-sistema jew jintefa'.

## Monitoraġġ tal-memorja

```bash
INFO memory               # used_memory, peak, fragmentation ratio, etc.
MEMORY USAGE key          # memory used by a specific key
MEMORY DOCTOR             # diagnostics/recommendations
DBSIZE                    # number of keys
# watch: used_memory vs maxmemory, evicted_keys, fragmentation
```

## Tekniki tal-ottimizzazzjoni tal-memorja

```text
✓ Set TTLs → expire data that's no longer needed (don't let data accumulate forever)
✓ Use efficient data structures → small hashes/lists/sets use compact encodings (ziplist/
  listpack) → much less memory than many separate keys
✓ Shorter key names (minor, but adds up at scale)
✓ Store only what you need; consider compression for large values
✓ Avoid huge keys (a single huge value/collection) — they cause latency spikes
```

## Għaliex il-memorja importanti fi Redis

```text
RAM is LIMITED and more expensive than disk. Running out of memory →
  evictions (cache misses), rejected writes, or crashes.
→ Capacity planning, eviction policy, TTLs, and monitoring keep Redis healthy.
```

## Għaliex dan importanti

L-fehim tal-ġestjoni tal-memorja tal-Redis huwa importanti għal **l-korsija tal-Redis b'mod affidabbli**, għaliex Redis taħżen id-data f'RAM limitat u relattivament għali, għalhekk l-ġestjoni tal-memorja hija essenzjali biex tipprevjeni lil Redis milli tħarruġ (li tikkawża evizzjonijiet, kitbiet rifjutati, jew ħsara).
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