Piye carane Redis lists bisa digunakake lan kepiye penggunaane kanggo queues?

Question

Accepted Answer

Redis **lists** minangka koleksi string sing urut (diimplementasikake minangka linked lists) kanthi push/pop cepet ing rong ujung. Umume digunakake kanggo ngimplementasikake **queues** lan **stacks** — cara sederhana lan populer kanggo nggunakake Redis demi job processing lan data sing urut.

## Operasi list

```bash
LPUSH mylist "a"        # push to the LEFT (head)
RPUSH mylist "b"        # push to the RIGHT (tail)
LPOP mylist             # pop from the LEFT
RPOP mylist             # pop from the RIGHT
LRANGE mylist 0 -1      # get a range (0 to -1 = all elements)
LLEN mylist             # length
LINDEX mylist 0         # element at an index
```

Push/pop ing salah siji ujung iku cepet (O(1)). `LRANGE` maca rentang. Operasi kasebut nggawe lists ideal kanggo data sing urut lan mirip queue.

## Implementasi queue (FIFO)

```bash
# Producer adds jobs; consumer processes them in order (FIFO)
LPUSH job_queue "job1"    # producer pushes to the left
LPUSH job_queue "job2"
RPOP job_queue            # consumer pops from the right => "job1" (first in, first out)
# push left + pop right = FIFO queue
```

A **queue** (first-in-first-out): producers `LPUSH` (nambah ing siji ujung), consumers `RPOP` (mbusak saka ujung liyane) — pola job queue Redis klasik.

## Blocking pops (efficient consumers)

```bash
# BRPOP blocks (waits) until an element is available — no busy polling
BRPOP job_queue 5     # wait up to 5 seconds for a job (0 = wait forever)
# → the consumer efficiently waits for work instead of repeatedly polling
```

**Blocking pops** (`BLPOP`/`BRPOP`) ngidini consumer nunggu kanthi efisien kanggo item anyar tinimbang terus-terusan polling — penting kanggo queue workers sing responsif lan efisien.

## Stack lan pola liyane

```bash
# STACK (LIFO): push and pop from the SAME end
LPUSH stack "a"; LPOP stack    # last in, first out

# capped list (e.g. keep the last 100 items — recent activity feed)
LPUSH recent "event"; LTRIM recent 0 99   # keep only indices 0-99
```

## Kenapa iki penting

Redis lists lan panggunaane kanggo queues minangka pengetahuan Redis sing praktis lan umum diaplikasikake, mula ngerti babagan iki iku berharga kanggo akeh use cases nyata.

Lists (koleksi string sing urut kanthi **push/pop O(1) cepet ing rong ujung**) iku versatile, nanging aplikasi paling penting yaiku mengimplementasikake **queues** — nggunakake `LPUSH`/`RPOP` (utawa sebaliknya) kanggo mbangun **FIFO job queue** ing ngendi producers nambah pekerjaan lan consumers ngproses kanthi urut, pola sederhana lan abot banget umum kanggo background job processing, task distribution, lan decoupling producers saka consumers.

Iki ndadekake Redis populer minangka message/job queue enteng tanpa perlu dedicated queue system kanggo kebutuhan sing luwih sederhana.

Ngerti babagan **blocking pops** (`BLPOP`/`BRPOP`) utamane penting kanggo efficient queue workers — iku ngidini consumers nunggu item anyar tinimbang polling sing boros, nggawe workers responsif lan efisien (teknik praktis kunci kanggo implementasi queue nyata).

Ngerti pola liyane — **stacks** (LIFO, push/pop ujung padha) lan **capped lists** (nggunakake `LTRIM` kanggo keep only recent N items, ideal kanggo activity feeds lan recent-items lists) — nambah kegunaan lists.

Amarga job queues lan data urut iku kebutuhan umum, lan amarga Redis lists ngatur cara sederhana, cepet, populer kanggo mengimplementasikake queues (kanthi blocking pops kanggo efficient consumers), stacks, lan recent-items feeds, ngerti Redis lists lan pola queue iku pengetahuan berharga lan asring diaplikasikake kanggo nggunakake Redis ing aplikasi nyata, salah siji penggunaan praktis paling umum Redis ngajak caching lan building block kanggo background processing lan decoupled architectures.