Apa saja pola konkurensi umum ing Go?

Question

Accepted Answer

goroutine lan channel Go aktifake siji set saka **pola konkurensi** sing sudah mapan, sing ngrampungake masalah umum — distribusi kerja, fan-out/fan-in, pipeline, lan rate limiting. Ngerti pola-pola idiomatik iki ndadekake sampeyan bisa membangun sistem konkuren sing bener lan efisien.

## Mengapa penting

```go
func workerPool(jobs <-chan int, results chan<- int, numWorkers int) {
    var wg sync.WaitGroup
    for w := 0; w < numWorkers; w++ {     // a FIXED number of workers
        wg.Add(1)
        go func() {
            defer wg.Done()
            for job := range jobs {        // each worker pulls jobs until the channel closes
                results <- process(job)
            }
        }()
    }
    wg.Wait()
    close(results)
}
```

Siji **worker pool** njalanake jumlah tetep goroutine sing ngonsumsi saka channel job sing dibarengi — mbatesi konkurensi (contone, aja mbuka 10.000 koneksi DB; gunakake 10 worker). Iki pola sing paling penting kanggo ngontrol panggunaan sumber daya.

## Fan-out / fan-in

```text
Fan-out: distribute work across MULTIPLE goroutines (parallelize)
Fan-in:  MERGE results from multiple goroutines back into one channel
```

```go
// fan-in: merge several channels into one
func merge(channels ...<-chan int) <-chan int {
    out := make(chan int)
    var wg sync.WaitGroup
    for _, ch := range channels {
        wg.Add(1)
        go func(c <-chan int) {
            defer wg.Done()
            for v := range c { out <- v }   // forward each channel's values to out
        }(ch)
    }
    go func() { wg.Wait(); close(out) }()    // close out when all sources are drained
    return out
}
```

## Pipeline — tahapan sing disambung karo channel

```go
// each stage is a goroutine: receives from an input channel, sends to an output channel
func generate(nums ...int) <-chan int {
    out := make(chan int)
    go func() { for _, n := range nums { out <- n }; close(out) }()
    return out
}
func square(in <-chan int) <-chan int {
    out := make(chan int)
    go func() { for n := range in { out <- n * n }; close(out) }()
    return out
}
// compose: square(generate(1,2,3)) → a streaming pipeline
for result := range square(generate(1, 2, 3)) { fmt.Println(result) }
```

Siji **pipeline** ngrantai tahapan pemrosesan liwat channel — data ngerusakake, saben tahapan ngowahi iku kanthi konkuren.

## Rate limiting

```go
limiter := time.Tick(200 * time.Millisecond)   // a tick every 200ms
for req := range requests {
    <-limiter                                    // wait for the next tick before proceeding
    go handle(req)                                // → at most 5 requests/second
}
```

## Pembatalan kanthi context (lintas-cutting)

```go
select {
case result := <-work:
case <-ctx.Done():    return   // stop on cancellation — prevents leaks
}
```

## Mengapa penting

Pola-pola konkurensi iki minangka toolkit praktis kanggo ngbangun sistem konkuren Go sing nyata, ngowahi goroutine lan channel mentah dadi solusi terstruktur lan bener kanggo masalah sing mbalik-mbaliki.

**worker pool** luwih penting — iku mbatesi konkurensi kanggo mulei sumber daya terbatas (koneksi basis data, batas laju API, memori), nyegah kesalahan umum saka nggawe goroutine tanpa batas sing nghabisi sistem. **Fan-out/fan-in** nggandeng kerja lan ngggabung asil; **pipeline** nggawe transformasi data streaming kanthi bersih; **rate limiting** ngontrol throughput.

Digabungake karo **pembatalan berbasis context** (kanggo nyegah ngocoran goroutine), pola-pola iki minangka cara layanan Go produksi nanggulangi konkurensi kanthi aman lan efisien.

Pamahaman babagan iki — lan luwih utama ngerti kanggo mbatesi konkurensi karo worker pool nimbang ngluncurake goroutine tanpa batas — minangka tandha kompetensi Go senior lan topik interviu tingkat lanjut sing asring dipilih, amarga konkurensi naif (goroutine tanpa batas, ngocoran, race) minangka sumber kegagalan produksi sing umum.