Concurrency Patterns

Advanced · Concurrency

Composable building blocks for concurrent Go, all built from goroutines + channels. “Don’t communicate by sharing memory; share memory by communicating.”

• concpat1 — worker pool: N workers consume one jobs channel
• concpat2 — fan-in: merge many channels into one
• concpat3 — pipeline: chain stages via channels

Resources

• Go blog: Go Concurrency Patterns: Pipelines and cancellation
• Go blog: Concurrency Patterns
• Go by Example: Worker Pools

Exercises

concpat1 test

concpat1 — worker pool

Show hint

A worker drains its jobs channel until it is closed:

for n := range jobs {
    results <- n * n
}

Source

concpat2 test

concpat2 — fan-in

Show hint

One goroutine per input copies into out; a closer waits for them all:

for _, c := range chans {
    wg.Add(1)
    go func(c <-chan int) { defer wg.Done(); for v := range c { out <- v } }(c)
}
go func() { wg.Wait(); close(out) }()

Source

concpat3 test

concpat3 — pipeline

Show hint

Transform each value, then close out after the input is drained:

for n := range in {
    out <- n * 2
}
close(out)

Source