go / expert
Snippet
Biased Priority Channel Selection Pattern for High-Throughput Pipelines
Standard Go select blocks evaluate ready cases pseudo-randomly to avoid starvation. To build deterministic priority scheduling, a non-blocking select with a default clause must first probe high-priority channels before falling back to a multi-channel blocking select statement.
snippet.go
go
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package mainimport ("context""fmt""time")func PrioritySelect(ctx context.Context, highPri <-chan int, lowPri <-chan int) {for {select {case <-ctx.Done():fmt.Println("Shutting down priority consumer")returncase item := <-highPri:fmt.Println("High priority item processed:", item)continuedefault:}select {case <-ctx.Done():fmt.Println("Shutting down priority consumer")returncase item := <-highPri:fmt.Println("High priority item processed:", item)case item := <-lowPri:fmt.Println("Low priority item processed:", item)}}}func main() {ctx, cancel := context.WithTimeout(context.Background(), 50*time.Millisecond)defer cancel()high := make(chan int, 10)low := make(chan int, 10)high <- 100low <- 1high <- 200PrioritySelect(ctx, high, low)}
Breakdown
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select { case item := <-highPri: ... default: }
Executes a non-blocking check on the high-priority channel first; if message exists, consumes it immediately without considering low-priority channels.
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select { case <-ctx.Done(): ... case item := <-highPri: ... case item := <-lowPri: ... }
Fallback blocking select that suspends execution until data arrives on any channel or the context finishes.