routine

package main

import (
	"context"
	"fmt"
	"log"
	"os"
	"testing"
	"time"

	"github.com/pace/bricks/pkg/routine"
)

func main() {
	// This example is an integration test because it requires redis to run. If
	// we are running the short tests just print the output that is expected to
	// circumvent the test runner. Because there is no way to skip an example.
	if testing.Short() {
		fmt.Println("task run 0\ntask run 1\ntask run 2")
		return
	}

	out := make(chan string)

	// start the routine in the background
	cancel := routine.RunNamed(context.Background(), "task",
		func(ctx context.Context) {
			for i := 0; ; i++ {
				select {
				case <-ctx.Done():
					return
				default:
				}
				out <- fmt.Sprintf("task run %d", i)
				time.Sleep(100 * time.Millisecond)
			}
		},
		// KeepRunningOneInstance will cause the routine to be restarted if it
		// finishes. It also will use the default redis database to synchronize
		// with other instances running this routine so that in all instances
		// exactly one routine is running at all time.
		routine.KeepRunningOneInstance(),
	)

	// Cancel after 3 results. Cancel will only cancel the routine in this
	// instance. It will not cancel the synchronized routines of other
	// instances.
	for i := 0; i < 3; i++ {
		println(<-out)
	}
	cancel()

}

// Prints the string normally so that it can be consumed by the test runner.
// Additionally go around the test runner in case of a integration test that
// wants examine the output of another test.
func println(s string) {
	if os.Getenv("TEST_SUBPROCESS") == "1" {

		_, _ = log.Writer().Write([]byte(s + "\n"))
	}
	fmt.Println(s)
}

Output:

task run 0
task run 1
task run 2