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main.go
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main.go
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package main
import (
"context"
"flag"
"fmt"
"log"
"runtime"
"github.com/MixedMessages/taskrunner"
)
// HelloWorldTask wraps a number that prefixes the hello world message
// generated by the task.
type HelloWorldTask struct {
num int
}
// Task implements the taskrunner.Task interface.
// Returns a string that says Hello World! with a number prefixed.
func (p *HelloWorldTask) Task(context.Context) (interface{}, error) {
return fmt.Sprintf("%d: Hello World!", p.num), nil
}
func main() {
num := flag.Int("num", 100, "The number of hello worlds to print.")
workers := flag.Int("workers", runtime.NumCPU()+1, "The number of concurrent workers to start.")
flag.Parse()
if *num < 0 {
log.Fatal("num must be a positive integer")
}
// Create the runner.
runner, err := taskrunner.NewTaskRunner(taskrunner.OptionMaxGoroutines(*workers))
if err != nil {
panic(err.Error())
}
// Start the runner.
if err := runner.Start(); err != nil {
panic(err.Error())
}
// Collect the promises after running the HelloWorld tasks.
promises := make([]taskrunner.Promise, *num)
for i := 0; i < *num; i++ {
promises[i] = runner.Run(context.TODO(), &HelloWorldTask{i})
}
// Handle the promises.
for i := range promises {
res, err := promises[i]()
if err != nil {
fmt.Printf("promise failure: res=%+v - err=%+v", res, err)
}
str, ok := res.(string)
if !ok {
log.Printf("unexpected promise return type - expected string - got %T", res)
}
log.Println(str)
}
}