func main() {
region := "us-east-1"
queueName := "example_queue"
numFetchers := 3
// set up an SQS service instance
// note that you can modify the AWS config used - make your own sqsconsumer.AWSConfigOption
// or just depend on ~/.aws/... or environment variables and don't pass any opts at all
s, err := sqsconsumer.SQSServiceForQueue(queueName, sqsconsumer.OptAWSRegion(region))
if err != nil {
log.Fatalf("Could not set up queue '%s': %s", queueName, err)
}
// set up a context which will gracefully cancel the worker on interrupt
fetchCtx, cancelFetch := context.WithCancel(context.Background())
term := make(chan os.Signal, 1)
signal.Notify(term, os.Interrupt, os.Kill)
go func() {
<-term
log.Println("Starting graceful shutdown")
cancelFetch()
}()
// set up metrics - note TrackMetrics does not run the http server, and uses expvar
exposeMetrics()
ms := expvar.NewInt(fmt.Sprintf("%s.success", queueName))
mf := expvar.NewInt(fmt.Sprintf("%s.fail", queueName))
mt := expvar.NewFloat(fmt.Sprintf("%s.time", queueName))
track := middleware.TrackMetrics(ms, mf, mt)
// wrap the handler
handler := middleware.ApplyDecoratorsToHandler(processMessage, track)
// start the consumers
log.Println("Starting queue consumers")
wg := &sync.WaitGroup{}
wg.Add(numFetchers)
for i := 0; i < numFetchers; i++ {
go func() {
// create the consumer and bind it to a queue and processor function
c := sqsconsumer.NewConsumer(s, handler)
// start running the consumer with a context that will be cancelled when a graceful shutdown is requested
c.Run(fetchCtx)
wg.Done()
}()
}
// wait for all the consumers to exit cleanly
wg.Wait()
log.Println("Shutdown complete")
}
func (w *worker) Run(ctx context.Context) {
sqs, err := sqsconsumer.SQSServiceForQueue(w.Queue)
if err != nil {
log.Fatalf("ERROR Could not set up queue '%s': %s\n", w.Queue, err)
}
// create the consumer bound to a queue and processor function and start running it with a context that will be cancelled when a graceful shutdown is requested
log.Printf("Starting consumer for SQS queue: %s", w.Queue)
sc := sqsconsumer.NewConsumer(sqs, w.HandleMessage)
sc.Run(ctx)
log.Println("Shutdown complete")
}