simple queue manager

gistfile1.txt

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R: {{device_1 apn [HSV CL] asdf} 2 ca1ac428-86f2-413c-52cf-8059b16e6883}
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R: {{device_1 apn [HSV CL] asdf} 3 3bb190ad-f5fa-439d-5257-06ac5ddb4511}
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R: {{device_1 apn [HSV CL] asdf} 3 21e8a49d-e9e4-4cf6-71d4-c25677f30664}
R: {{device_1 apn [HSV CL] asdf} 3 4f5c9e09-94ed-4da9-6504-b4524ba1d1b8}
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R: {{device_1 apn [HSV CL] asdf} 3 6a22879a-64ca-40fe-6417-613e9c69458c}
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R: {{device_1 apn [HSV CL] asdf} 3 e8d629eb-541f-4a00-50aa-4ffd473c129f}
R: {{device_1 apn [HSV CL] asdf} 3 ca1ac428-86f2-413c-52cf-8059b16e6883}
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F: {{device_1 apn [HSV CL] asdf} 4 9d35fbda-4965-4afe-50a1-e852101cf2b5}
F: {{device_1 apn [HSV CL] asdf} 4 5d4f677b-1d9b-47d8-4fe8-7b7c9e6e2b59}

worker.go

/* 
if you find this: this is a learning project...
I obviously don't know much go yet and will be ashamed of this
code in about 2-3 days. I obvioysly forgot to delete this gist...
*/

package web

import (
	"fmt"
	"math/rand"
	"time"

	"github.com/nu7hatch/gouuid"
)

type deviceRequestJob struct {
	req   deviceRequest
	tries int
	jid   string
}

func newDeviceRequestJob(r deviceRequest) deviceRequestJob {
	var jid string
	u4, err := uuid.NewV4()
	if err != nil {
		fmt.Println("error:", err)
		jid = fmt.Sprintf("failing-uuid-%d", rand.Int())
	} else {
		jid = u4.String()
	}

	return deviceRequestJob{
		req:   r,
		tries: 0,
		jid:   jid,
	}
}

type manager struct {
	PoolSize   int
	queue      chan deviceRequestJob
	maxRetries int
}

func newManager(poolSize int) *manager {
	m := &manager{
		queue:      make(chan deviceRequestJob, 1),
		PoolSize:   poolSize,
		maxRetries: 3,
	}
	go m.run()
	return m
}

func (m *manager) Queue(r deviceRequest) {
	m.queue <- newDeviceRequestJob(r)
}

func (m *manager) run() {
	inbox := make([]deviceRequestJob, 0, 1000)
	pool := make([]*worker, m.PoolSize)
	done := make(chan *worker)
	err := make(chan workerError)

	for i, _ := range pool {
		pool[i] = &worker{done: done, err: err}
	}

	for {
		select {
		case r := <-m.queue:
			r.tries++
			inbox = append(inbox, r)
		case w := <-done:
			pool = append(pool, w)
		case e := <-err:
			job := e.job
			job.tries++
			if job.tries > m.maxRetries {
				fmt.Printf("F: %v\n", job)
				continue
			}
			fmt.Printf("R: %v\n", job)
			pool = append(pool, e.worker)
			inbox = append(inbox, job)
		}

		if len(inbox) > 0 && len(pool) > 0 {
			w := pool[0]
			pool = pool[1:]
			j := inbox[0]
			inbox = inbox[1:]
			go w.work(j)
		}
	}
}

type worker struct {
	done chan *worker
	err  chan workerError
}

func (w *worker) work(j deviceRequestJob) {
	time.Sleep(5 * time.Millisecond)
	if rand.Intn(2) == 0 {
		w.err <- w.newError("something happened", j)
	} else {
		fmt.Printf("D: %v\n", j)
		w.done <- w
	}
}

func (w *worker) newError(m string, j deviceRequestJob) workerError {
	return workerError{
		msg:    m,
		worker: w,
		job:    j,
	}
}

type workerError struct {
	worker *worker
	job    deviceRequestJob
	msg    string
}

func (e workerError) Error() string {
	return e.msg
}