Thanks for comments. The status00 should be not-buffered (status00 =
make(chan *Data)); was rate limiting on two channels.
On Sunday, August 28, 2016 at 8:16:50 PM UTC+4:30, Henrik Johansson wrote:
>
> The race is between the len call and the use of the channel. Entries can
> have been added in between.
>
> On Sun, Aug 28, 2016, 17:40 dc0d <kaveh.sh...@gmail.com <javascript:>>
> wrote:
>
>> Would you please elaborate on that?
>>
>> As I understand it there is no concurrent use of len happening here. It's
>> a for loop and all calling to len is happening sequentially. Unless the
>> channels make the code inside cases of one select statement concurrent -
>> which will be super confusing for me.
>>
>>
>> On Sunday, August 28, 2016 at 8:03:10 PM UTC+4:30, Jan Mercl wrote:
>>
>>> Using len(ch) like this in a concurrency scenario is a big no because
>>> then the value you get carries 0 bits of useful information. It's not a
>>> data race, it's worse, the race is semantic and not fixable without
>>> removing the use of len(ch).
>>>
>>> On Sun, Aug 28, 2016, 17:26 dc0d <kaveh.sh...@gmail.com> wrote:
>>>
>> TL;DR
>>>>
>>>> Does assigning a (buffered) channel, already in a variable, to a second
>>>> variable, affects the result of len function?
>>>>
>>>> Long version:
>>>> What is happening here? - Code at the end; Go 1.7.
>>>>
>>>> *Output 1*:
>>>>
>>>> Nine times:
>>>> [ info ] 2016/08/28 19:51:28 LEN_BEFORE=0
>>>>
>>>> [ info ] 2016/08/28 19:51:28 LEN=7
>>>>
>>>> [ info ] 2016/08/28 19:51:28 S00=7
>>>>
>>>> But if the second case gets commented like this:
>>>>
>>>> case <-limiter.C:
>>>> // if len(actualBuffer) > 0 {
>>>> // buffer = actualBuffer
>>>> // } else {
>>>> // buffer = nil
>>>> // }
>>>>
>>>> It works as expected; *Output2*:
>>>>
>>>> [ info ] 2016/08/28 19:54:28 LEN_BEFORE=0
>>>>
>>>> [ info ] 2016/08/28 19:54:28 LEN=7
>>>>
>>>> [ info ] 2016/08/28 19:54:28 S00=7
>>>>
>>>> [ info ] 2016/08/28 19:54:29 LEN_BEFORE=7
>>>>
>>>> [ info ] 2016/08/28 19:54:30 LEN_BEFORE=7
>>>>
>>>> [ info ] 2016/08/28 19:54:31 LEN_BEFORE=7
>>>>
>>>> [ info ] 2016/08/28 19:54:32 LEN_BEFORE=7
>>>>
>>>> [ info ] 2016/08/28 19:54:33 LEN_BEFORE=7
>>>>
>>>> [ info ] 2016/08/28 19:54:34 LEN_BEFORE=7
>>>>
>>>> [ info ] 2016/08/28 19:54:35 LEN_BEFORE=7
>>>>
>>>> [ info ] 2016/08/28 19:54:36 LEN_BEFORE=7
>>>> ...
>>>>
>>>> Code:
>>>>
>>>> package main
>>>>
>>>>
>>>> import (
>>>> "log"
>>>> "time"
>>>>
>>>>
>>>> "github.com/comail/colog"
>>>> )
>>>>
>>>>
>>>> func status00Channeler() {
>>>> <-start
>>>>
>>>>
>>>> limiter := time.NewTicker(time.Second / maxMsgPerSec)
>>>> fetchLimiter := time.NewTicker(time.Second)
>>>>
>>>>
>>>> var buffer chan *Data
>>>> actualBuffer := make(chan *Data, maxMsgPerSec)
>>>> db, err := newDB()
>>>> if err != nil {
>>>> log.Panic(err)
>>>> }
>>>>
>>>>
>>>> FIRST:
>>>> for {
>>>> select {
>>>> case <-interrupted:
>>>> break FIRST
>>>> case <-limiter.C:
>>>> // if len(actualBuffer) > 0 {
>>>> // buffer = actualBuffer
>>>> // } else {
>>>> // buffer = nil
>>>> // }
>>>> case i := <-buffer:
>>>> select {
>>>> case status00 <- i: // will block here
>>>> case <-interrupted:
>>>> break FIRST
>>>> }
>>>> case <-fetchLimiter.C:
>>>> log.Printf("LEN_BEFORE=%d", len(actualBuffer))
>>>> if len(actualBuffer) > 0 {
>>>> continue
>>>> }
>>>>
>>>>
>>>> s00, err := db.GetIncomings()
>>>> if err != nil {
>>>> log.Println(`error:`, err)
>>>> time.Sleep(time.Second)
>>>> continue
>>>> }
>>>> if s00 == nil || len(s00) == 0 {
>>>> continue
>>>> }
>>>>
>>>>
>>>> FILL_BUFFER:
>>>> for _, v := range s00 {
>>>> select {
>>>> case actualBuffer <- v:
>>>> default:
>>>> break FILL_BUFFER
>>>> }
>>>> }
>>>>
>>>>
>>>> log.Printf("LEN=%d", len(actualBuffer))
>>>> log.Printf("S00=%d", len(s00))
>>>> }
>>>> }
>>>> }
>>>>
>>>>
>>>> func main() {
>>>> go status00Channeler()
>>>> close(start)
>>>>
>>>>
>>>> <-time.After(time.Second * 30)
>>>> }
>>>>
>>>>
>>>> var (
>>>> status00 = make(chan *Data, maxMsgPerSec)
>>>> )
>>>>
>>>>
>>>> type Data struct{}
>>>>
>>>>
>>>> const (
>>>> maxMsgPerSec = 60
>>>> )
>>>>
>>>>
>>>> func newDB() (*DB, error) {
>>>> res := new(DB)
>>>> return res, nil
>>>> }
>>>>
>>>>
>>>> func (db *DB) GetIncomings() ([]*Data, error) {
>>>> var res []*Data
>>>> res = append(res, &Data{})
>>>> res = append(res, &Data{})
>>>> res = append(res, &Data{})
>>>> res = append(res, &Data{})
>>>> res = append(res, &Data{})
>>>> res = append(res, &Data{})
>>>> res = append(res, &Data{})
>>>>
>>>>
>>>> return res, nil
>>>> }
>>>>
>>>>
>>>> type DB struct{}
>>>>
>>>>
>>>> func init() {
>>>> colog.Register()
>>>> }
>>>>
>>>>
>>>> var (
>>>> start = make(chan struct{})
>>>> interrupted = make(chan struct{}) // comes from sys interrupts
>>>> SIGINT, SIGTERM, etc
>>>> )
>>>>
>>>>
>>>> --
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>>>> Groups "golang-nuts" group.
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>>>>
>>> --
>>>
>>> -j
>>>
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