>Talking about the select() or poll() functions from the C library which
evidently were an inspiration for the Go select statement
Go select is more similar to alt() than select() or poll()
On Friday, May 4, 2018 at 7:24:56 AM UTC-7, Andriy Pylypenko wrote:
>
> Hi,
>
> I have a scenario which I haven't found a way to implement with the Go
> channels and select statement while it's no problem to do it with the
> select()/poll() functions. The scenario is as follows.
>
> Let me use a Go-like pseudo-code to demonstrate the idea. There is a
> source of a work items which are processed by several goroutines. Here is
> the source procedure:
>
> work_ch := make(chan *WorkItem)
>
> for {
> work_ch <- NewWorkItem()
> }
>
> And here is the worker thread:
>
> for {
> wi := <-work_ch
> self.do_the_work(wi)
> }
>
> Now I need to suspend the work. I stop supplying the work items and want
> to make sure the worker goroutines are done with the work. The source
> procedure becomes something like this:
>
> for {
> if suspend_requested {
> for _, worker := range workers {
> worker.idle_request <- true
> }
> for _, worker := range workers {
> <-worker.idle_response
> }
> report_suspend_is_success()
> wait_until_unsuspended()
> }
> work_ch <- NewWorkItem()
> }
>
> And I want to modify the worker thread like this:
>
> for {
> select {
> case wi := <- work_ch:
> self.do_the_work(wi)
> case <-self.idle_request:
> self.idle_response <- true
> }
> }
>
> However this last snippet of code does not work because the cases within
> the select statement are randomly chosen when both channels are ready so I
> have no guarantee that the first case is executed first.
>
> Talking about the select() or poll() functions from the C library which
> evidently were an inspiration for the Go select statement, there is no
> problem with the described approach. It's because the select() function
> returns a complete information about the state of all the monitored
> descriptors and allows the programmer to decide what he wants to read or
> write and in which order, based on readiness of every descriptor.
>
> I think it would be a great idea to have some function similar to
> select()/poll() but working with the Go channels.
>
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