I have the following that is supposed to pull and store info from a server every five minutes. It works if I move the body of deviceDownloader into main(). However when I try to spawn it in another thread it runs the function and then ends once it's done, like it's ignoring the while(true). I tried with std.parallelism, core.thread, vibe.d's concurrency library, but get the same result every time. Any idea how to better accomplish this?


import std.net.curl;
import device;
import std.datetime.systime;
impor std.concurrency;

void deviceDownloader()
{
    auto APIServer = HTTP();
    APIServer.addRequestHeader("X-Auth-Token:", AuthToken);
    APIServer.onProgress = delegate int(size_t dl, size_t dln, size_t ul, size_t uln)
    {
        if (dl != 0)
            write("Progress: downloaded ", dln, " of ", dl, "\r");

        return 0;
    };

    while (true)
    {
        auto currentTime = Clock.currTime;
        if (currentTime.minute % 5 == 0 && currentTime.second == 0)
            retrieveDevices(URL, APIServer); // info retrieved and stored here
    }
}

void main()
{
    spawn(&deviceDownloader);
}

On Friday, 19 January 2018 at 17:05:44 UTC, Chris M. wrote:
> However when I try to spawn it in another thread it runs the function and then ends once it's done, like it's ignoring the while(true).


It is probably terminating the child threads when the main one ends. Might help to have the main wait until the child dies too.

But why are you putting it in a thread anyway? If the main is doing nothing than just waiting, might as well just keep the logic in there.

On Friday, 19 January 2018 at 17:17:28 UTC, Adam D. Ruppe wrote:
> On Friday, 19 January 2018 at 17:05:44 UTC, Chris M. wrote:
>> However when I try to spawn it in another thread it runs the function and then ends once it's done, like it's ignoring the while(true).
>
>
> It is probably terminating the child threads when the main one ends. Might help to have the main wait until the child dies too.

I tried putting an infinite loop inside main() as well, didn't seem to help. I'm guessing there's probably a better way to make the main thread wait? I'm pretty new to threads and whatnot.

> But why are you putting it in a thread anyway? If the main is doing nothing than just waiting, might as well just keep the logic in there.

It'll be doing other things, this is just the first thing I've implemented.

On 01/19/2018 09:46 AM, Chris M. wrote:

> I tried putting an infinite loop inside main() as well, didn't seem to
> help.

Another reason is an exception thrown in the child thread. If the exception is not caught, it will terminate the child thread and the main will not know anything about it. I have something about that here:


http://ddili.org/ders/d.en/concurrency.html#ix_concurrency.exception,%20concurrency

> I'm guessing there's probably a better way to make the main thread
> wait?

std.core.thread_joinAll is a way but you would want to tell the other thread to terminate first.

  https://dlang.org/phobos/core_thread.html#.thread_joinAll

So, instead of while(true), try while(someCondition). In that case the main thread sets the condition e.g. by sending a message and then joins.

Ali

On Friday, 19 January 2018 at 18:18:31 UTC, Ali Çehreli wrote:
> On 01/19/2018 09:46 AM, Chris M. wrote:
>
> > I tried putting an infinite loop inside main() as well,
> didn't seem to
> > help.
>
> Another reason is an exception thrown in the child thread. If the exception is not caught, it will terminate the child thread and the main will not know anything about it. I have something about that here:
>
>
> http://ddili.org/ders/d.en/concurrency.html#ix_concurrency.exception,%20concurrency
>
> > I'm guessing there's probably a better way to make the main
> thread
> > wait?
>
> std.core.thread_joinAll is a way but you would want to tell the other thread to terminate first.
>
>   https://dlang.org/phobos/core_thread.html#.thread_joinAll
>
> So, instead of while(true), try while(someCondition). In that case the main thread sets the condition e.g. by sending a message and then joins.
>
> Ali

I'm not sure what's going on. I've tried all sorts of things from your link, it just runs the function once and exits every time. There aren't any exceptions being thrown from the thread.

That robot example is basically exactly what I'm doing, and yet even that doesn't seem to resolve it.

On Friday, 19 January 2018 at 20:35:14 UTC, Chris M. wrote:
> On Friday, 19 January 2018 at 18:18:31 UTC, Ali Çehreli wrote:
>> On 01/19/2018 09:46 AM, Chris M. wrote:
>>
>> > I tried putting an infinite loop inside main() as well,
>> didn't seem to
>> > help.
>>
>> Another reason is an exception thrown in the child thread. If the exception is not caught, it will terminate the child thread and the main will not know anything about it. I have something about that here:
>>
>>
>> http://ddili.org/ders/d.en/concurrency.html#ix_concurrency.exception,%20concurrency
>>
>> > I'm guessing there's probably a better way to make the main
>> thread
>> > wait?
>>
>> std.core.thread_joinAll is a way but you would want to tell the other thread to terminate first.
>>
>>   https://dlang.org/phobos/core_thread.html#.thread_joinAll
>>
>> So, instead of while(true), try while(someCondition). In that case the main thread sets the condition e.g. by sending a message and then joins.
>>
>> Ali
>
> I'm not sure what's going on. I've tried all sorts of things from your link, it just runs the function once and exits every time. There aren't any exceptions being thrown from the thread.
>
> That robot example is basically exactly what I'm doing, and yet even that doesn't seem to resolve it.

What I tried

import std.net.curl;
import device;
import std.datetime.systime;
impor std.concurrency;

void deviceDownloader()
{
    auto APIServer = HTTP();
    APIServer.addRequestHeader("X-Auth-Token:", AuthToken);
    APIServer.onProgress = delegate int(size_t dl, size_t dln, size_t ul, size_t uln)
    {
        if (dl != 0)
            write("Progress: downloaded ", dln, " of ", dl, "\r");

        return 0;
    };

    while (true)
    {
        auto currentTime = Clock.currTime;
        if (currentTime.minute % 5 == 0 && currentTime.second == 0)
            retrieveDevices(URL, APIServer); // info retrieved and stored here
        ownerTid.send("tmp");
    }
}

void main()
{
    spawn(&deviceDownloader);

    while (true)
    {
        auto msg = receiveOnly!string();
    }
}

On 1/19/18 12:05 PM, Chris M. wrote:
> I have the following that is supposed to pull and store info from a server every five minutes. It works if I move the body of deviceDownloader into main(). However when I try to spawn it in another thread it runs the function and then ends once it's done, like it's ignoring the while(true). I tried with std.parallelism, core.thread, vibe.d's concurrency library, but get the same result every time. Any idea how to better accomplish this?
> 
> 
> import std.net.curl;
> import device;
> import std.datetime.systime;
> impor std.concurrency;
> 
> void deviceDownloader()
> {
>      auto APIServer = HTTP();
>      APIServer.addRequestHeader("X-Auth-Token:", AuthToken);
>      APIServer.onProgress = delegate int(size_t dl, size_t dln, size_t ul, size_t uln)
>      {
>          if (dl != 0)
>              write("Progress: downloaded ", dln, " of ", dl, "\r");

What is this call doing? You aren't importing std.stdio, so it can't be D's normal write call.

-Steve

On Friday, 19 January 2018 at 20:43:18 UTC, Steven Schveighoffer wrote:
> On 1/19/18 12:05 PM, Chris M. wrote:
>> [...]
>
> What is this call doing? You aren't importing std.stdio, so it can't be D's normal write call.
>
> -Steve

It is, left out the import on accident.

I commented out the call to retrieveDevices, and now it's working, so at least I'm zoning in a bit. Appreciate all the help so far though.

On 1/19/18 3:54 PM, Chris M. wrote:
> On Friday, 19 January 2018 at 20:43:18 UTC, Steven Schveighoffer wrote:
>> On 1/19/18 12:05 PM, Chris M. wrote:
>>> [...]
>>
>> What is this call doing? You aren't importing std.stdio, so it can't be D's normal write call.
>>
>> -Steve
> 
> It is, left out the import on accident.
> 
> I commented out the call to retrieveDevices, and now it's working, so at least I'm zoning in a bit. Appreciate all the help so far though.

Hm... noticed you missed a 't' here as well:

impor std.concurrency;

It helps if you post actual working (or reproducing in any case) code. I've seen so many posts on this forum where people re-type their code in the post instead of copy-pasting, and then inadvertently leave out a major hint leading to the actual issue :)

-Steve

On 01/19/2018 12:40 PM, Chris M. wrote:
> it just runs the function once and exits every time.

I would still put the following try+catch block around the whole logic:

void deviceDownloader()
{
    try {
        // ... existing contents of the function ...
    } catch (Exception exc) {
        writeln("Error: ", exc.msg);
    } catch (Error err) {
        writeln("Unrecoverable error: ", err.msg);
    }
}

Another thing to use it to start the program under a debugger and look at how many threads it has. If the program is called "deneme", on the console:

 gdb deneme

Then, inside gdb:

run
Ctrl-C
info threads

That command lists two threads for me.

Ali