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vibe.d requestHTTP in static this causes infinite loop?
May 19, 2022
Vijay Nayar
May 20, 2022
Ali Çehreli
May 20, 2022
bauss
May 20, 2022
Vijay Nayar
May 19, 2022
Gravatar of Vijay NayarPosted by Vijay NayarReply
Vijay Nayar
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I've encountered an unusual behavior that I have no good explanation for. Consider the following code example:

import vibe.core.log : logInfo;
import vibe.http.client : requestHTTP, HTTPClientRequest, HTTPClientResponse;
import vibe.http.common : HTTPMethod;
import vibe.stream.operations : readAllUTF8;

void doThing() {
  requestHTTP("http://example.com/",
      (scope HTTPClientRequest req) {
        logInfo("Setting request method.");
        req.method = HTTPMethod.GET;
      },
      (scope HTTPClientResponse res) {
        logInfo("Log point 1");
        string data = res.bodyReader.readAllUTF8();
        logInfo("Log point 2: %s", data);
      });
}

static this() {
  logInfo("--- static this() ---");
  doThing();
}

void main(string[] args) {
  logInfo("--- main() ---");
  doThing();
}

The output of this program is actually an infinite loop with output of the form:

[Eventcore DNS Lookup(----) INF] --- static this() ---
[Eventcore DNS Lookup(----) INF] --- static this() ---

If I remove the call from static this(), then the web call works as normal. Any idea why calling vibe.d's requestHTTP function inside of a module's static construction would cause an infinite loop?

May 19, 2022
Gravatar of Ali ÇehreliPosted by Ali Çehreli
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Ali Çehreli
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On 5/19/22 16:44, Vijay Nayar wrote:

> If I remove the call from `static this()`, then the web call works as
> normal. Any idea why calling vibe.d's `requestHTTP` function inside of a
> module's static construction would cause an infinite loop?

I am not experienced with vibe.d.

'static this' is executed per thread. If requestHTTP starts a new thread, then I can see how you would be in an infinite loop. I wonder whether it should be 'shared static this' (which is executed once per program, not per thread).

Ali
May 20, 2022
Gravatar of baussPosted by bauss
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bauss
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On Friday, 20 May 2022 at 01:41:59 UTC, Ali Çehreli wrote:
> On 5/19/22 16:44, Vijay Nayar wrote:
>
> > If I remove the call from `static this()`, then the web call
> works as
> > normal. Any idea why calling vibe.d's `requestHTTP` function
> inside of a
> > module's static construction would cause an infinite loop?
>
> I am not experienced with vibe.d.
>
> 'static this' is executed per thread. If requestHTTP starts a new thread, then I can see how you would be in an infinite loop. I wonder whether it should be 'shared static this' (which is executed once per program, not per thread).
>
> Ali

Static constructor shouldn't be there at all in this case, since it's not constructing anything.

He shouldn't really use anything but main in this case.
May 20, 2022
Gravatar of Vijay NayarPosted by Vijay Nayar
in reply to Ali Çehreli		Reply
Vijay Nayar
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Posted in reply to Ali Çehreli


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On Friday, 20 May 2022 at 01:41:59 UTC, Ali Çehreli wrote:
> On 5/19/22 16:44, Vijay Nayar wrote:
>
> > If I remove the call from `static this()`, then the web call
> works as
> > normal. Any idea why calling vibe.d's `requestHTTP` function
> inside of a
> > module's static construction would cause an infinite loop?
>
> I am not experienced with vibe.d.
>
> 'static this' is executed per thread. If requestHTTP starts a new thread, then I can see how you would be in an infinite loop. I wonder whether it should be 'shared static this' (which is executed once per program, not per thread).
>
> Ali

Very clever, you were exactly right. I had not thought of that, but that is indeed what was happening.