vibe.d-lite v0.1.0 powered by photon

[Sönke Ludwig]

Am 19.09.25 um 18:29 schrieb Dmitry Olshansky:
>> Shouldn't it still be possible to set an "interrupted" flag somewhere 
>> and let only the vibe-core-lite APIs throw? Low level C functions 
>> should of course stay unaffected.
> 
> Since vibe-core-light depends on syscalls this would mean creating a 
> separate set of API for vibe-core-light which is not something I’d like 
> to do.
>>
>> It's more of a timeout pattern that I've seen multiple times, there 
>> are certainly multiple (better) alternatives, but if compatibility 
>> with existing code is the goal then this would still be important.
> 
> I guess, again most likely I’d need to create API specifically for vibe. 
> Also that would mean interrupt becomes part of photon but only works 
> when certain APIs are used. This is bad.

So you don't support timeouts when waiting for an event at all? 
Otherwise I don't see why a separate API would be required, this should 
be implementable with plain Posix APIs within vibe-core-lite itself.

>>>
>>> I on the other hand imagine that it’s not. In year 2025 not utilizing 
>>> all of available cores is shameful. The fact that I had to dig around 
>>> to find how vibe.d is supposed to run on multiple cores is telling.
>>
>> Telling in what way?
> 
> That running single threaded is the intended model.

Obviously this is wrong, though.

>> It's really quite simple, you can use plain D threads as normal, or 
>> you can use task pools, either explicitly, or through the default 
>> worker task pool using `runWorkerTask` or `runWorkerTaskDist`. (Then 
>> there are also higher level concepts, such as async, performInWorker 
>> or parallel(Unordered)Map)
> 
> This does little to the most important case - handling requests in 
> parallel. Yeah there are pool and such for cases where going parallel 
> inside of a single request makes sense.


```
runWorkerTaskDist({
	HTTPServerSettings settings;
	settings.options |= HTTPServerOption.reusePort;
	listenHTTP(settings);
});
```

> 
>> Not everything is CPU bound and using threads "just because" doesn't 
>> make sense either. This is especially true, because of low level race 
>> conditions that require special care. D's shared/immutable helps with 
>> that, but that also means that your whole application suddenly needs 
>> to use shared/immutable when passing data between tasks.
> 
> I’m dying to know which application not being cpu bound still needs to 
> pass data between tasks that are all running on a single thread.

Anything client side involving a user interface has plenty of 
opportunities for employing secondary tasks or long-running sparsely 
updated state logic that are not CPU bound. Most of the time is spent 
idle there. Specific computations on the other hand can of course still 
be handed off to other threads.

>> But TLS variables are always "globals" in the sense that they outlive 
>> the scope that accesses them. A modification in one thread would 
>> obviously not be visible in another thread, meaning that you may or 
>> may not have a semantic connection when you access such a library 
>> sequentially from multiple tasks.
>>
>> And then there are said libraries that are not thread-safe at all, or 
>> are bound to the thread where you initialize them. Or handles returned 
>> from a library may be bound to the thread that created them. Dealing 
>> with all of this just becomes needlessly complicated and error-prone, 
>> especially if CPU cycles are not a concern.
> 
> TLS is fine for using not thread safe library - just make sure you 
> initialize it for all threads. I do not switch or otherwise play dirty 
> tricks with TLS.

The problem is that for example you might have a handle that was created 
in thread A and is not valid in thread B, or you set a state in thread A 
and thread B doesn't see that state. This would mean that you are 
limited to a single task for the complete library interaction.

>> By robbing the user the control over where a task spawns, you are also 
>> forcing synchronization everywhere, which can quickly become more 
>> expensive than any benefits you would gain from using multiple threads.
> 
> Either of default kind of rob user of control of where the task spawns. 
> Which is sensible a user shouldn’t really care.

This doesn't make sense, in the original vibe-core, you can simply 
choose between spawning in the same thread or in "any" thread. 
`shared`/`immutable` is correctly enforced in the latter case to avoid 
unintended data sharing.

>> Finally, in the case of web applications, in my opinion the better 
>> approach for using multiple CPU cores is *usually* by running multiple 
>> *processes* in parallel, as opposed to multiple threads within a 
>> single process. Of course, every application is different and there is 
>> no one-size-fits-all approach.
> 
> There we differ, not only load balancing is simpler within a single 
> application but also processes are more expansive. Current D GC 
> situation kind of sucks on multithreaded workloads but that is the only 
> reason to go multiprocess IMHO.

The GC/malloc is the main reason why this is mostly false in practice, 
but it extends to any central contention source within the process - 
yes, often you can avoid that, but often that takes a lot of extra work 
and processes sidestep that issue in the first place.

Also, in the usual case where the threads don't have to communicate with 
each other (apart from memory allocation synchronization), a separate 
process per core isn't any slower - except maybe when hyper-threading is 
in play, but whether that helps or hurts performance always depends on 
the concrete workload. Separate process also have the advantage of being 
more robust and enabling seamless restarts and updates of the 
executable. And they facilitate an application design that lends itself 
to scaling across multiple machines.