Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:126431
Precedence: bulk
MIME-Version: 1.0
References: <CAMW7n8CcNuttyxhtDeG1apHFVjU_9sKAhf0RG890b82Q1AnJpw@mail.gmail.com>
 <24becc76-b67f-4805-b33b-cd4f9f6d0b30@scriptfusion.com>
In-Reply-To: <24becc76-b67f-4805-b33b-cd4f9f6d0b30@scriptfusion.com>
Date: Mon, 17 Feb 2025 19:29:34 +0200
Message-ID: <CAMW7n8DhYKngXR-xHL_sS5+Zr+wS2U1Zunj0HDzaM08Yx=i9WA@mail.gmail.com>
Subject: Re: [PHP-DEV] PHP True Async
To: Bilge <bilge@scriptfusion.com>
Cc: internals@lists.php.net
Content-Type: multipart/alternative; boundary="000000000000d60838062e59de80"
From: edmond.ht@gmail.com (Edmond Dantes)

--000000000000d60838062e59de80
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

Hello Bilge!

> Is it really necessary to have all these `Async\launchScheduler();`
calls? Why can't the scheduler always be running, the same as it is in
JavaScript or any other async language? Even (userland) Revolt does not
require the event loop to be manually started.

*Short answer:* This implementation is simpler =E2=80=94 not so much in ter=
ms of
code size but in terms of reducing =D1=81onfusion. And we achieve a consist=
ent
state when asynchronous code runs within a Fiber, rather than having a
situation where we are in a Fiber here but not there.

For example, consider how the Fiber switching mechanism works in PHP. If
FiberB is launched from FiberA, FiberB can only return to FiberA.
Consequently, if the Scheduler component is placed inside a Fiber, the code
must track the "direction" of switching.

Running the Scheduler in the "zero" Fiber results in the simplest possible
switching logic. It also defines a clear point where exceptions can be
thrown.

One might argue that no other language does it this way. But then, no other
language has Fiber as a low-level tool (except C). From this perspective,
explicit activation of the Scheduler aligns with Fiber as a low-level
construct.

Can this be avoided? Yes, but such alternative approaches often rely
on *implicit
behavior*. And implicit behavior tends to break things.

Of course, we could start the code inside a Fiber to initialize the
Scheduler and hide the implementation, but again, that's not always
necessary or useful for everyone.

Ed.

--000000000000d60838062e59de80
Content-Type: text/html; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable

<div dir=3D"ltr">Hello Bilge!<div><br></div><div>&gt; Is it really necessar=
y to have all these `Async\launchScheduler();` calls? Why can&#39;t the sch=
eduler always be running, the same as it is in JavaScript or any other asyn=
c language? Even (userland) Revolt does not require the event loop to be ma=
nually started.</div><div><strong><br></strong></div><div><strong>Short ans=
wer:</strong> This implementation is simpler =E2=80=94 not so much in terms=
 of code size but in terms of reducing=20

=D1=81onfusion. And we achieve a consistent state when asynchronous code ru=
ns within a Fiber, rather than having a situation where we are in a Fiber h=
ere but not there.

</div><div><p>For example, consider how the Fiber switching mechanism works=
 in PHP. If FiberB is launched from FiberA, FiberB can only return to Fiber=
A. Consequently, if the Scheduler component is placed inside a Fiber, the c=
ode must track the &quot;direction&quot; of switching.</p><p>Running the Sc=
heduler in the &quot;zero&quot; Fiber results in the simplest possible swit=
ching logic. It also defines a clear point where exceptions can be thrown.<=
/p><p>One might argue that no other language does it this way. But then, no=
 other language has Fiber as a low-level tool (except C). From this perspec=
tive, explicit activation of the Scheduler aligns with Fiber as a low-level=
 construct.</p><p>Can this be avoided? Yes, but such alternative approaches=
 often rely on <b>implicit behavior</b>. And implicit behavior tends to bre=
ak things.</p><p>Of course, we could start the code inside a Fiber to initi=
alize the Scheduler and hide the implementation, but again, that&#39;s not =
always necessary or useful for everyone.</p><p>Ed.</p></div></div>

--000000000000d60838062e59de80--