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Date: Sat, 25 Jan 2020 17:03:25 -0500
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To: Rowan Tommins <rowan.collins@gmail.com>,
 Robert Hickman <robehickman@gmail.com>
Subject: Re: [PHP-DEV] Add viable long running execution model to php 8
From: mike@newclarity.net (Mike Schinkel)

On Jan 25, 2020, at 3:44 PM, Rowan Tommins <rowan.collins@gmail.com> =
wrote:
>=20
> On 25/01/2020 18:51, Robert Hickman wrote:
>=20
>> Yes that is what I was thinking, for example there is a userspace =
implementation
>> 'Swoole' that works in the following way, ReactPHP is similar =
although I won't
>> include that example as well.
>=20
>=20
> So trying to get concrete: the first "official" component we'd need =
would be an outer event loop, mapping requests and responses to the =
parameter and return values of userland callbacks. In principle, not too =
difficult, although I'm sure there are plenty of devils in the details.
>=20
>=20
>> In my mind right now, everything should be shareable within a single =
process,
>> as one could do in the Swoole example above, nothing stopping you =
defining a
>> global in that script that could cache data in-process.
>>=20
>> NodeJS, Python (wsgi) and others work fine using this model and allow =
sharing
>> of data within the same process. Trying to limit it to only some =
types of things
>> would be more complex as each type of thing would end up having a =
different
>> programmatic interface.
>=20
>=20
> I may be wrong, but I think this is where it gets complicated. It's =
not that we'd want to deliberately have different things have different =
behaviour between requests, it's just that we've got a bunch of existing =
stuff built on the assumptions of the current architecture.
>=20
> In a single-threaded event loop, you want as much as possible to be =
asynchronous, which is why both Swoole and React have a lot of modules =
for things like network requests, file I/O, databases, and general =
asynchronous programming.
>=20
> Other things just wouldn't exist if PHP hadn't been modelled as shared =
nothing from the beginning. Would set_time_limit() still be global, and =
abort the server after a fixed number of seconds? Or would it configure =
the event loop somehow?
>=20
> I think there'd need to be at least a roadmap for sorting out those =
questions in the official distribution before it felt like a properly =
supported part of the language.

I'm not following the discussion 100% =E2=80=93 more like 85% =E2=80=94 =
but it seems like what we might be saying is the need for a user-land =
implementation of a long-running PHP request, one that does not timeout?

If that is the case, could we consider allowing a PHP page to opt-in to =
no timeout?  These types of requests could then handle web sockets, etc.

Then we could look to prior art with GoLang channels where they =
"Communicate to share memory" and do not "Share memory to communicate."  =
IOW, add an API that allows a regular PHP page to communicate with a =
long-running page.  This would decouple and allow for better testing, =
and hopefully fewer hard to track down bugs.

Further, I would suggest the long running requests not be able to =
generate output except when the ini setting display_errors is true to =
ensure they are only used for communicating with regular "shared =
nothing" pages and not used in place of shared-nothing pages?

Would this not be a workable approach?

-Mike=