Windows compatibility?

[moufmouf]

Hi guys,

I've been trying to use reactphp/child-process on Windows and I've had hard times having it to work.
I traced the problem back to a bug in PHP:

https://bugs.php.net/bug.php?id=51800

The bug has been solved, at least in recent PHP versions.

To sum it up:

I have an application that uses child-process and that works flawlessly on Linux.
On Windows, reactphp/child-process does not work with PHP 5.5.12. The PHP process stalls and nothing is happening (just like in the PHP bug)

It seems to work with PHP 5.6.6, although I'm having some strange behaviour (I'm facing locks of several seconds, then the application starts again...)

I've tried to run the unit tests of the master branch and many are failing in Windows. I'm not sure if those are supposed to work. Did you have any of those unit tests running on Windows? If yes, what version of PHP did you use?

Do you need some help working on that compatibility or is there something I missed?

[clue]

I've been trying to use reactphp/child-process on Windows and I've had hard times having it to work.

Same here, unfortunately I'm having to give up on this for now..
I've got this to work to some degree, however finding some test cases that still fail wasn't too difficult.
(I'll try to file a PR to provide these in the upcoming days)

Current status (afaict):

• PR Windows test suite compatibility #13 (originally Fixing unit tests for Windows #10) aims to improve the test suite for Windows
• PR Windows fix #11 aims to work around Windows' limitations by using file handles instead of process pipes.
  This is a significant improvement, however, this also introduces several other issues (writing to disk, different buffering behavior, possible privacy leak, degraded performance, stale files etc.)
• I've looked into using stream_socket_pair() to no avail (works just fine on non-Windows)
• I've looked into using a TCP/IP client/server sockets to no avail (works just fine on non-Windows)
• I've looked into using names pipes to no avail

Has anybody ever reached a state in which this can be considered "compatible"? If so, which version / OS?

[clue]

Afaict the compatibility issues are cause by two independent issues:

stream_set_blocking() does not work with pipes opened with proc_open() (https://bugs.php.net/bug.php?id=47918). This appears to be because Windows' process pipes do not support async operation, so this is unlikely to caused (or ever fixed) by PHP.

stream_select() (and family) always reports the pipes as readable even when no data is available. This will cause the Stream class to always invoke a fread() on the pipes.

• Adding the above blocking stream behavior, this will thus block the event look.
• This appears to be addressed in several commits in different PHP versions (not sure which exactly).

I could not reproduce any blocking behavior on proc_open() itself (https://bugs.php.net/bug.php?id=51800). I'm not sure if this issue ever did exist in the first place or if this could boil down to the above issue in fact.

[clue]

• PR Windows fix #11 aims to work around Windows' limitations by using file handles instead of process pipes.
  This is a significant improvement, however, this also introduces several other issues (writing to disk, different buffering behavior, possible privacy leak, degraded performance, stale files etc.)

…

I've looked into using stream_socket_pair() to no avail (works just fine on non-Windows)

Potentially, connected sockets could work around these limitations. Has anybody else tried using connected sockets instead of file descriptors?

FWIW: Here's my attempt (which does not work on Windows, but does work on non-Windows systems): https://github.com/reactphp/child-process/compare/master...clue-labs:sockets?expand=1

[joshdifabio]

• I've looked into using names pipes to no avail – @clue

How far did you get with that? Did you find a way to create a named pipe on Windows?

[clue]

• I've looked into using names pipes to no avail – @clue

How far did you get with that? Did you find a way to create a named pipe on Windows? – @joshdifabio

Unfortunately not very far at all, I've toyed around with this idea to no avail.

[clue]

stream_set_blocking() does not work with pipes opened with proc_open() (https://bugs.php.net/bug.php?id=47918). This appears to be because Windows' process pipes do not support async operation, so this is unlikely to caused (or ever fixed) by PHP.

See also my suggested PR reactphp/stream#46

With this change applied, the Process class would throw a RuntimeException on Windows, because it can not set the streams to be non-blocking.

IMO this does make sense, because we can't guarantee proper execution otherwise anyway.

Once this change is in, we should look into adding an option to start child processes without any STDOUT/STDIN streams, which sometimes makes sense on all platforms and should also work on Windows.

[kelunik]

The hardest thing is probably getting the correct exit code on Windows. It just doesn't seem to work.

[clue]

@kelunik What issue are you running in to, can you provide a gist to reproduce this?

[clue]

Let's recap what works and what doesn't:

• Executing child processes ✔️
• Writing to STDIN and reading from STDOUT: might block ❌
• Returning exit-code: unknown ❓