Mill stuck when used on WSL 2

[Iltotore]

Mill version: 0.10.9 (also tested in 0.10.4+)
OS: WSL Debian GNU/Linux 11 (bullseye) on Windows 10 x86_64
Java: openjdk version "17.0.4" 2022-07-19

Using Mill on WSL results in this error:

Exception in thread "main" org.newsclub.net.unix.InvalidArgumentSocketException: Invalid argument
        at org.newsclub.net.unix.NativeUnixSocket.bind(Native Method)
        at org.newsclub.net.unix.AFSocketImpl.bind(AFSocketImpl.java:335)
        at org.newsclub.net.unix.AFServerSocket.bind(AFServerSocket.java:257)
        at java.base/java.net.ServerSocket.bind(ServerSocket.java:342)
        at org.newsclub.net.unix.AFServerSocket.bindOn(AFServerSocket.java:176)
        at org.newsclub.net.unix.AFUNIXServerSocket.bindOn(AFUNIXServerSocket.java:87)
        at mill.main.Server.$anonfun$run$2(MillServerMain.scala:103)
        at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
        at mill.main.Server$.lockBlock(MillServerMain.scala:227)
        at mill.main.Server.$anonfun$run$1(MillServerMain.scala:98)
        at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
        at mill.main.Server$.tryLockBlock(MillServerMain.scala:235)
        at mill.main.Server.run(MillServerMain.scala:95)
        at mill.main.MillServerMain$.main(MillServerMain.scala:53)
        at mill.main.MillServerMain.main(MillServerMain.scala)

followed by a hanging. Relaunching Mill hangs without the above error but it prints again if I delete the out/mill directory.

It doesn't seem to be related to #874

[sake92]

Seems like WSL 2 doesn't support Unix sockets.
https://stackoverflow.com/a/73067921/4496364

You'll have to use no-server mode mill -i, or try native Windows.

[lefou]

Please note that I just discovered that the bundled mill script of 0.10.9 release has some issues with -i or --no-server mode. See #2123 (comment).

Let's see if we can detect a running WSL 2 from a running Mill process, so that we can always fall back to --no-server mode.

[Iltotore]

I tested with both wrapper and "normal" Mill command. Still no success. I tested with annd without -i. I don't know if --no-server would change anything but I will test it once I get to home.

[sake92]

I tested it on my Windows 11:

sake@DESKTOP-ILD4SJJ:/mnt/c/projects/stuff/millll/jah4$ ./mill-0.10.11-assembly.bat -i jah4.run
Compiling /mnt/c/projects/stuff/millll/jah4/build.sc
[13/46] jah4.unmanagedClasspath
[33/46] jah4.compile
Compiling compiler interface...
[info] compiling 1 Scala source to /mnt/c/projects/stuff/millll/jah4/out/jah4/compile.dest/classes ...
[info] done compiling
[46/46] jah4.run
Hello world!


sake@DESKTOP-ILD4SJJ:/mnt/c/projects/stuff/millll/jah4$ ./mill-0.10.11-assembly.bat  jah4.run
Exception in thread "main"
org.newsclub.net.unix.AddressUnavailableSocketException: Operation not supported
        at org.newsclub.net.unix.NativeUnixSocket.bind(Native Method)
        at org.newsclub.net.unix.AFSocketImpl.bind(AFSocketImpl.java:335)
        at org.newsclub.net.unix.AFServerSocket.bind(AFServerSocket.java:257)
        at java.net.ServerSocket.bind(ServerSocket.java:344)
        at org.newsclub.net.unix.AFServerSocket.bindOn(AFServerSocket.java:176)
        at org.newsclub.net.unix.AFUNIXServerSocket.bindOn(AFUNIXServerSocket.java:87)
        at mill.main.Server.$anonfun$run$2(MillServerMain.scala:103)
        at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
        at mill.main.Server$.lockBlock(MillServerMain.scala:227)
        at mill.main.Server.$anonfun$run$1(MillServerMain.scala:98)
        at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.scala:18)
        at mill.main.Server$.tryLockBlock(MillServerMain.scala:235)
        at mill.main.Server.run(MillServerMain.scala:95)
        at mill.main.MillServerMain$.main(MillServerMain.scala:53)
        at mill.main.MillServerMain.main(MillServerMain.scala)
Exception in thread "main" java.lang.Exception: Failed to connect to server
        at mill.main.client.MillClientMain.run(MillClientMain.java:195)
        at mill.main.client.MillClientMain.main0(MillClientMain.java:121)
        at mill.main.client.MillClientMain.main(MillClientMain.java:71)
Caused by: java.net.SocketException: No such file or directory
        at org.newsclub.net.unix.NativeUnixSocket.connect(Native Method)
        at org.newsclub.net.unix.AFSocketImpl.connect0(AFSocketImpl.java:392)
        at org.newsclub.net.unix.AFSocket.connect0(AFSocket.java:267)
        at org.newsclub.net.unix.AFSocket.connect(AFSocket.java:236)
        at org.newsclub.net.unix.AFSocket.connect(AFSocket.java:231)
        at org.newsclub.net.unix.AFSocket.connectTo(AFSocket.java:179)
        at org.newsclub.net.unix.AFUNIXSocket.connectTo(AFUNIXSocket.java:109)
        at mill.main.client.MillClientMain.run(MillClientMain.java:187)
        ... 2 more

Works as expected. In the -i mode does what it's told.
Client-server doesn't work since WSL doesn't support unix sockets yet.

[lefou]

If you can tell me, how I can safely detect a WSL 2 environment, then we can safeguard to always use the non-server mode on WSL 2.

[andrelfpinto]

scala> System.getProperty("os.version")
val res2: String = 5.15.90.1-microsoft-standard-WSL2

works if it is not a custom kernel.

I guess this option is not that usual. In this case, one can always run it with --no-server.

[lefou]

I just merged #2901 to always run in no-server mode on WSL.