CLI: Handle stdin stream if it's a regular file

[dcantah]

readabilityHandler is a bit crummy if it's a regular file. This just writes our own loop and exits and shuts down the write end of the pipe if we get to the end of the file.

[dcantah]

@jglogan This hopefully should get piping a file in working, will test tomorrow. We'll need both this and bump of containerization that has the closing stdin work however.

[jglogan]

@dcantah

Can you check to see if terminal I/O works for you in this branch with:

container run -it --rm alpine:latest sh

[dcantah]

@jglogan It doesn't, it's why it's in draft right now. FileHandle.read(upToCount reads until EOF by default, so I'll need to write my own read(2) loop (and make stdin nonblocking).

[dcantah]

@jglogan tty fixed, and I can confirm we close the relay on eof for regular files. What's the avenue for testing against containerization main these days? It seem make init-block returns the version as unspecified

[dcantah]

Note: I've just copied a smaller portion of this same type we have for vminitd here. I'll see if it makes sense to make that public over in CZ, and we can just use directly.

[jglogan]

What's the avenue for testing against containerization main these days?

What's missing from the build documentation is that you need to set up the default init image as vminit:latest, and then restart everything so that both the CLI and the API server pick up the correct default init image.

make all install
defaults write com.apple.container.defaults image.init vminit:latest
container system stop
container system start
container run -d --rm --name test python:slim python3 -m http.server --bind 0.0.0.0 8000
echo hello | container exec -t exec -i test cp /dev/stdin /tmp/hello.txt

FWIW I'm seeing that this seems to suffice for the exec test:

diff --git a/Sources/CLI/RunCommand.swift b/Sources/CLI/RunCommand.swift
index 9a7f0d7..1d3f0cc 100644
--- a/Sources/CLI/RunCommand.swift
+++ b/Sources/CLI/RunCommand.swift
@@ -218,6 +218,7 @@ struct ProcessIO {
                     let data = handle.availableData
                     if data.isEmpty {
                         pin.readabilityHandler = nil
+                        try? stdin.fileHandleForWriting.close()
                         return
                     }
                     try! stdin.fileHandleForWriting.write(contentsOf: data)

That we fetch the init filesystem in the client at https://github.com/apple/container/blob/main/Sources/ContainerClient/Utility.swift#L113, and then again when creating the container in the API server https://github.com/apple/container/blob/main/Sources/APIServer/Containers/ContainersService.swift#L165 is curious.

[jglogan]

mainly readability nits