gorun | automatically restart APP when go files | Continuous Deployment library

First a quick disclaimer that I haven't done this binfmt trick to run go scripts. I suppose it might work, but I just use go run when I want to run something on the fly.

There's a lot to unpack in this. Container isolation runs an application with a shared kernel in an isolated environment. The namespaces, cgroups, and security settings are designed to prevent one container from impacting other containers or the host.

Why is that important? Because /proc/sys/fs/binfmt_misc is interacting with the kernel, and pushing a change to that would be considered a container escape since you're modifying the underlying host.

The next thing to cover is building an image vs running a container. When you build an image with the Dockerfile, you are defining the image filesystem and some metadata (labels, entrypoint, exposed ports, etc). Each RUN command executes that command inside a temporary container, based on the previous step's result, and when the command finishes it captures the changes to the container filesystem. When you mount another filesystem, that doesn't change the underlying container filesystem, so even if you could, the mount command would be a noop during the image build.

So if this is possible, you'll need to do it inside the container rather than during build time, that container will need to be privileged since doing things like mounting filesystems and modifying /proc requires access not normally given to containers, and you'll be modifying the host kernel in the process. You'd need to make the container entrypoint run the mount and register the binfmt_misc entry, and figure out what to do if the entry is already setup/registered, but possibly to a different directory in another container.

As an aside, when dealing with binfmt_misc and containers, the F flag is very important, though in your use case it's important that you don't have it. Typically you need the F flag so the binary is found on the host filesystem rather than searched for within the container filesystem namespace. The typical use case of binfmt_misc and containers is configuring the host to be able to run containers for different architectures, e.g. Docker Desktop can run amd64, arm64, and a bunch of other platforms today using this.

In the end, if you want to run a container as a one off to run a go command as a script, I'd skip the binfmt misc trick and make an entrypoint that does a go run instead. But if you're using the container for longer run processes where you want to periodically run a go file as a script, you'll need to do that in the container, and as a privileged container that has the ability to escape to the host.

No this is neither possible nor desirable.

If sep is empty, Split splits after each UTF-8 sequence.

— the docs.

So although bytes.Split does let you split at arbitrary points and break UTF-8 sequences apart, calling it with a separator of []byte("") won't do so.

If you profile the application, it will show most of the time is spent in

Based on the little bit of code you have shared, you would need to change your call site to await both the GoRun() method and the GetCompletedTask() method:

The problem is originating in lib/go_run/parser.rb rather than from the test itself. Whenever Ruby finds the GoRun::Parser definition, it goes looking for GoRun in the constant lookup table, but it won't be there, and so the program exits with an error.

Note that using lib/go_run.rb as an entry point also will not work, because go_run/parser.rb is required before GoRun is defined.

Part of the problem is using GoRun as both the project level namespace, and an entry point class.

There are a couple of idioms you should consider to fix this situation:

1. Make GoRun a top level module, used purely for namespacing. Move the logic that lives in the current logic into its own class, for example go_run/cli.rb. The go_run.rb file is then kept as a sort of manifest file, that requires the classes of your project.

2. Use the nested module- and class syntax. This will define the outer module if it isn't already.

3. Use a spec_helper.rb file that bootstraps your project using require 'go_run', to make sure everything is properly loaded before running your tests.