Stop signal

[runcom]

Who is going to define the stop signal for a container? Is this an image thing or a runtime thing?

[wking]

On Sun, Jan 29, 2017 at 04:23:06AM -0800, Antonio Murdaca wrote: Who is going to define the stop signal for a container? Is this an image thing or a runtime thing?

I think it's a runtime thing, since it's sent from the runtime to the container process. Why would it be an image thing? And I've tried to clear up some of the currently-ambiguous spec wording [1] in opencontainers/runtime-spec#513 by requiring POSIX signals for platforms that support them [2]. [1]: https://github.com/opencontainers/runtime-spec/blob/v1.0.0-rc3/runtime.md#kill [2]: https://github.com/opencontainers/runtime-spec/pull/513/files#diff-0c1e5a5baa5649945697a530e09acbf5R194

[runcom]

In the Docker scherma for the config, it's an image thing. Hence this question.

[runcom]

And right now, it's both missing in image and runtime under OCI? Or am I blind?

[wking]

On Sun, Jan 29, 2017 at 03:18:49PM -0800, Antonio Murdaca wrote: And right now, it's both missing in image and runtime under OCI? Or am I blind?

It's not in the image spec: image-spec$ git grep -i signal v1.0.0-rc3 …no hits… The runtime spec currently has very vague “MUST send the specified signal” [1]. The opencontainers/runtime-spec#513 language I linked earlier is: * *`--signal <SIGNAL>`* The signal to send (defaults to `TERM`). The runtime MUST support `TERM` and `KILL` signals with [the POSIX semantics][posix-signals]. The runtime MAY support additional signal names. On platforms that support [POSIX signals][posix-signals], the runtime MUST implement this command using POSIX signals. On platforms that do not support POSIX signals, the runtime MAY implement this command with alternative technology as long as `TERM` and `KILL` retain their POSIX semantics. Runtime authors on non-POSIX platforms SHOULD submit documentation for their TERM implementation to this specificiation, so runtime callers can configure the container process to gracefully handle the signals. Which seems sufficient to me. If the image authors have an opinion on which signal their container process is looking for, I recommend covering that in a config annotation: "org.opencontainers.signal.stop": "RTMIN+3" that would get copied over to the runtime config (once #492 lands) and the runtime caller could look that up and pick the appropriate phrasing for ‘kill’ (although as opencontainers/runtime-spec#513 stands, there's no requirement to support RTMIN+3). [1]: https://github.com/opencontainers/runtime-spec/blob/v1.0.0-rc3/runtime.md#kill

[stevvooe]

This should have been picked up from docker config: https://github.com/docker/docker/blob/master/api/types/container/config.go#L59.

Feel free to PR the addition.

[runcom]

But that is "container config" in docker, is that still OK to move that field in config? I'm making a pr as we speak though.

[runcom]

Nevermind I see it's in the image config.

[stevvooe]

@runcom I didn't see it in the OCI specification. Is it there?

[runcom]

Nope, I'll add it, sorry for the confusion.