[WIP] Add "platform" column to docker ps

[thaJeztah]

CLI changes for moby/moby#42464

With this change:

docker create armhf/hello-world
docker create hello-world
docker ps -a
CONTAINER ID IMAGE PLATFORM COMMAND CREATED STATUS PORTS NAMES
a020fcae5f4d hello-world linux/amd64 "/hello" 5 seconds ago Exited (0) 3 seconds ago vigorous_yalow
499a18874987 armhf/hello-world linux/arm64 "/hello" 58 seconds ago Exited (0) 57 seconds ago hardcore_brown
docker ps -a --format=raw
container_id: a020fcae5f4d
image: hello-world
platform: linux/amd64
command: "/hello"
created_at: 2021-07-05 07:08:19 +0000 UTC
state: exited
status: Exited (0) About an hour ago
names: vigorous_yalow
labels:
ports:
container_id: 499a18874987
image: armhf/hello-world
platform: linux/arm64
command: "/hello"
created_at: 2021-07-05 07:07:26 +0000 UTC
state: exited
status: Exited (0) About an hour ago

names: hardcore_brown
labels:
ports:

docker ps -a --format '{{json .}}' | jq .
{
"Command": "\"/hello\"",
"CreatedAt": "2021-07-05 07:08:19 +0000 UTC",
"ID": "a020fcae5f4d",
"Image": "hello-world",
"Labels": "",
"LocalVolumes": "0",
"Mounts": "",
"Names": "vigorous_yalow",
"Networks": "bridge",
"Platform": "linux/amd64",
"Ports": "",
"RunningFor": "52 seconds ago",
"Size": "0B (virtual 13.3kB)",
"State": "exited",
"Status": "Exited (0) 51 seconds ago"
}
{
"Command": "\"/hello\"",
"CreatedAt": "2021-07-05 07:07:26 +0000 UTC",
"ID": "499a18874987",
"Image": "armhf/hello-world",
"Labels": "",
"LocalVolumes": "0",
"Mounts": "",
"Names": "hardcore_brown",
"Networks": "bridge",
"Platform": "linux/arm64",
"Ports": "",
"RunningFor": "About a minute ago",
"Size": "0B (virtual 1.64kB)",
"State": "exited",
"Status": "Exited (0) About a minute ago"
}

To be discussed: what should the presentation be of platform if an "os variant" is present?

For example (from docker manifest inspect hello-world);

{
"mediaType": "application/vnd.docker.distribution.manifest.v2+json",
"size": 1125,
"digest": "sha256:90e120baffe5afa60dd5a24abcd051db49bd6aee391174da5e825ee6ee5a12a0",
"platform": {
"architecture": "amd64",
"os": "windows",
"os.version": "10.0.17763.1999"
}
}

- Description for the changelog

- A picture of a cute animal (not mandatory but encouraged)

[thaJeztah]

Some tests are failing because I didn't update them yet for the new output.

We need to discuss whether or not the PLATFORM column should be shown by default, or if it should be "optional" (as output is already quite wide).

Mixed platforms may currently be something that occurs often (thinking of Docker Desktop on Apple m1), but may become less common (once arm64 containers become more "standard?"). From that perspective (architecture being useful information during the "transition"), perhaps it should remain "optional".

[tianon]

IMO most users will not be running multiplatform on one system (esp. outside the M1 userbase), so we shouldn't include it by default (the default output is already v. v. wide, as you've noted).

[thaJeztah]

IMO most users will not be running multiplatform on one system (esp. outside the M1 userbase), so we shouldn't include it by default (the default output is already v. v. wide, as you've noted).

Yes, I agree. I started with this and thought "this is useful information", but when I started to update the docs, I started to doubt if that was a good idea.

Let me change this to;

• Not show by default (in the default table view)
• Add an example that shows how to use the new information in a custom --format (or custom format in ~/.docker/config.json)
• I'll keep it by default in the --format=raw output (although I doubt many users use that formatting)

Perhaps one remaining question: what do we want docker ps -a --format '{{json .}}' to show?

1. Platform: "os/arch/variant" (string presentation of Platform)
2. Platform: {"OS": "os", "Architecture": "arch" ....}
3. combination of the above? (e.g. OSArch field with combined, and Platform with struct?)

• 1. makes it more easy to use (--format '{{ . }}), but will "hide" the nitty-gritty details
• 2. shows all details (closer to API response), but cumbersome to use if you "just want os/arch"
• 3. will create a lot of noise. Also wondering if it's possible (haven't tried) to make {{ json .Platform}} return the "struct" and {{ .Platform}} return the string presentation. (if anyone knows the answer to that or has an example, let me know!)

[tianon]

• 3. will create a lot of noise. Also wondering if it's possible (haven't tried) to make {{ json .Platform}} return the "struct" and {{ .Platform}} return the string presentation. (if anyone knows the answer to that or has an example, let me know!)

Isn't that "just" a struct that also has a String() method? (This would definitely be my preference.)

https://play.golang.org/p/i4FOcAfAg7q

[thaJeztah]

• superseded by docker ps: add "Platform" as formatting option #6042