Why are image digests as names not accepted?

[gzm0]

I'm trying to run an image with testcontainers that is built and loaded into the docker daemon by an external build system. At the point in time tc gets invoked, the image is already loaded into the docker daemon.

To avoid polluting the image namespace of the docker daemon, I'd like to refer to the image using the 64-byte hex string of the image (e.g. b94d01b4929562a35cdcfe80ca0d5fca222c3fdedf224af9a079dc23157e1363). Docker supports this (e.g. docker run b94d01b4929562a35cdcfe80ca0d5fca222c3fdedf224af9a079dc23157e1363).

However, it seems that tc (I've checked tc-java and tc-node), insists that images have a tag. So if I pass b94d01b4929562a35cdcfe80ca0d5fca222c3fdedf224af9a079dc23157e1363 as image name to DockerImageName.parse, it will expand it into b94d01b4929562a35cdcfe80ca0d5fca222c3fdedf224af9a079dc23157e1363:latest. Docker does not accept that:

$ docker run b94d01b4929562a35cdcfe80ca0d5fca222c3fdedf224af9a079dc23157e1363:latest
Unable to find image 'b94d01b4929562a35cdcfe80ca0d5fca222c3fdedf224af9a079dc23157e1363:latest' locally
docker: Error response from daemon: invalid repository name (b94d01b4929562a35cdcfe80ca0d5fca222c3fdedf224af9a079dc23157e1363), cannot specify 64-byte hexadecimal strings.
See 'docker run --help'.

tc fails with the same error message (HTTP 400 from docker daemon).

Relevant if/else branch for DockerImageName.parse:

testcontainers-java/core/src/main/java/org/testcontainers/utility/DockerImageName.java

Lines 95 to 98 in 3b8c869

	} else {
	repository = remoteName;
	versioning = Versioning.ANY;
	}

Versioning.ANY:

testcontainers-java/core/src/main/java/org/testcontainers/utility/Versioning.java

Lines 25 to 33 in 3b8c869

	@Override
	public String getSeparator() {
	return ":";
	}
	@Override
	public String toString() {
	return "latest";
	}

This lead me to dig how tc handles this when building images itself. It seems that both tc-node and tc-java generate a UUID to give the image a name:

testcontainers-java/core/src/main/java/org/testcontainers/images/builder/ImageFromDockerfile.java

Lines 67 to 69 in 3b8c869

	public ImageFromDockerfile() {
	this("localhost/testcontainers/" + Base58.randomString(16).toLowerCase());
	}

tc-node equivalent

This in turn makes me suspect that this was deliberate design decision which I'm trying to understand. Any insight into this would be highly appreciated.

If possible, I'd like to avoid generating arbitrary UUIDs for image identifiers since it will pollute the docker image namespace.

Is there a way to do this?

If this situation is accidental, would you be willing to accept a PR adding support for this? If yes, what is the process to ensure feature parity between the different language implementations? (I only care about Node, but I realize that keeping things in sync is very important).

[gzm0]

PR to change this on tc-node: testcontainers/testcontainers-node#663

[rocketraman]

I'm having this issue randomly with testcontainers-java also.