Clarify the error message returned when trying to use the docker runtime
on a Kubelet that was compiled without Docker.
We removed the "w/" and "w/o", which can be confusing abbreviations, and
also add slightly more detail on the actual error.
We do not want to run the `cadvisor/docker` init when we are using the
dockerless build tags. We can ensure this by isolating into a separate
file with the proper build tag constraints.
As the final step, add the `dockerless` tags to all files in the
dockershim. Using `-tags=dockerless` in `go build`, we can compile
kubelet without the dockershim.
Once cadvisor no longer depends on `docker/docker`, compiling with
`-tags=dockerless` should be sufficient to compile the Kubelet w/o a
dependency on `docker/docker`.
DockerLegacyService interface is used throughout `pkg/kubelet`.
It used to live in the `pkg/kubelet/dockershim` package. While we
would eventually like to remove it entirely, we need to give users some form
of warning.
By including the interface in
`pkg/kubelet/legacy/logs.go`, we ensure the interface is
available to `pkg/kubelet`, even when we are building with the `dockerless`
tag (i.e. not compiling the dockershim).
While the interface always exists, there will be no implementations of the
interface when building with the `dockerless` tag. The lack of
implementations should not be an issue, as we only expect `pkg/kubelet` code
to need an implementation of the `DockerLegacyService` when we are using
docker. If we are using docker, but building with the `dockerless` tag, than
this will be just one of many things that breaks.
`pkg/kubelet/legacy` might not be the best name for the package... I'm
very open to finding a different package name or even an already
existing package.
We can remove all uses of `dockershim` from `cmd/kubelet`, by just
passing the docker options to the kubelet in their pure form, instead of
using them to create a `dockerClientConfig` (which is defined in
dockershim). We can then construct the `dockerClientConfig` only when we
actually need it.
Extract a `runDockershim` function into a file outside of `kubelet.go`.
We can use build tags to compile two separate functions... one which
actually runs dockershim and one that is a no-op.
Remove one of two uses of Dockershim in `cmd/kubelet`. The other is for
creating a docker client which we pass to the Kubelet... we will handle
that refactor in a separate diff.
I'm fairly confident, though need to double check, that no one is
actually using this experimental dockershim behavior. If they are, I
think we will want to find a new way to support it (that doesn't require
using the Kubelet only to launch Dockershim).
Following changes in #87730, Kubelet is directly hcsshim to gather stats.
However, unlike `docker stats` API that was used before, hcsshim does not
keep information about exited containers.
When the Kubelet lists containers (`docker_container.go:ListContainers()`),
it sets `All: true`, retrieving non-running containers.
When docker stats is called with such container id, it'll return a valid JSON
with all values set to 0. The non-running containers are filtered later on in the process.
When the hcsshim is called with such container id, it'll return an error, effectively
stopping the stats retrieval for all containers.
