Add an option for tasks to mutate the State object

[xmudrii]

What this PR does / why we need it:

We have a task to determine the pause image by asking kubeadm what pause image we should use:

kubeone/pkg/tasks/kubeadm_config.go

Lines 30 to 54 in 5a489d6

	func determinePauseImage(s *state.State) error {
	if rc := s.Cluster.RegistryConfiguration; rc == nil || rc.OverwriteRegistry == "" {
	return nil
	}
	s.Logger.Infoln("Determining Kubernetes pause image...")
	return s.RunTaskOnLeader(determinePauseImageExecutor)
	}
	func determinePauseImageExecutor(s *state.State, node *kubeoneapi.HostConfig, conn executor.Interface) error {
	cmd, err := scripts.KubeadmPauseImageVersion(s.Cluster.Versions.Kubernetes)
	if err != nil {
	return err
	}
	out, _, err := s.Runner.RunRaw(cmd)
	if err != nil {
	return fail.SSH(err, "getting kubeadm PauseImage version")
	}
	s.PauseImage = s.Cluster.RegistryConfiguration.ImageRegistry("registry.k8s.io") + "/pause:" + out
	return nil
	}

The output from kubeadm is taken and the State object is updated by using state.PauseImage = .... However, that doesn't work because when running a task, we're creating a shallow copy of the State object and we use that one for running the task:

kubeone/pkg/state/task.go

Line 67 in 5a489d6

ctx := s.Clone()

Copying the State object is required because we might be running a task concurrently and multiple goroutines editing the same struct concurrently is never a good idea. But we still need a way to mutate the State from a task, for example, in this case, the only way to get the pause image is to ask kubeadm.

This issue is addressed by adding a state mutator function to the task executor (RunTaskOnNodes). This mutator function is guarded with a mutex so that it's safe to run it concurrently. This PR also integrates this mutator into a task responsible for getting the pause image, so this is now supposed to work properly.

What type of PR is this?

/kind bug

Does this PR introduce a user-facing change? Then add your Release Note here:

Use the pause image from `registry.k8s.io` for all Kubernetes releases

Documentation:

NONE

[xmudrii]

/cherrypick release/v1.5

[kubermatic-bot]

@xmudrii: once the present PR merges, I will cherry-pick it on top of release/v1.5 in a new PR and assign it to you.

In response to this:

/cherrypick release/v1.5

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[xmudrii]

/cherrypick release/v1.4

[kubermatic-bot]

@xmudrii: once the present PR merges, I will cherry-pick it on top of release/v1.4 in a new PR and assign it to you.

In response to this:

/cherrypick release/v1.4

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[kubermatic-bot]

LGTM label has been added.

Git tree hash: 1a19b608c6e286857a15e6661488b6f400eb85cb

[ahmedwaleedmalik]

/approve

[kubermatic-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahmedwaleedmalik

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [ahmedwaleedmalik]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[kubermatic-bot]

@xmudrii: new pull request created: #2529

In response to this:

/cherrypick release/v1.5

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[kubermatic-bot]

@xmudrii: #2528 failed to apply on top of branch "release/v1.4":

Applying: Add an option for tasks to mutate the State object
Using index info to reconstruct a base tree...
M	pkg/state/task.go
M	pkg/tasks/kubeadm_config.go
M	pkg/tasks/tasks.go
Falling back to patching base and 3-way merge...
Auto-merging pkg/tasks/tasks.go
CONFLICT (content): Merge conflict in pkg/tasks/tasks.go
Auto-merging pkg/tasks/kubeadm_config.go
CONFLICT (content): Merge conflict in pkg/tasks/kubeadm_config.go
Auto-merging pkg/state/task.go
CONFLICT (content): Merge conflict in pkg/state/task.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 Add an option for tasks to mutate the State object
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherrypick release/v1.4

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.