[master] Add etcd extra args support for K3s

[Oats87]

Proposed Changes

Add etcd extra args support for K3s

Types of Changes

CLI/Etcd changes

Verification

Run etcd with custom args, check to see that it actually runs with these custom args

Linked Issues

#4462

User-Facing Change

K3s now supports `--etcd-arg` to specify additional etcd arguments for running etcd

Further Comments

[briandowns]

This seems reasonable and very straightforward but I'm a little concerned with what values are passed in and how we handle them. ie should we do some introspection to prevent obvious foot-gun situations? Have we tested this for basic functionality? We should probably add some additional integration tests for this before merging given the ramifications of the change.

[galal-hussein]

LGTM, thanks!

[codecov-commenter]

Codecov Report

Merging #4463 (7a2cdc8) into master (41ff19d) will decrease coverage by 0.03%.
The diff coverage is 9.67%.

@@            Coverage Diff             @@
##           master    #4463      +/-   ##
==========================================
- Coverage   12.07%   12.04%   -0.04%     
==========================================
  Files         135      135              
  Lines        9148     9175      +27     
==========================================
  Hits         1105     1105              
- Misses       7808     7834      +26     
- Partials      235      236       +1     

Flag	Coverage Δ
inttests	0.76% <0.00%> (-0.01%)	⬇️
unittests	11.60% <9.67%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/apis/k3s.cattle.io/v1/zz_generated_deepcopy.go	0.00% <ø> (ø)
pkg/cli/cmds/server.go	0.00% <ø> (ø)
pkg/cli/server/server.go	0.00% <0.00%> (ø)
pkg/cluster/bootstrap.go	0.00% <0.00%> (ø)
pkg/daemons/config/types.go	50.00% <ø> (ø)
pkg/deploy/zz_generated_bindata.go	0.00% <ø> (ø)
pkg/static/zz_generated_bindata.go	0.00% <ø> (ø)
pkg/daemons/executor/executor.go	11.36% <3.70%> (-16.42%)	⬇️
pkg/daemons/executor/etcd.go	37.03% <100.00%> (ø)
pkg/etcd/etcd.go	16.62% <100.00%> (ø)
... and 1 more

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[Oats87]

How to Test:

This PR/enhancement adds --etcd-arg functionality to K3s.

One way to test this is to run K3s like:

k3s server --etcd-arg quota-backend-bytes=858993459 --etcd-arg "experimental-initial-corrupt-check=true"  --etcd-arg "log-rotation-config-json={\"maxsize\": 100, \"maxage\": 0, \"maxbackups\": 0, \"localtime\": false, \"compress\": false}" --etcd-arg "log-outputs=[default]"

then, inspect the logs it spits out looking for the fact that it's using 858993459 as the quota backend size, and checking the various other things that are set.

Any of the etcd parameters here: https://etcd.io/docs/v3.5/op-guide/configuration/ are settable via the arg, with the notable exception of the duration-type arguments as there is a known issue with setting those via config file.