support rendering template when set "--local" option

[makocchi-git]

What problem does this PR solve?

tiup cluster template prints example yaml file.
I think that it is more useful if users can specify global values or servers in topology.yaml.
This PR enables generating sample topology.yaml with specify variables.

What is changed and how it works?

When set --local, it renders a template with some overridden variables such as global.user, global.group, etc by setting --user, --group and so on together.

This is sample output:

$ tiup cluster template --local --user ubuntu
...
global:
  # # The OS user who runs the tidb cluster.
  user: "ubuntu"
...

=======

$ tiup cluster template --local --user ubuntu --pd-servers 127.0.0.1,127.0.0.2
...
global:
  # # The OS user who runs the tidb cluster.
  user: "ubuntu"
...
pd_servers:
  - host: 127.0.0.1
  - host: 127.0.0.2
...

And also support tiup dm template --local.

$ tiup dm template --local --user ubuntu
...
global:
  # # The OS user who runs the tidb cluster.
  user: "ubuntu"
...

=======

$ tiup dm template --local --user ubuntu --master-servers m1,m2,m3
...
global:
  # # The OS user who runs the tidb cluster.
  user: "ubuntu"
...
master_servers:
  - host: m1
  - host: m2
  - host: m3
...

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Code changes

• Has exported function/method change
• Has exported variable/fields change
• Has interface methods change
• Has persistent data change

Side effects

• Possible performance regression
• Increased code complexity
• Breaking backward compatibility

Related changes

• Need to cherry-pick to the release branch
• Need to update the documentation

Release notes:

Support rendering example topology.yaml with specifying variables.

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• AstroProfundis

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[AstroProfundis]

Thanks for the PR! This is indeed a very useful feature. However, I feel the arguments are getting a little too complex. How about:

• Set default values for the skeleton struct
• Change our builtin examples to templates
• If no other arguments are set, use the default values to render the template
• If any custom argument is set, use the user input values to render the template (along with default ones)

So that the --skeleton argument is no longer needed, and all other argument are shortened as the --skeleton-xxx prefixes are also not needed.

[AstroProfundis]

And... Would you like to also add the same feature to tiup-dm? It would be better to adjust tiup-dm and tiup-cluster together, but it's also totally OK if you don't want to.

[codecov-commenter]

Codecov Report

Merging #1596 (b25d926) into master (956504c) will increase coverage by 35.01%.
The diff coverage is 41.79%.

@@             Coverage Diff             @@
##           master    #1596       +/-   ##
===========================================
+ Coverage   15.71%   50.72%   +35.01%     
===========================================
  Files         149      290      +141     
  Lines       15098    26486    +11388     
===========================================
+ Hits         2372    13434    +11062     
+ Misses      12208    11032     -1176     
- Partials      518     2020     +1502     

Flag	Coverage Δ
cluster	43.87% <53.57%> (?)
dm	26.06% <33.33%> (?)
integrate	50.72% <41.79%> (+35.01%)	⬆️
playground	13.47% <ø> (?)
tiup	15.71% <ø> (ø)
unittest	∅ <ø> (∅)

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

Impacted Files	Coverage Δ
components/dm/command/template.go	37.03% <33.33%> (ø)
components/cluster/command/template.go	40.35% <53.57%> (ø)
components/cluster/command/reload.go	80.64% <0.00%> (ø)
pkg/cluster/manager/transfer.go	51.13% <0.00%> (ø)
components/dm/command/destroy.go	63.15% <0.00%> (ø)
components/cluster/command/telemetry.go	24.00% <0.00%> (ø)
components/playground/instance/tikv.go	67.85% <0.00%> (ø)
components/dm/command/exec.go	87.50% <0.00%> (ø)
components/cluster/command/check.go	86.66% <0.00%> (ø)
components/cluster/command/prune.go	84.61% <0.00%> (ø)
... and 235 more

---

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[makocchi-git]

@AstroProfundis Thank you for your comments.

Set default values for the skeleton struct

Skelton default values are set by cobra functions. (same as --full or --local, etc)

Change our builtin examples to templates

I think that it is a bit hard to render a template completely. (especially full template)
Because there are too many structured options in pd_servers or tidb_servers, etc.
Of course I know skelton template can't render a complete one, so I think it is useful for customizing some parameters in demonstration environment, for example.
This is the reason why I created a skelton way as a new rendering option.

So I suggest and agree replacing --local to skelton rendering.
(I agree too that --skelton-xxx is a lttile bit annoying....😅)
I'd like to hear your opinions.

tiup-dm

OK, I'll try.

[AstroProfundis]

So I suggest and agree replacing --local to skelton rendering.
(I agree too that --skelton-xxx is a lttile bit annoying....sweat_smile)
I'd like to hear your opinions.

Sounds good. I'm just feeling that --skeleton and --skeleton-xxx are redundant and may be confusing the user, I think it's ok to let those --user xxx arguments only work for --local template as of now, we can add more rendering ability to other templates in the future and that don't seems to me that would broke anything.

[makocchi-git]

Now supports tiup-dm template --local and add some unit tests.

[makocchi-git]

rebased

[AstroProfundis]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: 0cbbf61

[makocchi-git]

Sorry. I fixed ioutil package.

[AstroProfundis]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: b25d926