fruitful playground - tikv-slim mode

[tisonkun]

Feature Request

Feature Description

So far, tiup playground by default create a tidb-fullstack cluster with 1 tidb + 1 tikv + 1 pd + 1 tiflash deployment. It is good for tidb audience, but not great for tikv-only audience, who just wants tikv + pd.

I'd like to introduce a tikv quickstart guide and recommend tiup as the defaulut, but it is an understanding burden for new user with current tiup he must set --db 0 --tiflash 0 and likely asks "what db / tiflash is".

Thus I propose we introduce a tikv-slim mode for playground which builds on the top of instance settings and provides fruitful feature for tikv-only audience, with which the experience becomes

$ tiup playground --mode tikv-slim

... and it starts 1 tikv + 1 pd only.

Rough Technical Design

The interface above leads to a minimal change set of code. Generally specking tiup currently hardcode the default option as below.

tiup/components/playground/main.go

Lines 79 to 97 in fa0a7ce

	opt := &bootOptions{
	tidb: instance.Config{
	Num: 1,
	UpTimeout: 60,
	},
	tikv: instance.Config{
	Num: 1,
	},
	pd: instance.Config{
	Num: 1,
	},
	tiflash: instance.Config{
	Num: 1,
	UpTimeout: 120,
	},
	host: "127.0.0.1",
	monitor: true,
	version: "",
	}

We can introduce a new config named mode(consider it!) which has options "tidb-fullstack"(default), and "tikv-slim".

tidb-fullatsack is the default and acts as current, while tikv-slim will populate the default config with "tikv.Num = 1" and "pd.Num = 1" only, without setting up tidb & tiflash. Other configs will be respected later one by one.

[tisonkun]

closed by #1333

[tisonkun]

@iosmanthus what if we move kv-only to mode design above?

[tisonkun]

@AstroProfundis I'm trying to use a painter algorithm for populate options layer by layer, but fail because the default value cannot be empty and trivially be ignored.

For example, I'd like make TiDB.Num to be blank(None in Rust as Option), and using --mode to define its default value while it can be later overwritten by --db. But it is tricky because cobra doesn't provide None but always a default value. And thus --db always have a default value that I don't know it is from user or just default.

[tisonkun]

You can take this patch as an input.

patch.diff.txt

https://github.com/pingcap/tiup/compare/master...tisonkun:mode?expand=1