understanding-tidb: Introduction of TiDB architecture

[tisonkun]

Signed-off-by: tison wander4096@gmail.com

What issue does this PR solve?

• close Write down the first version of Introduction of TiDB architecture #23

What is changed:

Write down the first version of Introduction of TiDB architecture, making use of https://pingcap.com/blog-cn/tidb-source-code-reading-2/

[dragonly]

I suggest changing "you" to "we", which reads much warm and comfortable for me :D

[tisonkun]

I suggest changing "you" to "we", which reads much warm and comfortable for me :D

Thanks for your review. Could you add suggestions or send a pull request to this branch?

[tisonkun]

I suggest changing "you" to "we", which reads much warm and comfortable for me :D

With a walkthrough I think keep using "you" to talk with the reader is smoothly. They are not "we" because they have their own opinion.

[tisonkun]

cc @djshow832 @zimulala PTAL

[djshow832]

There is a big change to the packages, especially for the cmd and util directories. util has nearly 50 packages, which is almost impossible to maintain. Maybe we don't need to list all the packages, or just give an outline of cmd and util?

[tisonkun]

Make sense. I will remove some of sub packages in this run. But maybe we'd better structure our codebase to be clear to express.

[djshow832]

It's a little out of date. E.g. the storage engine can be TiFlash, and there are more background workers now. But I think it's basically fine.

[tisonkun]

@djshow832 ok. Would you mind to draw a picture (maybe by hands) or describe the architecture in the corresponding issue #23 or creating a new issue so that we can update it later?

[djshow832]

Creating an issue sounds fine to me. I'll do it.

[tisonkun]

Updated the content, please take a look @djshow832 @zz-jason .

Although I think the package structure of "util" should be refactor to be clear to express but let's describe the current stat for now.

[zz-jason]

LGTM