Reformat the config file documentation format of DM, Lightning, TiCDC, TiFlash to the same as that of TiDB, TiKV, PD, TiProxy

[kennytm]

Change Request

Please answer the following questions before submitting your issue. Thanks!

1. Describe what you find is inappropriate or missing in the existing docs.

The config doc of DM, Lightning, CDC and TiFlash mostly just the config template verbatim. The explanation of each config is either laid out as a table, or worse, as inline TOML/YAML comments. The problems are

• Support engineers cannot easily link to a particular config item.
• Due to the format, the documentation of each config item is usually constrained to a single paragraph
• Inline comments are very difficult to read.

2. Describe your suggestion or addition.

These documentation should align with the format chosen by TiDB, TiKV and PD etc, using one <h3> section for each config item and one <h2> for each group.

The content of each config item can show the default value, possible ranges. Each item can have the "New in vX.Y" showing the supported version range. The description itself can be formatted and link to other documentations (unlike inline comments). Caveats can be explained in details without worrying about <td> size.

3. Provide some reference materials (such as documents and websites) if you could.

Config documentation which I consider bad:

• DM source https://docs.pingcap.com/tidb/stable/dm-source-configuration-file
• DM task https://docs.pingcap.com/tidb/stable/task-configuration-file-full
• dm-master https://docs.pingcap.com/tidb/stable/dm-master-configuration-file
• dm-worker https://docs.pingcap.com/tidb/stable/dm-worker-configuration-file
• Lightning https://docs.pingcap.com/tidb/stable/tidb-lightning-configuration
• cdc https://docs.pingcap.com/tidb/stable/ticdc-server-config
• TiCDC changefeed https://docs.pingcap.com/tidb/stable/ticdc-changefeed-config
• TiFlash https://docs.pingcap.com/tidb/stable/tiflash-configuration

Config documentation which are better:

• TiDB Binlog https://docs.pingcap.com/tidb/stable/tidb-binlog-configuration-file
• TiProxy https://docs.pingcap.com/tidb/stable/tiproxy-configuration
• tidb-server https://docs.pingcap.com/tidb/stable/tidb-configuration-file
• tikv-server https://docs.pingcap.com/tidb/stable/tikv-configuration-file
• pd-server https://docs.pingcap.com/tidb/stable/pd-configuration-file