Add support of the command READONLY & READWRITE

[singular-seal]

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• I had searched in the issues and found no similar issues.

Motivation

1. redis cluster utilize readonly to support reading from slave node
2. go-redis will send a 'readonly' command to server when 'ReadOnly' option is true during initialisation which would incur an error response from kvrocks 'ERR unknown command readonly' because kvrocks doesn't support command 'readonly'
3. this is important because without reading from slave a shard is not readable during failover which is not acceptable for some businesses

Solution

No response

Are you willing to submit a PR?

• I'm willing to submit a PR!

[git-hulk]

@singular-seal Thanks for your feedback.

[LiuYuHui]

Hi @git-hulk, I want to help implement this feature, could you give me some suggestions on where to start? thanks a lot!

[git-hulk]

@LiuYuHui Thank you! Go ahead.

[jihuayu]

Hi @LiuYuHui.
You can add a flag in redis::Connection to store if this connection enables read queries.
You can add new commands in cmd_server.cc

The following code may be the code you need to modify.

• https://github.com/apache/kvrocks/blob/unstable/src/cluster/cluster.cc#L804-L807

If you have any other questions, feel free to ask me.