support global status like 'uptime'

[morgo]

Feature Request

Is your feature request related to a problem? Please describe:

TiDB does not support the status variable 'uptime'. MySQL dbas use it idiomatically:

• I restart the server, I check it is the correctly rebooted.
• My client disconnected. Was it because of a server crash? check uptime.
• has the server freshly started? = slow performance (not applicable to tidb, since it's stateless).

So it is not critical but helps improve 'comfort'.

Describe the feature you'd like:

SHOW GLOBAL STATUS like 'Uptime' should report uptime in seconds.

Describe alternatives you've considered:

N/A

Teachability, Documentation, Adoption, Migration Strategy:

Compatibility with MySQL.

[laidahe]

I found the command is show status like 'uptime' not show global VARIABLES ....

[morgo]

I found the command is show status like 'uptime' not show global VARIABLES ....

Yes, you are right! I've updated the description.

[laidahe]

How can the command be implemented? Is there any similar pr? I want to implement it.

[morgo]

@laidahe , yes see: #8888

[laidahe]

You have implemented it?But I can not see test cases in #8888. @morgo

[morgo]

I am looking for feedback on how to test (see checklist). The obvious way is to use sleep, but I am not sure that is acceptable :-) Looking for feedback.