Add additional metric to Mysql receiver

[samiura]

Component(s)

receiver/mysql

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

When monitoring a MySQL database, few useful metrics are the number of qcache hits, qcache not cached, number of queries in qcache in each database. Prior to Mysql 5.7.20 qcache metrics are used hence the need for these metrics

Describe the solution you'd like

The mysql receiver already queries global status variables information. I would add the three additional metrics to the list

Describe alternatives you've considered

No response

Additional context

No response

[github-actions]

Pinging code owners:

• receiver/mysql: @djaglowski

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[djaglowski]

Prior to Mysql 5.7.20 qcache metrics are used hence the need for these metrics

Am I understanding correctly that these metrics are not available after 5.7.20?

[samiura]

@djaglowski yes correct.

[djaglowski]

@samiura, 5.7 was recently deprecated and we claim support for 8.0+, so I think we shouldn't add these metrics.

The sqlquery receiver should be able to handle these though, so I'd recommend using that instead. It might be worth adding an example configuration here.

[samiura]

@djaglowski I understand that and I will close the PR.

[atoulme]

Closing this issue as not planned as the enhancement was rejected as MySQL 5.7 is not supported.