Why does an error occur when selecting sys.innodb_lock_waits in PMM?

MySQL & MariaDB
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1

I’m using pmm and when I try to look up sys.innodb_lock_waits in the panel edit to look up mysql’s lock holder and waiter information on the dashboard, I get an error saying db query error: query failed - please inspect Grafana server log for details. What could be the reason?

I am using AWS RDS and the version is mysql 8.0.32.

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2

Welcome to Percona Community @wanskim,

The error occur because PMM isn’t giving you an SQL prompt but graphQL. You cannot execute select * to the metric there. Also, it isn’t storing innodb_lock_waits “table” unless you explicitly export it in some specific format (I don’t know yet).
If you want what you’re querying, execute it against database and not PMM.

Thanks,
K

3

thank you for your reply

This error occurs when querying a table in the DB through a data source. Other tables do not generate errors, but the above error occurs only when querying sys.innodb_lock_waits.

Even tables other than that table (information_schema.innodb_trx) are searched well.

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4

oh! I see in the screenshot here that you’re using datasource as “mysql-1” a database. Well, the question is do you have sys schema on database? can you run this query directly on database?

5

Yes, tables from other schemas work fine.

6

As you mentioned, it’s AWS RDS mysql 8.0.32. It is most likely an issue for pmm rds exporter and AWS RDS mysql version.

Please report this as bug here https://perconadev.atlassian.net
You should provide the below details in the report, we will test and try to reproduce the same issue once you report this to https://perconadev.atlassian.net

  • AWS RDS MySQL and PMM version
  • How you are adding RDS instance to PMM monitoring.
  • Error details/ screenshot with error.