Updating service parameters unlinks historical QAN data

[skurpad7]

Description

In a MySQL service configured on PMM, we are unable to run Explain on a few queries on the QAN dashboard as they are truncated because they're greater than 2KB in length. The resolution for this issue is to increase the --max-query-length parameter for the service. Currently, PMM does not support updating the service configuration. I came across this community post which suggests removing the MySQL service and then adding it again with the --max-query-length=-1 parameter as it is not expected to delete historical data.

I tested the same and noticed that although the older queries are not erased, PMM throws an error when I try to run Explain on the QAN dashboard.

As seen below, before removing the service, Explain on the query works:

Once the service is removed and added back with the below command, Explains stop working with the following error: Service with ID "c5179c1a-04e9-49a7-a878-53c455248906" not found..

root@localhost:~# pmm-admin remove mysql
Service removed.

root@localhost:~# pmm-admin add mysql --username=<username> --password=<password> --query-source slowlog --size-slow-logs="-1GiB" --socket /run/mysqld/mysqld.sock  --service-name=mysql1 --max-query-length=-1
MySQL Service added.
Service ID  : f08aca1c-40fc-47d3-bffd-388cf6b4d6d0
Service name: mysql1

Table statistics collection enabled (the limit is 1000, the actual table count is 342).

Expected Results

• Explains on the older queries still work.

Actual Results

• Explains on the older queries stop working with error Service with ID "<previous_id>" not found..

Version

PMM Server and Client v3.5.0

Steps to reproduce

• Setup a MySQL service on PMM.
• Run a query through MySQL such that it is recorded on QAN.
• Verify that Explain on the query works.
• Remove the service and add it again with the same name.
• It is seen that Explain no longer works on the old query.

Code of Conduct

• I agree to follow Percona Community Code of Conduct