Bug Report: Changing default of replica_net_timeout can cause issues while upgrading

[GuptaManan100]

Overview of the Issue

Changing the default value of replica_net_timeout(https://dev.mysql.com/doc/refman/8.0/en/replication-options-replica.html#sysvar_replica_net_timeout) can cause issues since the heartbeat_interval value might not change. That value is only initialised when a new mysql instance starts. After that if a MySQL restarts with the updated my.cnf with the new replica_net_timeout value, then the replication between primary and replica will be broken.

Reproduction Steps

Start a v19 cluster and upgrade to v20. Restart the mysql of a replica with the new my.cnf and see that replication is broken.

Binary Version

main

Operating System and Environment details

-

Log Fragments

No response

[GuptaManan100]

With the feature request #15880 implemented in VTOrc that can fix this configuration problem, we just need to revert the changes in #15663 and #15689 and make the default change in the next release once the VTOrc fixes are guaranteed to be present.