I´m not sure, what happened to my post from last week. But it's strange that 5 days have passed, and my post doesn't appear anywhere.
Because I'm afraid that my post will never appear, here is my question again:
I want to set up a complete server (apache, mysql 5.7) as a fallback of a productive server. The synchronization on file level using rsync and cronjob is already done.
The mysql-replication is currently the problem. More precisely: the choice of the right replica method.
Multi primary group replication seemed to be the most suitable method so far. In case of a longer production downtime, it is possible to switch to the fallback server quickly via DNS change. Write accesses to the database are possible immediately without adjustments.
So far so good: But, if the fallback-server fails, it is in unreachable status and the production-server switches to read only, since its group no longer has the quota. This is of course a no-go. I thought it might be possible using different replica variables: If the fallback-server is in unreachable state for a certain time (~5 minutes), the production-server should stop the group_replication and start a new group_replication. This has to happen automatically to keep the read-only time relatively low. When the fallback-server is back online, it should be manually added to the newly started group. But if I read the various forum posts and documentation correctly, it's not possible that way. And running a Group_Replication with only two nodes is the wrong decision anyway.
Is the master - slave replication the only one that can be considered for such a fallback system? https://dev.mysql.com/doc/refman/5.7/en/replication-solutions-switch.html
Or does the Group_Replication offer possibilities after all, if you can react suitably to the quota problem? Possibilities that I have overlooked so far.
Many thanks and best regards