Master-Master Replication [Percona]

Question

Please forgive my ignorance but I do not have a ton of experience with MySQL. I am a web developer but overall I have pretty much just installed MySQL or spun up an RDS instance, connected to it and everything just works. However I am currently being tasked with creating a complete backup of our primary server (essentially high availability with a load balancer etc). So I thought now might be a good time to change how I haver our MySQL setup to take advantage of having 2 servers. Currently our MySQL lives on our primary servers and that will probably stay that way for now, however my goal with this new setup is to have 2 identical servers, both running the application and both having the exact same MySQL data structure / data. I want to be able to essentially open up the web application on one server, make a change, see it on the other or vica versa.

From my research it looks like what I want is called "Master-Master Replication" however it seems as if this is an older / more outdated approach? Every article I read is from ~2010-2012 and most people say it is depreciated and I should use Percona XtraDB Cluster, MySQL Group Replication, or Galera Cluster etc. I basically have no idea what any of that means and I am looking for the easiest way to get Master-Master type setup working. On top of that even if I wanted to use regular Master-Master replication it seems as if this is something specific to MySQL and not Percona which is what I actually use.

I know plenty about dev ops and can get everything but the MySQL up and running in no time but I would love some insight on the best way to do this. Currently servers are running Centos 7, Percona 5.7, Apache 2.4.

Answer 1

The easiest way to start is to setup a percona xtradb cluster with proxysql.

Percona xtradb cluster handles all the problems that are present in basic MySQL Source-Source Replication.
Both Galera and Percona Xtradb Cluster are same, as they use the same galera plugin, Only that Percona has customized it and added some extra features like in built proxysql (kind of load balancer for database).

Answer 2

Let's clear up one thing first. Percona is MySQL. If a feature is available on Oracle MySQL (the community version is what I am referring to here), then it is also available on Percona. Think of the two like a cake: MySQL is the base "cake" and Percona is the frosting/sprinkles/etc that go on top.

That being said you can absolutely do Master/Master using Percona MySQL. The standard/best practice is to configure this in active/hot-standby. Meaning, do not write to both nodes at the same time. Your application, or your middleware/proxy, must isolate writes to only one node. This will save you insane headaches when/if replication breaks.

ProxySQL is not a Percona product, but we do support it 100%. You can place ProxySQL in front of your M/M and setup the correct query rules to only route to one MySQL.

You are correct that the most modern solution here, and in my opinion, an easier solution, is to set up a 3-node Percona XtraDB Cluster (PXC). Again, Galera MySQL is the "cake" and PXC is all the extras on top. Group Replication is pie (just to continue the analogy.)

We consider a 3-node PXC fronted with ProxySQL to be one of the best HA solutions out there for MySQL. It is still best practice to only write to one node, and utilize the other 2 for read-only queries. If the primary node goes down, each of the other two have an up-to-the-transaction copy of the data. Again, ProxySQL helps route the traffic if primary goes down.

Backups can be taken from any PXC node using Percona XtraBackup in a non-blocking/hot fashion.