[docs] AZ tutorial: High availability MySQL

[geoffreynyaga]

This PR adds a new tutorial for setting up and working with AZ. It provides step-by-step guidance to help users get started quickly with AZs and work on a primary-replica setup across two VMs.

Additions

• Added an introductory tutorial covering AZ setup
• Documented prerequisites and installation steps
• Primary and replica setup for MySQL

Notes

• There is also an additional explanation page for Availability Zones

[codecov]

Codecov Report

❌ Patch coverage is 90.16393% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.67%. Comparing base (a0008b1) to head (d5e2b0d).
⚠️ Report is 190 commits behind head on availability-zones.

Files with missing lines	Patch %	Lines
src/daemon/daemon.cpp	25.00%	12 Missing ⚠️

Additional details and impacted files

@@                  Coverage Diff                   @@
##           availability-zones    #4360      +/-   ##
======================================================
+ Coverage               89.35%   89.67%   +0.31%     
======================================================
  Files                     259      268       +9     
  Lines                   15744    16270     +526     
======================================================
+ Hits                    14068    14590     +522     
- Misses                   1676     1680       +4     

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[sharder996]

Hey @geoffreynyaga, after extensive testing I think I'm finally able to give some feedback on this.

First of, after having trouble getting the MySQL setup to work following this guide I used the Google doc version which I had better success with. I actually think the Google doc version is better written than this one here and fixes a lot of the things I was going to leave comments on in this review. I did still have some additional comments which I left there.

As far as testing goes, I got the setup working properly on macOS after tinkering a bit. So, pending my comments on the Google doc, I think that side is good.

For Ubuntu, I was not able to get the setup working with issues arising when trying to get mysql-primary to rejoin the cluster. Below are some logs parsed out of /var/log/mysql/error.log:

2025-10-29T04:58:56.540884Z 11 [ERROR] [MY-010584] [Repl] Replica I/O for channel '': Error connecting to source '[email protected]:3306'. This was attempt 10/86400, with a delay of 60 seconds between attempts. Message: Access denied for user 'replica'@'10.32.29.1' (using password: YES), Error_code: MY-001045
2025-10-29T04:59:01.244290Z 27 [Warning] [MY-010056] [Server] Host name 'scott-Darter-Pro' could not be resolved: Temporary failure in name resolution

I find it interesting that the database is trying to connect to 10.32.29.1, which is the IP address of my host and not the IP of the new primary.

Another thing I find interesting is that on macOS, the two VMs which should be in different availability zones are located within the same subnet, i.e. 192.168.2.* where as on Ubuntu they are in different subnets, i.e. 10.152.207.* and 10.32.29.*. I'm not sure, but wouldn't be surprised if this is related to the issues I have on Ubuntu as described above.

@Sploder12 maybe you are able to provide some more insight into what is going on here.

[sharder996]

Might want to mention here for the user to enter their created password from before, i.e., SecureRootPass123

[sharder996]

Suggested change

	grep -i 'CHANGE MASTER' full.sql
	grep -i 'CHANGE MASTER TO MASTER_LOG_FILE' full.sql

Otherwise, I get so much text I have to scroll through it.

[sharder996]

Maybe mention what should be returned?

[sharder996]

Maybe mention that this isn't simply adding settings, some of them exist already and must be overwritten.

[sharder996]

Add a code block as before with sudo nano /etc/mysql/mysql.conf.d/mysqld.cnf

[sharder996]

idem Be more clear where

[sharder996]

Should we add an additional command to remove the certificates from the host? Just to be tidy and to not encourage users to leave their certificates lying around.

[sharder996]

idem Be more clear where

[sharder996]

idem Clean up after ourselves

[sharder996]

replication user credentials

Its unclear what this is supposed to be.