This example will:
- Build a consul master, a demo application, and as many PXC nodes as you'd like
- Utilize service discovery "sidecars" to integrate the PXC nodes into Consul (this keeping a clean separation of a "pure" PXC container)
- Utilize the service discovery DNS system too:
- Pull nodes into the cluster (after the 1st starts)
- Randomly query mysql servers from the application
An opinonated distributed application for service discover, health checks, and K/V store. We're going to use it to coordinate discovery or peer Percona nodes as well as locating random targets within the percona cluster for the application.
https://www.percona.com/software/mysql-database/percona-xtradb-cluster
A derivative MySQL with many performance enhancements that integrates Galera for multi-master, synchronous replication. Meaning: read/write to any node with ACID guarantees.
Get everything built with 01-build-all.sh. Feel free to inspect the Dockerfiles, everything is relatively straight forward, but some quirks are noted in the Dockerfiles and start.shs as needed.
Next, run 02-start-consul.sh to get our service discover, health check system up and running. This will also provide a web ui which can be accessed by browsing to the IP for you host at port 8501, for example http:https://192.168.1.50:8501/.
Now, let's get the app up with 03-start-app.sh. The app is a really, really simple reactphp app because it requires very little to implement (and because I know PHP best and could bang it out). Once started, you can visit that application at port 32875.
At this point, the app will be quite empty. No servers, no DNS records, can't connect to mysql. Well, yeah, we haven't started any nodes yet!
So, run 04-start-pxcnode.sh 1. Note the 1 there, it's important -- you're starting the first node. You can check out consul or the application and F5 bomb your keyboard to watch for it to come up. It's usually pretty quick though, so you might miss it.
What's important to note here is that this command actually starts 2 containers. The first is a (mostly) generic PXC container. This container will run a PXC instance, or attempt to join one if it can be found at a specific domain name (pxc.service.consul). A second container is started which will monitor the first and register it as a service with the consul cluster. This is a nice way of desinging so that the PXC container doesn't even need to know about the service discovery system, making it less coupled.
Now for the real fun! 04-start-pxcnode.sh 2 -- that'll start a second node, which will discover the first node (thanks consul!) and join the cluster. Then, as it automatically grabs all the latest data, once it's done the health check will go green (consul again) and the app will start seeing it as a viable, randomly discovered host for mysql connections.
You can continue adding nodes as you wish and watch as they all come up and spread the read/write load further.