Galera Cluster Manager (interview test task)

This utility let's you create and monitor MySQL Galera cluster.

Compilation

Prerequisites

This project requires Go 1.10 or newer. If you haven't installed Go yet, use the binary installers available from the official Go website.

Compilation

• Install dep: https://github.com/golang/dep

go get -u github.com/golang/dep/cmd/dep

NB: if you cannot run dep after you installed it, try adding exporting the path:

export PATH=$PATH:$GOROOT/bin

• Set GOPATH to some directory:

export GOPATH=/home/joe/go-projects

• Clone the sources

mkdir -p /home/joe/go-projects/src
cd /home/joe/go-projects/src
git clone [email protected]:go-extras/galera-manager.git
cd  galera-manager

• Install dependencies:

dep ensure -vendor-only

• Run tests:

NB: for now skip this step as no tests exist at the moment.

go test ./...

• Build the binary:

go build -o bin/galera-manager

After running the last command you will get a ./bin/galera-manager executable.

Configuration

This tool does not have any configuration file.

How to use?

First of all, you must have Docker installed and running. For MacOS users you must use "storage-driver" : "aufs" in your config.

Install the cluster

NB: on linux you might need to prefix the commands with sudo.

bash-3.2$ ./bin/galera-manager install
[... docker image build and container creation commands will be shown ...]

Start the cluster

bash-3.2$ ./bin/galera-manager start
2018/05/26 12:11:44 Container [/node1] started
2018/05/26 12:11:45 Container [/node3] started
2018/05/26 12:11:45 Container [/node2] started

Check cluster status

bash-3.2$ ./bin/galera-manager start
2018/05/26 12:11:44 Container [/node1] started
2018/05/26 12:11:45 Container [/node3] started
2018/05/26 12:11:45 Container [/node2] started
bash-3.2$ ./bin/galera-manager status
2018/05/26 12:12:20 First node ([/node1]) container ID: 0397a525f1, status: Up 36 seconds
2018/05/26 12:12:20 Node [/node3] container ID: 1a4260823f, status: Up 35 seconds
2018/05/26 12:12:20 Node [/node2] container ID: 30f90e228c, status: Up 34 seconds
Node [/node1] has status Up 36 seconds
Node [/node3] has status Up 35 seconds
Node [/node2] has status Up 34 seconds
wsrep_provider_name Galera
wsrep_ready ON
wsrep_cluster_size 3

Start http server

./bin/galera-manager http-server

(no output will be shown)

The server will start bound to :8080 and can be accessed at http://localhost:8080.

The output via http server will now be pretty much the same as via the console command:

bash-3.2$ curl http://localhost:8080
Node [/node1] has status Up 2 minutes
Node [/node3] has status Up 2 minutes
Node [/node2] has status Up 2 minutes
wsrep_provider_name: Galera
wsrep_ready: ON
wsrep_cluster_size: 3

Stopping the nodes

bash-3.2$ ./galera-cluster stop
2018/05/26 12:16:31 Stopping container 1a4260823f...
2018/05/26 12:16:37 Success
2018/05/26 12:16:37 Stopping container 30f90e228c...
2018/05/26 12:16:47 Success
2018/05/26 12:16:47 Stopping container 0397a525f1...
2018/05/26 12:16:52 Success

Let's now check the status in our http endpoint:

bash-3.2$ curl http://localhost:8080
Node [/node1] has status Exited (0) 41 seconds ago
Node [/node3] has status Exited (0) 56 seconds ago
Node [/node2] has status Exited (137) 45 seconds ago
No node is running

Uninstalling the cluster

bash-3.2$ ./galera-cluster uninstall
2018/05/26 12:18:16 Removing container 1a4260823f...
2018/05/26 12:18:16 Success
2018/05/26 12:18:16 Removing container 30f90e228c...
2018/05/26 12:18:16 Success
2018/05/26 12:18:16 Removing container 0397a525f1...
2018/05/26 12:18:16 Success
2018/05/26 12:18:16 Removing network af6160f3ad...
2018/05/26 12:18:16 Success
2018/05/26 12:18:16 Removing image sha256:eeb...
2018/05/26 12:18:17 Success

Now, let's check again the http endpoint:

bash-3.2$ curl http://localhost:8080
no nodes found :unable to get containers

TODO

• Write tests
• Make http port configurable
• Make names (labels) configurable
• Better error handling
• Http output should be RESTful and there should be a JS UI for that
• Make it possible to expose MySQL ports
• Check cluster state via MySQL connection, not via command execution
• Check cluster state on all the nodes (optionally)
• Make purging child containers optional when uninstalling (for faster re-installs)
• Better logging facilities (use logrus library and error levels)