MOCO is a MySQL operator on Kubernetes. Its primary function is to manage MySQL clusters using GTID-based semi-synchronous replication. It does not manage group replication clusters.

MOCO is designed to have the following properties.

• Compatibility with the standard MySQL
  • This is the reason that MOCO does not adopt group replication that has a number of limitations.
• Safety
  • MOCO only allows writes to a single instance called the primary at a time.
  • MOCO configures loss-less semi-synchronous replication with sufficient replicas.
  • MOCO detects and excludes instances having errant transactions.
• Availability
  • MOCO can quickly switch the primary in case of the primary failure or restart.
  • MOCO allows up to 5 instances in a cluster.

Blog article: Introducing MOCO, a modern MySQL operator on Kubernetes

• MySQL: 8.0.18, 8.0.25, 8.0.26, 8.0.27, 8.0.28, 8.0.30, 8.0.31, 8.0.32, 8.0.33, 8.0.34, 8.0.35
• Kubernetes: 1.25, 1.26, 1.27

MOCO supports (tests) the LTS releases of MySQL 8. Innovation releases would probably work. But they are not tested in our CI.

• Cluster with odd number of MySQL instances
• kubectl plugin
• Replication from an external MySQL instance
• Manual and automatic switchover of the primary instance
• Automatic failover of the primary instance
• Backup and Point-in-Time Recovery
• Errant transaction detection
• Different MySQL versions for each cluster
• Upgrading MySQL version of a cluster
• Monitor for replication delays
• Built-in mysqld_exporter for mysqld metrics
• Services for the primary and replicas, respectively
• Custom my.cnf configurations
• Custom Pod, Service, and PersistentVolumeClaim templates
• Redirect slow query logs to a sidecar container
• Auto-generate PodDisruptionBudget

You can quickly run MOCO using kind.

1. Prepare a Linux machine and install Docker.
2. Checkout MOCO and go to e2e directory.
3. Run make start

You can then create a three-instance MySQL cluster as follows:

$ cat > mycluster.yaml <<'EOF'
apiVersion: moco.cybozu.com/v1beta2
kind: MySQLCluster
metadata:
  namespace: default
  name: test
spec:
  replicas: 3
  podTemplate:
    spec:
      containers:
      - name: mysqld
        image: ghcr.io/cybozu-go/moco/mysql:8.0.35
  volumeClaimTemplates:
  - metadata:
      name: mysql-data
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 1Gi
EOF

$ export KUBECONFIG=$(pwd)/.kubeconfig
$ ../bin/kubectl apply -f mycluster.yaml

Check the status of MySQLCluster until it becomes healthy as follows:

$ ../bin/kubectl get mysqlcluster test
NAME   AVAILABLE   HEALTHY   PRIMARY   SYNCED REPLICAS   ERRANT REPLICAS
test   True        True      0         3

Once it becomes healthy, you can use kubectl-moco to play with mysql client.

$ ../bin/kubectl moco mysql -it test

To destroy the Kubernetes cluster, run:

$ make stop

See https://cybozu-go.github.io/moco/

examples directory contains example MySQLCluster manifests.

Docker images are available on ghcr.io/cybozu-go/moco.