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Horizontal Scale MySQL Group Replication
This guide will show you how to use KubeDB enterprise operator to increase/decrease the number of members of a MySQL Group Replication.
Before You Begin
At first, you need to have a Kubernetes cluster, and the
kubectlcommand-line tool must be configured to communicate with your cluster. If you do not already have a cluster, you can create one by using kind.Install
KubeDBcommunity and enterprise operator in your cluster following the steps here.You should be familiar with the following
KubeDBconcepts:
To keep everything isolated, we are going to use a separate namespace called demo throughout this tutorial.
$ kubectl create ns demo
namespace/demo created
Note: YAML files used in this tutorial are stored in docs/guides/mysql/scaling/horizontal-scaling/group-replication/yamls directory of kubedb/doc repository.
Apply Horizontal Scaling on MySQL Group Replication
Here, we are going to deploy a MySQL group replication using a supported version by KubeDB operator. Then we are going to apply horizontal scaling on it.
Prepare Group Replication
At first, we are going to deploy a group replication server with 3 members. Then, we are going to add two additional members through horizontal scaling. Finally, we will remove 1 member from the cluster again via horizontal scaling.
Find supported MySQL Version:
When you have installed KubeDB, it has created MySQLVersion CR for all supported MySQL versions. Let’s check the supported MySQL versions,
$ kubectl get mysqlversion
NAME VERSION DB_IMAGE DEPRECATED AGE
5.7.25-v2 5.7.25 kubedb/mysql:5.7.25-v2 3h55m
5.7.36 5.7.29 kubedb/mysql:5.7.36 3h55m
5.7.36 5.7.31 kubedb/mysql:5.7.36 3h55m
5.7.36 5.7.33 kubedb/mysql:5.7.36 3h55m
8.0.14-v2 8.0.14 kubedb/mysql:8.0.14-v2 3h55m
8.0.20-v1 8.0.20 kubedb/mysql:8.0.20-v1 3h55m
8.0.27 8.0.21 kubedb/mysql:8.0.27 3h55m
8.0.27 8.0.27 kubedb/mysql:8.0.27 3h55m
8.0.3-v2 8.0.3 kubedb/mysql:8.0.3-v2 3h55m
The version above that does not show DEPRECATED true is supported by KubeDB for MySQL. You can use any non-deprecated version. Here, we are going to create a MySQL Group Replication using MySQL 8.0.27.
Deploy MySQL Group Replication:
In this section, we are going to deploy a MySQL group replication with 3 members. Then, in the next section we will scale-up the cluster using horizontal scaling. Below is the YAML of the MySQL cr that we are going to create,
apiVersion: kubedb.com/v1alpha2
kind: MySQL
metadata:
name: my-group
namespace: demo
spec:
version: "8.0.27"
replicas: 3
topology:
mode: GroupReplication
group:
name: "dc002fc3-c412-4d18-b1d4-66c1fbfbbc9b"
storageType: Durable
storage:
storageClassName: "standard"
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 1Gi
terminationPolicy: WipeOut
Let’s create the MySQL cr we have shown above,
$ kubectl create -f https://github.com/kubedb/docs/raw/v2021.12.21/docs/guides/mysql/scaling/horizontal-scaling/group-replication/yamls/group-replication.yaml
mysql.kubedb.com/my-group created
Wait for the cluster to be ready:
KubeDB operator watches for MySQL objects using Kubernetes API. When a MySQL object is created, KubeDB operator will create a new StatefulSet, Services, and Secrets, etc. A secret called my-group-auth (format: {mysql-object-name}-auth) will be created storing the password for mysql superuser.
Now, watch MySQL is going to Running state and also watch StatefulSet and its pod is created and going to Running state,
$ watch -n 3 kubectl get my -n demo my-group
Every 3.0s: kubectl get my -n demo my-group suaas-appscode: Tue Jun 30 22:43:57 2020
NAME VERSION STATUS AGE
my-group 8.0.27 Running 16m
$ watch -n 3 kubectl get sts -n demo my-group
Every 3.0s: kubectl get sts -n demo my-group Every 3.0s: kubectl get sts -n demo my-group suaas-appscode: Tue Jun 30 22:44:35 2020
NAME READY AGE
my-group 3/3 16m
$ watch -n 3 kubectl get pod -n demo -l app.kubernetes.io/name=mysqls.kubedb.com,app.kubernetes.io/instance=my-group
Every 3.0s: kubectl get pod -n demo -l app.kubernetes.io/name=mysqls.kubedb.com suaas-appscode: Tue Jun 30 22:45:33 2020
NAME READY STATUS RESTARTS AGE
my-group-0 2/2 Running 0 17m
my-group-1 2/2 Running 0 14m
my-group-2 2/2 Running 0 11m
Let’s verify that the StatefulSet’s pods have joined into a group replication cluster,
$ kubectl get secrets -n demo my-group-auth -o jsonpath='{.data.\username}' | base64 -d
root
$ kubectl get secrets -n demo my-group-auth -o jsonpath='{.data.\password}' | base64 -d
sWfUMoqRpOJyomgb
$ kubectl exec -it -n demo my-group-0 -c mysql -- mysql -u root --password=sWfUMoqRpOJyomgb --host=my-group-0.my-group-gvr.demo -e "select * from performance_schema.replication_group_members"
mysql: [Warning] Using a password on the command line interface can be insecure.
+---------------------------+--------------------------------------+------------------------------+-------------+--------------+-------------+----------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE | MEMBER_ROLE | MEMBER_VERSION |
+---------------------------+--------------------------------------+------------------------------+-------------+--------------+-------------+----------------+
| group_replication_applier | 596be47b-baef-11ea-859a-02c946ef4fe7 | my-group-1.my-group-gvr.demo | 3306 | ONLINE | SECONDARY | 8.0.23 |
| group_replication_applier | 815974c2-baef-11ea-bd7e-a695cbdbd6cc | my-group-2.my-group-gvr.demo | 3306 | ONLINE | SECONDARY | 8.0.23 |
| group_replication_applier | ec61cef2-baee-11ea-adb0-9a02630bae5d | my-group-0.my-group-gvr.demo | 3306 | ONLINE | PRIMARY | 8.0.23 |
+---------------------------+--------------------------------------+------------------------------+-------------+--------------+-------------+----------------+
So, we can see that our group replication cluster has 3 members. Now, we are ready to apply the horizontal scale to this group replication.
Scale Up
Here, we are going to add 2 members in our group replication using horizontal scaling.
Create MySQLOpsRequest:
To scale up your cluster, you have to create a MySQLOpsRequest cr with your desired number of members after scaling. Below is the YAML of the MySQLOpsRequest cr that we are going to create,
apiVersion: ops.kubedb.com/v1alpha1
kind: MySQLOpsRequest
metadata:
name: my-scale-up
namespace: demo
spec:
type: HorizontalScaling
databaseRef:
name: my-group
horizontalScaling:
member: 5
Here,
spec.databaseRef.namespecifies that we are performing operation onmy-groupMySQLdatabase.spec.typespecifies that we are performingHorizontalScalingon our database.spec.horizontalScaling.memberspecifies the expected number of members after the scaling.
Let’s create the MySQLOpsRequest cr we have shown above,
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.12.21/docs/guides/mysql/scaling/horizontal-scaling/group-replication/yamls/scale_up.yaml
mysqlopsrequest.ops.kubedb.com/my-scale-up created
Verify Scale-Up Succeeded:
If everything goes well, KubeDB enterprise operator will scale up the StatefulSet’s Pod. After the scaling process is completed successfully, the KubeDB enterprise operator updates the replicas of the MySQL object.
First, we will wait for MySQLOpsRequest to be successful. Run the following command to watch MySQlOpsRequest cr,
Every 3.0s: kubectl get myops -n demo my-scale-up suaas-appscode: Sat Jul 25 15:49:42 2020
NAME TYPE STATUS AGE
my-scale-up HorizontalScaling Successful 2m55s
You can see from the above output that the MySQLOpsRequest has succeeded. If we describe the MySQLOpsRequest, we shall see that the MySQL group replication is scaled up.
$ kubectl describe myops -n demo my-scale-up
$ Name: my-scale-up
Namespace: demo
Labels: <none>
Annotations: <none>
API Version: ops.kubedb.com/v1alpha1
Kind: MySQLOpsRequest
Metadata:
Creation Timestamp: 2021-03-10T11:18:39Z
Generation: 2
Manager: kubedb-enterprise
Operation: Update
Time: 2021-03-10T11:20:45Z
Resource Version: 1088850
Self Link: /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mysqlopsrequests/my-scale-up
UID: f60f5bbc-3086-4b86-bf74-baf0b39ff358
Spec:
Database Ref:
Name: my-group
Horizontal Scaling:
Member: 5
Stateful Set Ordinal: 0
Type: HorizontalScaling
Status:
Conditions:
Last Transition Time: 2021-03-10T11:18:39Z
Message: Controller has started to Progress the MySQLOpsRequest: demo/my-scale-up
Observed Generation: 2
Reason: OpsRequestProgressingStarted
Status: True
Type: Progressing
Last Transition Time: 2021-03-10T11:18:40Z
Message: Horizontal scaling started in MySQL: demo/my-group for MySQLOpsRequest: my-scale-up
Observed Generation: 2
Reason: HorizontalScalingStarted
Status: True
Type: Scaling
Last Transition Time: 2021-03-10T11:20:45Z
Message: Horizontal scaling Up performed successfully in MySQL: demo/my-group for MySQLOpsRequest: my-scale-up
Observed Generation: 2
Reason: SuccessfullyPerformedHorizontalScaling
Status: True
Type: ScalingUp
Last Transition Time: 2021-03-10T11:20:45Z
Message: Controller has successfully scaled the MySQL demo/my-scale-up
Observed Generation: 2
Reason: OpsRequestProcessedSuccessfully
Status: True
Type: Successful
Observed Generation: 3
Phase: Successful
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Starting 28m KubeDB Enterprise Operator Start processing for MySQLOpsRequest: demo/my-scale-up
Normal Starting 28m KubeDB Enterprise Operator Pausing MySQL databse: demo/my-group
Normal Successful 28m KubeDB Enterprise Operator Successfully paused MySQL database: demo/my-group for MySQLOpsRequest: my-scale-up
Normal Starting 28m KubeDB Enterprise Operator Horizontal scaling started in MySQL: demo/my-group for MySQLOpsRequest: my-scale-up
Normal Successful 26m KubeDB Enterprise Operator Horizontal scaling Up performed successfully in MySQL: demo/my-group for MySQLOpsRequest: my-scale-up
Normal Starting 26m KubeDB Enterprise Operator Resuming MySQL database: demo/my-group
Normal Successful 26m KubeDB Enterprise Operator Successfully resumed MySQL database: demo/my-group
Normal Successful 26m KubeDB Enterprise Operator Controller has Successfully scaled the MySQL database: demo/my-group
Now, we are going to verify whether the number of members has increased to meet up the desired state, Let’s check,
$ kubectl get secrets -n demo my-group-auth -o jsonpath='{.data.\username}' | base64 -d
root
$ kubectl get secrets -n demo my-group-auth -o jsonpath='{.data.\password}' | base64 -d
Y28qkWFQ8QHVzq2h
$ kubectl exec -it -n demo my-group-0 -c mysql -- mysql -u root --password=Y28qkWFQ8QHVzq2h --host=my-group-0.my-group-gvr.demo -e "select * from performance_schema.replication_group_members"
mysql: [Warning] Using a password on the command line interface can be insecure.
+---------------------------+--------------------------------------+------------------------------+-------------+--------------+-------------+----------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE | MEMBER_ROLE | MEMBER_VERSION |
+---------------------------+--------------------------------------+------------------------------+-------------+--------------+-------------+----------------+
| group_replication_applier | 4b76f5c8-baff-11ea-9848-425294afbbbf | my-group-3.my-group-gvr.demo | 3306 | ONLINE | SECONDARY | 8.0.23 |
| group_replication_applier | 73c1f150-baff-11ea-9394-4a8c424ea5c2 | my-group-4.my-group-gvr.demo | 3306 | ONLINE | SECONDARY | 8.0.23 |
| group_replication_applier | 9f6c694c-bafd-11ea-8ad4-822669614bde | my-group-0.my-group-gvr.demo | 3306 | ONLINE | PRIMARY | 8.0.23 |
| group_replication_applier | c9d82f09-bafd-11ea-ab3a-764d326534a6 | my-group-1.my-group-gvr.demo | 3306 | ONLINE | SECONDARY | 8.0.23 |
| group_replication_applier | eff81073-bafd-11ea-9f3d-ca1e99c33106 | my-group-2.my-group-gvr.demo | 3306 | ONLINE | SECONDARY | 8.0.23 |
+---------------------------+--------------------------------------+------------------------------+-------------+--------------+-------------+----------------+
You can see above that our MySQL group replication now has a total of 5 members. It verifies that we have successfully scaled up.
Scale Down
Here, we are going to remove 1 member from our group replication using horizontal scaling.
Create MysQLOpsRequest:
To scale down your cluster, you have to create a MySQLOpsRequest cr with your desired number of members after scaling. Below is the YAML of the MySQLOpsRequest cr that we are going to create,
apiVersion: ops.kubedb.com/v1alpha1
kind: MySQLOpsRequest
metadata:
name: my-scale-down
namespace: demo
spec:
type: HorizontalScaling
databaseRef:
name: my-group
horizontalScaling:
member: 4
Let’s create the MySQLOpsRequest cr we have shown above,
$ kubectl apply -f https://github.com/kubedb/docs/raw/v2021.12.21/docs/guides/mysql/scaling/horizontal-scaling/group-replication/yamls/scale_down.yaml
mysqlopsrequest.ops.kubedb.com/my-scale-down created
Verify Scale-down Succeeded:
If everything goes well, KubeDB enterprise operator will scale down the StatefulSet’s Pod. After the scaling process is completed successfully, the KubeDB enterprise operator updates the replicas of the MySQL object.
Now, we will wait for MySQLOpsRequest to be successful. Run the following command to watch MySQlOpsRequest cr,
Every 3.0s: kubectl get myops -n demo my-scale-down suaas-appscode: Sat Jul 25 15:49:42 2020
NAME TYPE STATUS AGE
my-scale-down HorizontalScaling Successful 2m55s
You can see from the above output that the MySQLOpsRequest has succeeded. If we describe the MySQLOpsRequest, we shall see that the MySQL group replication is scaled down.
$ kubectl describe myops -n demo my-scale-down
Name: my-scale-down
Namespace: demo
Labels: <none>
Annotations: <none>
API Version: ops.kubedb.com/v1alpha1
Kind: MySQLOpsRequest
Metadata:
Creation Timestamp: 2021-03-10T11:48:42Z
Generation: 2
Manager: kubedb-enterprise
Operation: Update
Time: 2021-03-10T11:49:18Z
Resource Version: 1094487
Self Link: /apis/ops.kubedb.com/v1alpha1/namespaces/demo/mysqlopsrequests/my-scale-down
UID: 7b9471ed-87b1-4c62-939b-dbb8a7641554
Spec:
Database Ref:
Name: my-group
Horizontal Scaling:
Member: 4
Stateful Set Ordinal: 0
Type: HorizontalScaling
Status:
Conditions:
Last Transition Time: 2021-03-10T11:48:42Z
Message: Controller has started to Progress the MySQLOpsRequest: demo/my-scale-down
Observed Generation: 2
Reason: OpsRequestProgressingStarted
Status: True
Type: Progressing
Last Transition Time: 2021-03-10T11:48:43Z
Message: Horizontal scaling started in MySQL: demo/my-group for MySQLOpsRequest: my-scale-down
Observed Generation: 2
Reason: HorizontalScalingStarted
Status: True
Type: Scaling
Last Transition Time: 2021-03-10T11:49:18Z
Message: Horizontal scaling down performed successfully in MySQL: demo/my-group for MySQLOpsRequest: my-scale-down
Observed Generation: 2
Reason: SuccessfullyPerformedHorizontalScaling
Status: True
Type: ScalingDown
Last Transition Time: 2021-03-10T11:49:18Z
Message: Controller has successfully scaled the MySQL demo/my-scale-down
Observed Generation: 2
Reason: OpsRequestProcessedSuccessfully
Status: True
Type: Successful
Observed Generation: 4
Phase: Successful
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Starting 97s KubeDB Enterprise Operator Start processing for MySQLOpsRequest: demo/my-scale-down
Normal Starting 97s KubeDB Enterprise Operator Pausing MySQL databse: demo/my-group
Normal Successful 97s KubeDB Enterprise Operator Successfully paused MySQL database: demo/my-group for MySQLOpsRequest: my-scale-down
Normal Starting 96s KubeDB Enterprise Operator Horizontal scaling started in MySQL: demo/my-group for MySQLOpsRequest: my-scale-down
Normal Successful 61s KubeDB Enterprise Operator Horizontal scaling down performed successfully in MySQL: demo/my-group for MySQLOpsRequest: my-scale-down
Normal Starting 61s KubeDB Enterprise Operator Resuming MySQL database: demo/my-group
Normal Successful 61s KubeDB Enterprise Operator Successfully resumed MySQL database: demo/my-group
Normal Successful 61s KubeDB Enterprise Operator Controller has Successfully scaled the MySQL database: demo/my-group
Now, we are going to verify whether the number of members has decreased to meet up the desired state, Let’s check,
$ kubectl get secrets -n demo my-group-auth -o jsonpath='{.data.\username}' | base64 -d
root
$ kubectl get secrets -n demo my-group-auth -o jsonpath='{.data.\password}' | base64 -d
Y28qkWFQ8QHVzq2h
$ kubectl exec -it -n demo my-group-0 -c mysql -- mysql -u root --password=5pwciRRUWHhSJ6qQ --host=my-group-0.my-group-gvr.demo -e "select * from performance_schema.replication_group_members"
mysql: [Warning] Using a password on the command line interface can be insecure.
+---------------------------+--------------------------------------+------------------------------+-------------+--------------+-------------+----------------+
| CHANNEL_NAME | MEMBER_ID | MEMBER_HOST | MEMBER_PORT | MEMBER_STATE | MEMBER_ROLE | MEMBER_VERSION |
+---------------------------+--------------------------------------+------------------------------+-------------+--------------+-------------+----------------+
| group_replication_applier | 533602d0-ce5b-11ea-b866-5ad2598e5303 | my-group-1.my-group-gvr.demo | 3306 | ONLINE | SECONDARY | 8.0.23 |
| group_replication_applier | 7d429240-ce5b-11ea-9fe2-0aaa5a845ec8 | my-group-2.my-group-gvr.demo | 3306 | ONLINE | SECONDARY | 8.0.23 |
| group_replication_applier | c498302f-ce5b-11ea-96a3-72980d437abc | my-group-3.my-group-gvr.demo | 3306 | ONLINE | SECONDARY | 8.0.23 |
| group_replication_applier | dfb1633a-ce5a-11ea-a9c8-6e4ef86119d0 | my-group-0.my-group-gvr.demo | 3306 | ONLINE | PRIMARY | 8.0.23 |
+---------------------------+--------------------------------------+------------------------------+-------------+--------------+-------------+----------------+
You can see above that our MySQL group replication now has a total of 4 members. It verifies that we have successfully scaled down.
Cleaning Up
To clean up the Kubernetes resources created by this tutorial, run:
kubectl delete my -n demo my-group
kubectl delete myops -n demo my-scale-up
kubectl delete myops -n demo my-scale-down