How to use backups and asynchronous replication to move an external database to Kubernetes¶

The Operator enables you to restore a database from a backup made outside of Kubernetes environment to the target Kubernetes cluster using Percona XtraBackup . In such a way you can migrate your external database to Kubernetes. Using asyncronous replication between source and target environments enables you to reduce downtime and prevent data loss for your application.

This document provides the steps how to migrate Percona Server for MySQL 8.0 deployed on premises to the Kubernetes cluster managed by the Operator using asyncronous replication . We recommend testing this migration in a non-production environment first, before applying it in production.

Requirements¶

The MySQL version for source and target environments must be 8.0.22 and higher since asyncronous replication is available starting with MySQL version 8.0.22.
You must be running Percona XtraBackup as the backup tool on source environment. For how to install Percona XtraBackup, see the installation instructions
The storage used to save the backup should be one of the supported cloud storages: AWS S3 or compatible storage, or Azure Blob Storage.

Configure target environment¶

Deploy Percona Operator for MySQL and use it to create Percona XtraDB Cluster following any of the official installation guides.
Create the YAML file with the credentials for accessing the storage, needed to create the Kubernetes Secrets object. As and example here, we will use Amazon S3 storage. You will need to create a Secret with the following data to store backups on the Amazon S3:
- the metadata.name key is the name which you will further use to refer your Kubernetes Secret,
- the data.AWS_ACCESS_KEY_ID and data.AWS_SECRET_ACCESS_KEY keys are base64-encoded credentials used to access the storage (obviously these keys should contain proper values to make the access possible).
Create the Secrets file with these base64-encoded keys following the deploy/backup-s3.yaml example:
```
apiVersion: v1
kind: Secret
metadata:
  name: my-cluster-name-backup-s3
type: Opaque
data:
  AWS_ACCESS_KEY_ID: UkVQTEFDRS1XSVRILUFXUy1BQ0NFU1MtS0VZ
  AWS_SECRET_ACCESS_KEY: UkVQTEFDRS1XSVRILUFXUy1TRUNSRVQtS0VZ
```
Note

You can use the following command to get a base64-encoded string from a plain text one:
in Linuxin macOS
$ echo -n 'plain-text-string' | base64 --wrap=0
$ echo -n 'plain-text-string' | base64
Once the editing is over, create the Kubernetes Secret object as follows:
```
$ kubectl apply -f deploy/backup-s3.yaml
```
You will need passwords for the monitor, operator, xtrabackup and replication system users created by the Operator. Use kubectl get secrets command to see the list of Secrets objects (by default the Secrets object you are interested in has cluster1-secrets name). When you know the Secrets name, you can get password for a specfic user as follows:
```
$ kubectl get secrets cluster1-secrets --template='{{.data.<user_name> | base64decode}}{{"\n"}}'
```
Repeat this command 4 times, substituting with monitor, operator, xtrabackup and replication. You will further use these passwords when preparing the source environment.

Prepare the source environment¶

Use official installation instructions for either Percona Server for MySQL or Percona XtraDB Cluster to have the database up and running in your source environment (skip this step if one of them is already installed).
Use official installation instructions for Percona XtraBackup to have it up and running in your source environment (skip this step if it is already installed).
Configure the replication with Global Transaction Identifiers (GTID). This step is required if you are running Percona Sever for MySQL. If you run Percona XtraDB cluster, replication is already configured.

Edit the my.cnf configuration file as follows:
```
[mysqld]
enforce_gtid_consistency=ON
gtid_mode=ON
```

Create the monitor, operator, xtrabackup, and replication system users which will be needed by the Operator to restore a backup. User passwords must match the ones you have found out in your target environment.

Use the following commands to create users with the actual passwords instead of the monitor_password, operator_password, xtrabackup_password, and replication_password placeholders:

CREATE USER 'monitor'@'%' IDENTIFIED BY 'monitor_password' WITH MAX_USER_CONNECTIONS 100;
GRANT SELECT, PROCESS, SUPER, REPLICATION CLIENT, RELOAD ON *.* TO 'monitor'@'%';
GRANT SERVICE_CONNECTION_ADMIN ON *.* TO 'monitor'@'%';

CREATE USER 'operator'@'%' IDENTIFIED BY 'operator_password';
GRANT ALL ON *.* TO 'operator'@'%' WITH GRANT OPTION;

CREATE USER 'xtrabackup'@'%' IDENTIFIED BY 'xtrabackup_password';
GRANT ALL ON *.* TO 'xtrabackup'@'%';

CREATE USER 'replication'@'%' IDENTIFIED BY 'replication_password';
GRANT REPLICATION SLAVE ON *.* to 'replication'@'%';
FLUSH PRIVILEGES;

Make a backup in the source environment¶

Export the storage credentials as environment variables. Following the above example, here is a command which shows how to export the AWS S3 credentials:
```
$ export AWS_ACCESS_KEY_ID=XXXXXX
$ export AWS_SECRET_ACCESS_KEY=XXXXXX
```
Don’t forget to replace the XXXX placeholders with your actual Amazon access key ID and secret access key values.

Make the backup of your database and upload it to the storage using xbcloud . Replace the values for the --target-dir, --password, --s3-bucket with your values in the following command:

$ xtrabackup --backup --stream=xbstream --target-dir=/tmp/backups/ --extra-lsndir=/tmp/backups/  --password=root_password | xbcloud put --storage=s3 --parallel=10 --md5 --s3-bucket="mysql-testing-bucket" "db-test-1"

Restore from a backup in the target environment¶

If your source database didn’t have any data, skip this step and proceed with the asyncronous replication configuration. Otherwise, restore the database in the target environment.

To restore a backup, you will use the special restore configuration file. The example of such file is deploy/backup/restore.yaml . For example. your restore.yaml file may have the following contents:

restore.yaml

apiVersion: pxc.percona.com/v1
kind: PerconaXtraDBClusterRestore
metadata:
  name: restore1
spec:
  pxcCluster: cluster1
  backupSource:
    destination: s3://mysql-testing-bucket/db-test-1
    s3:
      credentialsSecret: my-cluster-name-backup-s3
      region: us-west-2

Don’t forget to replace the path to the backup and the credentials with your values.

Restore from the backup:
```
$ kubectl apply -f restore.yml
```

You can find more information on restoring backup to a new Kubernetes-based environment and see more examples in a dedicated HowTo.

Configure asyncronous replication in the Kubernetes cluster¶

This step will allow you to avoid data loss for your application, configuring the asyncronous replication between the source database and the target cluster.

Edit the Custom Resource manifest deploy/cr.yaml in your target environment to configure the spec.pxc.replicationChannels section.

cr.yaml

spec:
  ...
  pxc:
    ...
    replicationChannels:
    - name: ps_to_pxc1
      isSource: false
      sourcesList:
        - host: <source_ip>
          port: 3306
          weight: 100

Apply the changes for your Custom Resource as usual:

$ kubectl apply -f deploy/cr.yaml

Verify the replication by connecting to a Percona XtraDB Cluster node. You can do it with mysql tool, and you will need the root system user password created by the Operator for this. The password can be obtained in a same way we used for other system users:

$ kubectl get secrets cluster1-secrets -o yaml -o jsonpath='{.data.root}' | base64 --decode | tr '\n' ' ' && echo " "

When you know the root password, you can use kubectl command as follows (substitute root_password with the actual password you have just obtained):

$ kubectl exec -it cluster1-pxc-0 -c pxc -- mysql -uroot -proot_password -e "show replica status \G"

Expected output

*************************** 1. row ***************************
               Slave_IO_State: Waiting for master to send event
                  Master_Host: <ip-of-source-db>
                  Master_User: replication
                  Master_Port: 3306
                Connect_Retry: 60
              Master_Log_File: binlog.000004
          Read_Master_Log_Pos: 529
               Relay_Log_File: cluster1-pxc-0-relay-bin-ps_to_pxc1.000002
                Relay_Log_Pos: 738
        Relay_Master_Log_File: binlog.000004
             Slave_IO_Running: Yes
            Slave_SQL_Running: Yes
              Replicate_Do_DB:
          Replicate_Ignore_DB:
           Replicate_Do_Table:
       Replicate_Ignore_Table:
      Replicate_Wild_Do_Table:
  Replicate_Wild_Ignore_Table:
                   Last_Errno: 0
                   Last_Error:
                 Skip_Counter: 0
          Exec_Master_Log_Pos: 529
              Relay_Log_Space: 969
              Until_Condition: None
               Until_Log_File:
                Until_Log_Pos: 0
           Master_SSL_Allowed: No
           Master_SSL_CA_File:
           Master_SSL_CA_Path:
              Master_SSL_Cert:
            Master_SSL_Cipher:
               Master_SSL_Key:
        Seconds_Behind_Master: 0
Master_SSL_Verify_Server_Cert: No
                Last_IO_Errno: 0
                Last_IO_Error:
               Last_SQL_Errno: 0
               Last_SQL_Error:
  Replicate_Ignore_Server_Ids:
             Master_Server_Id: 1
                  Master_UUID: 9741945e-148d-11ec-89e9-5ee1a3cf433f
             Master_Info_File: mysql.slave_master_info
                    SQL_Delay: 0
          SQL_Remaining_Delay: NULL
      Slave_SQL_Running_State: Slave has read all relay log; waiting for more updates
           Master_Retry_Count: 3
                  Master_Bind:
      Last_IO_Error_Timestamp:
     Last_SQL_Error_Timestamp:
               Master_SSL_Crl:
           Master_SSL_Crlpath:
           Retrieved_Gtid_Set: 9741945e-148d-11ec-89e9-5ee1a3cf433f:1-2
            Executed_Gtid_Set: 93f1e7bf-1495-11ec-80b2-06e6016a7c3d:1,
9647dc03-1495-11ec-a385-7e3b2511dacb:1-7,
9741945e-148d-11ec-89e9-5ee1a3cf433f:1-2
                Auto_Position: 1
         Replicate_Rewrite_DB:
                 Channel_Name: ps_to_pxc1
           Master_TLS_Version:
       Master_public_key_path:
        Get_master_public_key: 0
            Network_Namespace:

Promote the Kubernetes cluster as primary¶

After you reconfigured your application to work with the new Percona XtraDB Cluster in Kubernetes, you can promote this cluster as primary.

Stop the replication. Edit the deploy/cr.yaml manifest and comment the replicationChannels subsection:

cr.yaml

...
spec:
  ...
  pxc:
    ...
    #replicationChannels:
    #- name: ps_to_pxc1
    #  isSource: false
    #  sourcesList:
    #    - host: <source_ip>
    #      port: 3306
    #      weight: 100

Stop the mysqld service in your source environment to make sure no new data is written:
```
$ sudo systemctl stop mysqld
```
Apply the changes to the Kubernetes cluster in your target environment:
```
$ kubectl apply -f deploy/cr.yaml
```

As a result, replication is stopped and the read-only mode is disabled for the Percona XtraDB Cluster.

This document is based on the blog post Migration of a MySQL Database to a Kubernetes Cluster Using Asynchronous Replication by Slava Sarzhan.

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Last update: 2024-12-19