Use DM in Kubernetes

TiDB Data Migration (DM) is an integrated data migration task management platform that supports the full data migration and the incremental data replication from MySQL/MariaDB into TiDB. This document describes how to migrate MySQL data to TiDB cluster using DM in Kubernetes.

Prerequisites

• Complete deploying TiDB Operator.
• Complete deploying DM in Kubernetes.

Enable DM data migration tasks

You can access the DM-master service using dmctl in the following two methods:

Method #1: Attach to the DM-master or DM-worker Pod to use the built-in dmctl in the image.

Method #2: Expose the DM-master service by accessing the DM cluster in Kubernetes and use dmctl outside the pods to access the exposed DM-master service.

It is recommended to use Method #1 for migration. The following steps take Method #1 as an example to introduce how to start a DM data migration task.

The differences between Method #1 and Method #2 are that the file locations of source.yaml and task.yaml are different, and that in Method #2 you need to configure the exposed DM-master service address in the master-addr configuration item of dmctl.

Get into the Pod

Attach to the DM-master Pod by executing the following command:

kubectl exec -ti ${dm_cluster_name}-dm-master-0 -n ${namespace} -- /bin/sh

Create data source

1. Write MySQL-1 related information to source1.yaml file, which can refer to Create data source.

2. Configure the from.host in the source1.yaml file as the MySQL host address that the Kubernetes cluster can access internally.

3. Configure the relay-dir in the source1.yaml file as a subdirectory of the persistent volume in the Pod mount /var/lib/dm-worker directory. For example, /var/lib/dm-worker/relay.

4. After you prepare the source1.yaml file, load the MySQL-1 data source into the DM cluster by executing the following command:

   /dmctl --master-addr ${dm_cluster_name}-dm-master:8261 operate-source create source1.yaml
   

5. For MySQL-2 and other data sources, use the same method to modify the relevant information in the data source yaml file and execute the same dmctl command to load the corresponding data source into the DM cluster.

Configure migration tasks

1. Edit task configuration file task.yaml, which can refer to Configure the data migration task.

2. Configure the target-database.host in task.yaml as the TiDB host address that the Kubernetes cluster can access internally. If the cluster is deployed by TiDB Operator, configure the host as ${tidb_cluster_name}-tidb.${namespace}.

3. In the task.yaml file, take the following steps:

   • Add the loaders.${customized_name}.dir field as the import and export directory for the full volume data, where ${customized_name} is a name that you can customize.
   • Configure the loaders.${customized_name}.dir field as the subdirectory of the persistent volume in the Pod /var/lib/dm-worker directory. For example, /var/lib/dm-worker/dumped_data.
   • Reference ${customized_name} in the instance configuration. For example, mysql-instances[0].loader-config-name: "{customized_name}".

Start/Check/Stop the migration tasks

Refer to the corresponding steps in Migrate Data Using DM and fill in the master-addr as ${dm_cluster_name}-dm-master:8261.