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Import Data

This document describes how to import data into a TiDB cluster in Kubernetes using TiDB Lightning.

TiDB Lightning contains two components: tidb-lightning and tikv-importer. In Kubernetes, the tikv-importer is inside the separate Helm chart of the TiDB cluster. And tikv-importer is deployed as a StatefulSet with replicas=1 while tidb-lightning is in a separate Helm chart and deployed as a Job.

TiDB Lightning supports three backends: Importer-backend, Local-backend, and TiDB-backend. For the differences of these backends and how to choose backends, see TiDB Lightning Backends.

Deploy TiKV Importer

Note:

If you use the local or tidb backend for data restore, you can skip deploying tikv-importer and deploy tidb-lightning directly.

You can deploy tikv-importer using the Helm chart. See the following example:

  1. Make sure that the PingCAP Helm repository is up to date:

    helm repo update
    helm search repo tikv-importer -l
  2. Get the default values.yaml file for easier customization:

    helm inspect values pingcap/tikv-importer --version=${chart_version} > values.yaml
  3. Modify the values.yaml file to specify the target TiDB cluster. See the following example:

    clusterName: demo
    image: pingcap/tidb-lightning:v4.0.13
    imagePullPolicy: IfNotPresent
    storageClassName: local-storage
    storage: 20Gi
    pushgatewayImage: prom/pushgateway:v0.3.1
    pushgatewayImagePullPolicy: IfNotPresent
    config: |
      log-level = "info"
      [metric]
      job = "tikv-importer"
      interval = "15s"
      address = "localhost:9091"

    clusterName must match the target TiDB cluster.

    If the target TiDB cluster has enabled TLS between components (spec.tlsCluster.enabled: true), refer to Generate certificates for components of the TiDB cluster to genereate a server-side certificate for TiKV Importer, and configure tlsCluster.enabled: true in values.yaml to enable TLS.

  4. Deploy tikv-importer:

    helm install ${cluster_name} pingcap/tikv-importer --namespace=${namespace} --version=${chart_version} -f values.yaml

    Note:

    You must deploy tikv-importer in the same namespace where the target TiDB cluster is deployed.

Deploy TiDB Lightning

Configure TiDB Lightning

Use the following command to get the default configuration of TiDB Lightning:

helm inspect values pingcap/tidb-lightning --version=${chart_version} > tidb-lightning-values.yaml

Configure a backend used by TiDB Lightning depending on your needs. To do that, you can set the backend value in values.yaml to an option in importer, local, or tidb.

Note:

If you use the local backend, you must set sortedKV in values.yaml to create the corresponding PVC. The PVC is used for local KV sorting.

Starting from v1.1.10, the tidb-lightning Helm chart saves the TiDB Lightning checkpoint information in the directory of the source data. When the a new tidb-lightning job is running, it can resume the data import according to the checkpoint information.

For versions earlier than v1.1.10, you can modify config in values.yaml to save the checkpoint information in the target TiDB cluster, other MySQL-compatible databases or a shared storage directory. For more information, refer to TiDB Lightning checkpoint.

If TLS between components has been enabled on the target TiDB cluster (spec.tlsCluster.enabled: true), refer to Generate certificates for components of the TiDB cluster to genereate a server-side certificate for TiDB Lightning, and configure tlsCluster.enabled: true in values.yaml to enable TLS between components.

If the target TiDB cluster has enabled TLS for the MySQL client (spec.tidb.tlsClient.enabled: true), and the corresponding client-side certificate is configured (the Kubernetes Secret object is ${cluster_name}-tidb-client-secret), you can configure tlsClient.enabled: true in values.yaml to enable TiDB Lightning to connect to the TiDB server using TLS.

To use different client certificates to connect to the TiDB server, refer to Issue two sets of certificates for the TiDB cluster to generate the client-side certificate for TiDB Lightning, and configure the corresponding Kubernetes secret object in tlsCluster.tlsClientSecretName in values.yaml.

Note:

If TLS is enabled between components via tlsCluster.enabled: true but not enabled between TiDB Lightning and the TiDB server via tlsClient.enabled: true, you need to explicitly disable TLS between TiDB Lightning and the TiDB server in config in values.yaml:

[tidb]
tls="false"

TiDB Lightning Helm chart supports both local and remote data sources.

Local

In the local mode, the backup data must be on one of the Kubernetes node. To enable this mode, set dataSource.local.nodeName to the node name and dataSource.local.hostPath to the path of the backup data. The path should contain a file named metadata.

Remote

Unlike the local mode, the remote mode needs to use rclone to download the backup tarball file from a network storage to a PV. Any cloud storage supported by rclone should work, but currently only the following have been tested: Google Cloud Storage (GCS), Amazon S3, Ceph Object Storage.

To restore backup data from the remote source, take the following steps:

  1. Make sure that dataSource.local.nodeName and dataSource.local.hostPath in values.yaml are commented out.

  2. Grant permissions to the remote storage

    If you use Amazon S3 as the storage, refer to AWS account Permissions. The configuration varies with different methods.

    If you use Ceph as the storage, you can only grant permissions by importing AccessKey and SecretKey. See Grant permissions by AccessKey and SecretKey.

    If you use GCS as the storage, refer to GCS account permissions.

    • Grant permissions by importing AccessKey and SecretKey

      1. Create a Secret configuration file secret.yaml containing the rclone configuration. A sample configuration is listed below. Only one cloud storage configuration is required.

        apiVersion: v1
        kind: Secret
        metadata:
          name: cloud-storage-secret
        type: Opaque
        stringData:
          rclone.conf: |
            [s3]
            type = s3
            provider = AWS
            env_auth = false
            access_key_id = ${access_key}
            secret_access_key = ${secret_key}
            region = us-east-1
        
            [ceph]
            type = s3
            provider = Ceph
            env_auth = false
            access_key_id = ${access_key}
            secret_access_key = ${secret_key}
            endpoint = ${endpoint}
            region = :default-placement
        
            [gcs]
            type = google cloud storage
            # The service account must include Storage Object Viewer role
            # The content can be retrieved by `cat ${service-account-file} | jq -c .`
            service_account_credentials = ${service_account_json_file_content}
      2. Execute the following command to create Secret:

        kubectl apply -f secret.yaml -n ${namespace}
    • Grant permissions by associating IAM with Pod or with ServiceAccount

      If you use Amazon S3 as the storage, you can grant permissions by associating IAM with Pod or with ServiceAccount, in which s3.access_key_id and s3.secret_access_key can be ignored.

      1. Save the following configurations as secret.yaml.

        apiVersion: v1
        kind: Secret
        metadata:
          name: cloud-storage-secret
        type: Opaque
        stringData:
          rclone.conf: |
            [s3]
            type = s3
            provider = AWS
            env_auth = true
            access_key_id =
            secret_access_key =
            region = us-east-1
      2. Execute the following command to create Secret:

        kubectl apply -f secret.yaml -n ${namespace}
  3. Configure the dataSource.remote.storageClassName to an existing storage class in the Kubernetes cluster.

Ad hoc

When restoring data from remote storage, sometimes the restore process is interrupted due to the exception. In such cases, if you do not want to download backup data from the network storage repeatedly, you can use the ad hoc mode to directly recover the data that has been downloaded and decompressed into PV in the remote mode. The steps are as follows:

  1. Ensure dataSource.local and dataSource.remote in the config file values.yaml are empty。

  2. Configure dataSource.adhoc.pvcName in values.yaml to the PVC name used in restoring data from remote storage.

  3. Configure dataSource.adhoc.backupName in values.yaml to the name of the original backup data, such as: backup-2020-12-17T10:12:51Z (Do not contain the '. tgz' suffix of the compressed file name on network storage).

Deploy TiDB Lightning

The method of deploying TiDB Lightning varies with different methods of granting permissions and with different storages.

  • For Local Mode, Ad hoc Mode, and Remote Mode (only for remote modes that meet one of the three requirements: using Amazon S3 AccessKey and SecretKey permission granting methods, using Ceph as the storage backend, or using GCS as the storage backend), run the following command to deploy TiDB Lightning.

    helm install ${release_name} pingcap/tidb-lightning --namespace=${namespace} --set failFast=true -f tidb-lightning-values.yaml --version=${chart_version}
  • For Remote Mode, if you grant permissions by associating Amazon S3 IAM with Pod, take the following steps:

    1. Create the IAM role:

      Create an IAM role for the account, and grant the required permission to the role. The IAM role requires the AmazonS3FullAccess permission because TiDB Lightning needs to access Amazon S3 storage.

    2. Modify tidb-lightning-values.yaml, and add the iam.amazonaws.com/role: arn:aws:iam::123456789012:role/user annotation in the annotations field.

    3. Deploy TiDB Lightning:

      helm install ${release_name} pingcap/tidb-lightning --namespace=${namespace} --set failFast=true -f tidb-lightning-values.yaml --version=${chart_version}

      Note:

      arn:aws:iam::123456789012:role/user is the IAM role created in Step 1.

  • For Remote Mode, if you grant permissions by associating Amazon S3 with ServiceAccount, take the following steps:

    1. Enable the IAM role for the service account on the cluster:

      To enable the IAM role permission on the EKS cluster, see AWS Documentation.

    2. Create the IAM role:

      Create an IAM role. Grant the AmazonS3FullAccess permission to the role, and edit Trust relationships of the role.

    3. Associate IAM with the ServiceAccount resources:

      kubectl annotate sa ${servieaccount} -n eks.amazonaws.com/role-arn=arn:aws:iam::123456789012:role/user
    4. Deploy TiDB Lightning:

      helm install ${release_name} pingcap/tidb-lightning --namespace=${namespace} --set-string failFast=true,serviceAccount=${servieaccount} -f tidb-lightning-values.yaml --version=${chart_version}

      Note:

      arn:aws:iam::123456789012:role/user is the IAM role created in Step 1. ${service-account} is the ServiceAccount used by TiDB Lightning. The default value is default.

Destroy TiKV Importer and TiDB Lightning

Currently, TiDB Lightning only supports restoring data offline. After the restore, if the TiDB cluster needs to provide service for external applications, you can destroy TiDB Lightning to save cost.

To destroy tikv-importer, execute the following command:

helm uninstall ${release_name} -n ${namespace}

To destroy tidb-lightning, execute the following command:

helm uninstall ${release_name} -n ${namespace}

Troubleshoot TiDB Lightning

When TiDB Lightning fails to restore data, you cannot simply restart it. Manual intervention is required. Therefore, the TiDB Lightning's Job restart policy is set to Never.

Note:

If you have not configured to persist the checkpoint information in the target TiDB cluster, other MySQL-compatible databases or a shared storage directory, after the restore failure, you need to first delete the part of data already restored to the target cluster. After that, deploy tidb-lightning again and retry the data restore.

If TiDB Lightning fails to restore data, and if you have configured to persist the checkpoint information in the target TiDB cluster, other MySQL-compatible databases or a shared storage directory, follow the steps below to do manual intervention:

  1. View the log by executing the following command:

    kubectl logs -n ${namespace} ${pod_name}
    • If you restore data using the remote data source, and the error occurs when TiDB Lightning downloads data from remote storage:

      1. Address the problem according to the log.
      2. Deploy tidb-lightning again and retry the data restore.
    • For other cases, refer to the following steps.

  2. Refer to TiDB Lightning Troubleshooting and learn the solutions to different issues.

  3. Address the issues accordingly:

    • If tidb-lightning-ctl is required:

      1. Configure dataSource in values.yaml. Make sure the new Job uses the data source and checkpoint information of the failed Job:

        • In the local or ad hoc mode, you do not need to modify dataSource.
        • In the remote mode, modify dataSource to the ad hoc mode. dataSource.adhoc.pvcName is the PVC name created by the original Helm chart. dataSource.adhoc.backupName is the backup name of the data to be restored.
      2. Modify failFast in values.yaml to false, and create a Job used for tidb-lightning-ctl.

        • Based on the checkpoint information, TiDB Lightning checks whether the last data restore encountered an error. If yes, TiDB Lightning pauses the restore automatically.
        • TiDB Lightning uses the checkpoint information to avoid repeatedly restoring the same data. Therefore, creating the Job does not affect data correctness.
      3. After the Pod corresponding to the new Job is running, view the log by running kubectl logs -n ${namespace} ${pod_name} and confirm tidb-lightning in the new Job already stops data restore. If the log has the following message, the data restore is stopped:

        • tidb lightning encountered error
        • tidb lightning exit
      4. Enter the container by running kubectl exec -it -n ${namespace} ${pod_name} -it -- sh.

      5. Obtain the starting script by running cat /proc/1/cmdline.

      6. Get the command-line parameters from the starting script. Refer to TiDB Lightning Troubleshooting and troubleshoot using tidb-lightning-ctl.

      7. After the troubleshooting, modify failFast in values.yaml to true and create a new Job to resume data restore.

    • If tidb-lightning-ctl is not required:

      1. Troubleshoot TiDB Lightning.

      2. Configure dataSource in values.yaml. Make sure the new Job uses the data source and checkpoint information of the failed Job:

        • In the local or ad hoc mode, you do not need to modify dataSource.
        • In the remote mode, modify dataSource to the ad hoc mode. dataSource.adhoc.pvcName is the PVC name created by the original Helm chart. dataSource.adhoc.backupName is the backup name of the data to be restored.
      3. Create a new Job using the modified values.yaml file and resume data restore.

  4. After the troubleshooting and data restore is completed, delete the Jobs for data restore and troubleshooting.