Restoring ClickHouse Service Data

Scenarios

ClickHouse data restoration is required in the following scenarios: when data is unexpectedly modified or deleted and requires retrieval; when major ClickHouse operations (such as upgrades or significant adjustments) cause exceptions in system data or fail to achieve the expected result; when all modules fail and become unavailable; and when data is migrated to a new cluster.

ClickHouse service data restoration tasks can be created on FusionInsight Manager. The system supports manual data restoration only.

The ClickHouse backup and restoration functions cannot identify the service and structure relationships of objects such as ClickHouse tables, indexes, and views. When executing backup and restoration tasks, you need to manage unified restoration points based on service scenarios to ensure proper service running.

MRS clusters support multiple data path types for restoring ClickHouse service data.

• RemoteHDFS: indicates that data is restored from the HDFS directory of the standby cluster.

• OBS: indicates that data is restored from OBS.

Notes and Constraints

• MRS 3.1.0 or later supports this function.
• Data restoration can be performed only when the system version is consistent with the version used during data backup.
• ClickHouse metadata restoration and service data restoration cannot be performed simultaneously. Otherwise, service data restoration fails. You are advised to restore service data only after metadata restoration is complete.
• MRS 3.3.0-LTS.1 and later versions support the storage of ClickHouse service data backup files to OBS.

Impact on the System

• During data restoration, user authentication stops and users cannot create new connections.
• After the data is restored, the data generated after the data backup and before the data restoration is lost.
• After the data is restored, the ClickHouse upper-layer applications need to be started.

Prerequisites

• If you need to restore data from a remote HDFS, a standby cluster has been created and the data has been backed up. For details, see Backing Up ClickHouse Service Data. If the active and standby clusters are deployed in security mode and they are not managed by the same FusionInsight Manager, mutual trust has been configured. For details, see Configuring Mutual Trust Between MRS Clusters. If the active and standby clusters are deployed in normal mode, mutual trust is not required.

• Time is consistent between the active and standby clusters, with the NTP services on both clusters configured to use the same time source.
• The database for storing restored data tables, the HDFS save path of data tables, and the list of users who can access restored data are planned.
• The ClickHouse backup file save path is correct.
• The ClickHouse upper-layer applications are stopped.
• In an active/standby cluster, the value of HADOOP_RPC_PROTECTION of ClickHouse must be the same as that of hadoop.rpc.protection in the HDFS when you restore data from the remote HDFS to the local host.
• If the cluster to be restored does not contain the metadata of the backup service data, you must restore the corresponding backup metadata before restoring the service data, or restore both the backup metadata and backup service data simultaneously.
• To restore backup data from another MRS ClickHouse cluster to this cluster, the following requirements must be met:
  1. The two clusters are of the same MRS version.
  2. The two clusters are in the same mode.
  3. The two clusters share the same ClickHouse topology, including shards and replicas.
  4. The number of ClickHouse disk partitions and disk capacity of the cluster to be restored must be greater than or equal to those of the backup cluster.

Restoring ClickHouse Service Data

1. Log in to MRS Manager.

   For details about how to log in to MRS Manager, see Accessing MRS Manager.

2. Choose O&M > Backup and Restoration > Backup Management.
3. In the row containing the specified backup task, choose More > View History in the Operation column to display the task's historical execution records.

   In the displayed window, locate the desired success record and click View in the Backup Path column to display the task's backup path information and obtain the following details:

   • Backup Object: indicates the backup data source.
   • Backup Path: indicates the full path where the backup files are stored.

     Locate the correct path, and manually copy the full path of the backup files from the Backup Path column.

4. Choose O&M > Backup and Restoration > Restoration Management.
5. Click Create.
6. Set Task Name to the name of the restoration task.
7. Select the cluster to be operated from Recovery Object.
8. In Restoration Configuration, select ClickHouse under Service data.
9. Select a backup directory type for Path Type of ClickHouse.

   Table 1 Path for data restoration

   Path Type	Parameter	Description
   RemoteHDFS	Source NameService Name	NameService name of the backup data cluster. You can obtain it from the NameService Management page of HDFS in the standby cluster. For example, the name is hacluster.
   	IP Mode	IP version of the target IP address. The system automatically determines the IP version, such as IPv4 or IPv6, based on the cluster network type.
   	Source Active NameNode IP Address	Service plane IP address of the active NameNode in the standby cluster. Log in to MRS Manager of the standby cluster, choose Cluster > Services > HDFS, click the Instances tab, and check the service plane IP address of the active NameNode. This parameter is available for clusters of MRS 3.2.0 or later.
   	Source Standby NameNode IP Address	Service plane IP address of the standby NameNode in the standby cluster. Log in to MRS Manager of the standby cluster, choose Cluster > Services > HDFS, click the Instances tab, and check the service plane IP address of the standby NameNode. This parameter is available for clusters of MRS 3.2.0 or later.
   	Source NameNode IP Address	Service plane IP address of the active or standby NameNode in the standby cluster. Log in to MRS Manager of the standby cluster, choose Cluster > Services > HDFS, click the Instances tab, and check the service plane IP address of the NameNode. This parameter is available only for MRS 3.1.0 and MRS 3.1.2 clusters.
   	Source NameNode RPC Port	Value of dfs.namenode.rpc.port in the HDFS basic configuration of the destination cluster. This parameter is available for clusters of MRS 3.2.0 or later.
   	Source Path	Full path of the HDFS directory storing backup data in the standby cluster. For details, see Backup Path obtained in Step 3. Path format: Backup path/Backup task name_Data source_Task creation time
   	Maximum Number of Maps	Maximum number of maps in a MapReduce task. The default value is 20. This parameter is available only for MRS 3.1.0 and MRS 3.1.2 clusters.
   	Maximum Map Bandwidth (MB/s)	Maximum bandwidth of a map. The default value is 100. This parameter is available only for MRS 3.1.0 and MRS 3.1.2 clusters.
   	Restoration Point List	Click Refresh and select an HDFS directory that has already been backed up.
   	Concurrent Threads	Maximum number of concurrent threads for backing up data. The value ranges from 1 to 100. This parameter is available only for MRS 3.6.0 and later clusters.
   OBS	Source Path	Full path of the OBS directory storing backup files. Path format: Backup path/Backup task name_Data source_Task creation time/Version_Data source_Task execution time.tar.gz
   	Restoration Point List	Click Refresh and select an OBS directory that has already been backed up.
   	Concurrent Threads	Maximum number of concurrent threads for backing up data. The value ranges from 1 to 100.

10. For Recovery Content, select one or more ClickHouse tables to be restored.

    You can choose between two options for restoring your data:

    • Choose data files you want to restore

      Click the name of a database in the navigation pane to show all the tables in the database, and select specified tables.

      1. Click Add.
      2. In the File Directory box, select the table to be restored, and then click Add to move the table to the Restore Content box.
      3. Click OK to add the data file.
    • Selecting using regular expressions
      1. Click Query Regular Expression.
      2. Enter the database where the ClickHouse tables are located in the first text box as prompted. The database must be the same as the existing database, for example, /default_cluster/database.
      3. Enter a regular expression in the second text box. Standard regular expressions are supported. For example, to filter all tables that contain the keyword test in the database, enter test.*.
      4. Click Refresh to view the displayed tables in Directory Name.
      5. Click Synchronize to save the result.
      • When entering regular expressions, click or to add or delete an expression.
      • If the selected table or directory is incorrect, click Clear Selected Node to deselect it.

11. Click Verify to check whether the restoration task is configured correctly. (If no content is configured for restoration, skip this step.)

    The possible causes of the verification failure are as follows:

    • The target NameNode IP address is incorrect.
    • The directory or table to be backed up does not exist.
    • The name of the NameService is incorrect.

12. Click OK.
13. In the restoration task list, locate the row containing the created task, and click Start in the Operation column to execute the restoration task.
    • After the restoration is successful, the progress bar is in green.
    • After the restoration is successful, the restoration task cannot be executed again.
    • If the restoration task fails during the first execution, rectify the fault and click Retry to execute the task again.