Restoring CDL Service Data

Scenarios

CDL data restoration is required in the following scenarios: when data is unexpectedly modified or deleted and requires retrieval; when major CDL 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.

CDL metadata is stored in DBService and Kafka. You can create DBService and Kafka restoration tasks on FusionInsight Manager to restore CDL service data. The system supports manual data restoration only.

Data restoration can be performed only when the system version is consistent with the version used during data backup.
To restore data when the service is running properly, it is recommended that you manually back up the latest management data before performing data restoration. Otherwise, the DBService and Kafka data that is generated after the data backup and before the data restoration will be lost.
By default, MRS clusters use DBService to store metadata of Hive, Hue, Loader, Spark, CDL, and Oozie. Restoring DBService data will restore the metadata of all these components.

Impact on the System

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 configurations of the components that depend on DBService may expire and these components need to be restarted.
After the metadata is restored, the offset information stored on ZooKeeper by Kafka consumers is rolled back, resulting in repeated consumption.

Prerequisites

To restore data from a remote HDFS, the following conditions must be met:
- A standby cluster has been created for data restoration, and its data has been backed up. For details, see Backing Up CDL Service Data. If the active cluster is deployed in security mode and the active and standby clusters 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 cluster is deployed in normal mode, mutual trust is not required.
- Cross-cluster replication has been configured for the active and standby clusters. For details, see Enabling MRS Inter-Cluster Replication.
- Time is consistent between the active and standby clusters, with the NTP services on both clusters configured to use the same time source.

The status of the active and standby DBService instances is normal. If the status is abnormal, data restoration cannot be performed.

The Kafka service has been stopped. After the restoration is complete, start the Kafka service.

Restoring CDL Service Data

Log in to MRS Manager.

For details about how to log in to MRS Manager, see Accessing MRS Manager.
Choose O&M > Backup and Restoration > Backup Management.
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.
On FusionInsight Manager, choose O&M > Backup and Restoration > Restoration Management.
Click Create.
Set Task Name to the name of the restoration task.
Select the cluster to be operated from Recovery Object.
In the Restoration Configuration area, select DBService and Kafka.
Select a backup directory type for Path Type of DBService. For details about how to configure the parameters, see Step 9.
Select a backup directory type for Path Type of Kafka. For details about how to configure the parameters, see Step 9.
Click OK.
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.