Restoring Flink Metadata

Scenario

Flink metadata needs to be restored in the following scenarios: Data is modified or deleted unexpectedly and needs to be restored. After an administrator performs major operations (such as upgrade and data adjustment) on Flink, an exception occurs or the expected result is not achieved. The Flink component is faulty and becomes unavailable. Data is migrated to a new cluster.

System administrators can create a Flink restoration task on FusionInsight Manager. Only manual restoration tasks are supported.

• Data restoration can be performed only when the system version is consistent with that during data backup.
• To restore Flink metadata when the service is running properly, you are advised to manually back up the latest Flink metadata before restoration. Otherwise, the Flink metadata that is generated after the data backup and before the data restoration will be lost.
• Flink metadata restoration and service data restoration cannot be performed at the same time. Otherwise, service data restoration fails. You are advised to restore service data after metadata restoration is complete.

Impact on the System

• Before restoring the metadata, you need to stop the Flink service. During this period, all upper-layer applications are affected and cannot work properly.
• After the metadata is restored, the data generated after the data backup and before the data restoration is lost.
• After the metadata is restored, the Flink upper-layer applications of Solr need to be started.

Prerequisites

• You have checked the path for storing Flink metadata backup files.
• The Flink service has been stopped before its metadata is restored.
• 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 Flink Metadata. 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, no mutual trust is required.
• Cross-cluster replication has been configured for the active and standby clusters. For details, see Enabling MRS Inter-Cluster Replication.

Restoring Flink Metadata

1. On FusionInsight Manager, choose O&M > Backup and Restoration > Backup Management.
2. In the Operation column of the specified task in the task list, choose More > View History.

   In the displayed window, select a success record and click View in the Backup Path column to view its backup path information and find the following information:

   • Backup Object specifies the data source of the backup data.
   • Backup Path specifies the full path where the backup files are saved.

     Select the correct path, and manually copy the full path of backup files in Backup Path.

3. On FusionInsight Manager, choose O&M > Backup and Restoration > Restoration Management.
4. Click Create.
5. Set Task Name to the name of the restoration task.
6. Select the cluster to be operated from Recovery Object.
7. In Restoration Configuration, select Flink under Metadata and other data.
8. Set Path Type of Flink to a restoration directory type.

   The settings vary according to backup directory types:

   • LocalDir: indicates that data is restored from the local disk of the active management node.

     If you select LocalDir, you also need to set Source Path to select the backup file to be restored, for example, Backup task name_Data source_Task execution time.tar.gz.

   • LocalHDFS: indicates that the backup files are stored in the HDFS directory of the current cluster.
     If you select LocalHDFS, set the following parameters:

     • Source Path: indicates the full path of the backup file in the HDFS, for example, Backup path/Backup task name_Task creation time/Version_Data source_Task execution time.tar.gz.
     • Source NameService Name: indicates the NameService name that corresponds to the backup directory when a restoration task is executed.
   • RemoteHDFS: indicates that data is restored from the HDFS directory of the standby cluster.
     If you select RemoteHDFS, set the following parameters:

     • Source NameService Name: indicates the NameService name of the backup data cluster. You can enter the built-in NameService name of the remote cluster, for example, haclusterX, haclusterX1, haclusterX2, haclusterX3, or haclusterX4. You can also enter a configured NameService name of the remote cluster.
     • IP Mode: indicates the mode of the target IP address. The system automatically selects the IP address mode based on the cluster network type, for example, IPv4 or IPv6.
     • Source NameNode IP Address: indicates the NameNode service plane IP address of the standby cluster, supporting the active node or standby node.
     • Source Path: indicates the full path of HDFS directory for storing backup data of the standby cluster, for example, Backup path/Backup task name_Data source_Task creation time/Data source_Task execution time.tar.gz.
     • Queue Name: indicates the name of the Yarn queue used for backup task execution. The name must be the same as the name of the queue that is running properly in the source cluster.

9. Click OK.
10. In the restoration task list, locate the row where the created task is located, and click Start in the Operation column. In the displayed dialog box, click OK to start 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.

11. Choose Cluster > Services and start the Flink service.