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System Metadata Backup and Restore

Kylin instances are stateless services, and all state information is stored in metadata. Therefore, backing up and restoring metadata is a crucial part of operation and maintenance.

Metadata is divided into system level and project level.

Metadata Backup​

In general, it is a good practice to back up metadata before each failure recovery or system upgrade. This can guarantee the possibility of rollback after the operation fails, and still maintain the stability of the system in the worst case.

In addition, metadata backup is also a tool for fault finding. When the system fails, the frontend frequently reports errors. By downloading and viewing metadata, it is often helpful to determine whether there is a problem with the metadata or not.

Metadata can be backed up via the command line, as follows:

  • Metadata backup via command line

    Kylin provides a command line tool for backing up metadata, using the following methods:

    • Backup system level metadata

      $KYLIN_HOME/bin/metastore.sh backup METADATA_BACKUP_PATH

      Parameter Description:

      • METADATA_BACKUP_PATH - optional, represents the metadata storage path of the backup, the default value is ${KYLIN_HOME}/meta_backups/

    • Backup project level metadata

      $KYLIN_HOME/bin/metastore.sh backup-project PROJECT_NAME METADATA_BACKUP_PATH

      Parameter Description:

      • PROJECT_NAME - required, the name of the project to be backed up, such as learn_kylin
      • METADATA_BACKUP_PATH - optional, represents the metadata storage path of the backup, the default value is ${KYLIN_HOME}/meta_backups/

Metadata Restore​

Metadata recovery is required in Kylin with the command line.

  • Restore system level metadata

    $KYLIN_HOME/bin/metastore.sh restore METADATA_BACKUP_PATH [--after-truncate]

    Example:

    ./bin/metastore.sh restore meta_backups/2019-12-19-14-18-01_backup/

    Parameter Description:

    • METADATA_BACKUP_PATH - required, represents the metadata path that are going to be recovered, the default value is `${KYLIN_HOME}/meta_backups/
    • --after-truncate - optional, if this parameter is added, the system metadata will be completely restored, otherwise only the deleted and modified metadata will be restored, and the new metadata will still be retained.

  • Restore project level metadata 

    $KYLIN_HOME/bin/metastore.sh restore-project PROJECT_NAME METADATA_BACKUP_PATH [--after-truncate]

    Example:

    ./bin/metastore.sh restore-project projectA meta_backups/2019-12-19-14-18-01_backup/

    Parameter Description:

    • PROJECT_NAME - required, represents the project name
    • METADATA_BACKUP_PATH - required, represents the metadata path that are going to be recovered, the default value is `${KYLIN_HOME}/meta_backups/
    • --after-truncate - optional, if this parameter is added, the project metadata will be completely restored, otherwise only the deleted and modified metadata will be restored, and the new metadata will still be retained.

Caution When run this command, Kylin will enter maintenance mode. If the command is interrupted by force, you may need to exit maintain mode manually. Refer Maintenance Mode.