WL#3572: Online backup: No-data engine backup and restore
Affects: Server-6.0 — Status: Complete
Backup support is needed for engines that don't store any data, e.g.: - Federated engine support - Blackhole engine support - Example engine support - Merge engine support
These engines will not provide any backup image for data stored in tables. The task is to make them properly respond to backup/restore protocols used by the backup kernel. ON NEW ------ The driver is expected to respond 'TRUE' if the following engines are presented to the accept() method: case DB_TYPE_MRG_MYISAM: case DB_TYPE_BLACKHOLE_DB: case DB_TYPE_FEDERATED_DB: case DB_TYPE_EXAMPLE_DB: ON BACKUP --------- The kernel will send the following requests to a backup driver: - size, init_size Ask for total size of the image and for the size of initial data -- both should return 0. - begin, end Do nothing. - get_data Ask for next block of data. The driver should return one empty block (for stream 0) indicating end of the initial data transfer. If asked for further blocks of data, should always return empty block indicating end of stream. - prelock, lock, unlock Synchronization calls -- for no-data engines these should do nothing and return immediately. - cancel Do nothing. ON RESTORE ---------- A restore driver should be ready to receive these calls: - begin, end Do nothing. - send_data Any data sent should be simply ignored. A call should return ok answer. - cancel Do nothing. Changes to default driver (be_default) -------------------------------------- The default driver shall reject the storage engines listed above in its accept () method.
The nodata driver shall implement a class of type Snapshot_info which will provide the kernel a means to create a backup and restore driver class. The nodata backup and restore driver classes shall be implemented by inheriting from the Backup_driver and Restore_driver base classes. The methods supported for each shall be implemented as descibed above. The changes to the kernel are to be minimized and shall be limited to adding code to create a new instance of the nodata driver in the snapshot array for backup and adding identification of the nodata driver from the catalog on restore. get_data() ---------- The get_data() method for the backup driver class shall support the following modes: initialization, lock, and complete. There are no other modes needed and the method shall not open, lock, or read from any tables. send_data() ----------- The send_data() method for the restore driver class shall simply return and empty buffer. It does not open, lock, or write to any tables.
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