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The following SQL statements will be introduced: BACKUP SERVER TO '/path/to/directory' [ 1 CONCURRENT ]; BACKUP SERVER WITH [ 1 CONCURRENT ] 'command'; In place of the 1, any positive number of threads may be specified. For the first variant, '/path/to' must exist and '/path/to/directory' must not exist; that is where the backup will be written to. For BACKUP SERVER WITH, the string mariadb-backup- will be prepended to the specified command and quoted. Path separators or quotes are not allowed in command. We expect the mariadb-backup-command to be in the search PATH of the mariadbd process. For now, we distribute no such script or program; the user has to write one, something like this: exec zstdmt|ssh backup@remote.example.com "exec cat > $1.tar.zstd" The standard input of that command will be in a format compatible with GNU tar --format=oldgnu (and also BSD tar variants that are also part of Microsoft Windows and Apple macOS). The command is expected to optionally compress and encrypt the stream and redirect it to a file on a local or a remote server. The BACKUP SERVER WITH will append an additional argument, a positive base-ten number in ASCII, starting with 1, to identify the current thread. In this way, there can be multiple concurrent streams. The InnoDB write-ahead log will be streamed near the end, because the stream format requires the file sizes to be declared upfront. TODO: implement the following: In BACKUP SERVER TO ... 2 CONCURRENT or more, one thread will be responsible for copying the InnoDB write-ahead log from the beginning of the backup. Other files will be copied by other threads. Note: In single-threaded BACKUP SERVER TO, the parameter innodb_log_recovery_start that is written out to backup.cnf is STRICTLY NECESSARY TO AVOID CORRUPTION during recovery! By default, InnoDB crash recovery starts from the latest available log checkpoint. However, for restoring a backup, recovery must start from the checkpoint that was the latest when the backup was started. Starting recovery from a possible later checkpoint will result in a corrupted database! The backup or the first stream will contain a file backup.cnf, which includes parameters needed for restoring the backup. Currently, these are innodb_log_recovery_start and innodb_log_recovery_target. If innodb_log_recovery_target>0, InnoDB will be in read-only mode, not allowing any writes to persistent files other than via the log application. To restore a streaming backup made with BACKUP SERVER WITH, an empty directory needs to be created and all streams be extracted there using the standard tar utility of the operating system, optionally after undoing any encryption or compression that had been added by the backup command. Then, the backup is prepared or MariaDB server started up on the extracted directory, similar to as if the BACKUP SERVER TO statement had been used. The following will be implemented separately: MDEV-39061 mariadb-backup compatible wrapper script for BACKUP SERVER MDEV-40163 Partial backup and restore MDEV-39091 Back up ENGINE=RocksDB MDEV-40333 Concurrent DDL for Aria tables in BACKUP SERVER The implementation introduces a basic multi-threaded driver Sql_cmd_backup, storage engine interfaces, and basic copying of the storage engines InnoDB, Aria, MyISAM, MERGE (MyISAM), Archive, CSV. backup_target: A structured data type to represent a target directory. On Microsoft Windows, we must use directory paths because there is no variant of CopyFileEx() that would work on file handles. backup_sink: Wraps a per-thread output stream as well as storage engine specific context. handlerton::backup_start(), handlerton::backup_end(): Invoked at the start or end of a backup phase, in the thread that executes a BACKUP SERVER statement. handlerton::backup_step(): A backup step that can be invoked from multiple threads concurrently, between the execution of the corresponding handlerton::backup_start() and handlerton::backup_end() of the same phase. copy_entire_file(): A file copying service for POSIX systems. copy_mmap(): A zero-copy alternative to backup::copy(), to copy from a memory-mapped buffer. copy_file_range_try(): A wrapper for Linux copy_file_range(2), which may fail with EOPNOTSUPP or EXDEV and thus require a fallback to copy_mmap() or backup::copy(). backup::copy(): A partial or sparse file-copying service. On other platforms than FreeBSD or Microsoft Windows, there are shortcut alternatives to this. Note: On Linux we never invoke sendfile(2) for copying between files, because can be much slower than the alternatives. backup_stream_append_plain(): A wrapper of backup::append(), which is the streaming equivalent of backup::copy(). backup_stream_zeropad(): Zero-pad the last tar block if needed. backup_stream_append_async(): A variant of backup_stream_append_plain() where the source file region is guaranteed to be immutable after the call returns. Zero-copy mmap(2) or Linux sendfile(2) are inherently risky for copying data files that may be modified in place, because it could introduce a race condition between a page write that runs concurrently with a child process that is reading the data from the pipe. backup::append(): On systems where we can determine the size of the pipe buffer, invoke backup_stream_append_async() for the initial write, and pread_write() for the last part, to guarantee that the data written by the zero-copy shortcut will have been consumed before the call returns and the caller is able to resume writes to the source region. pread_write(): On 64-bit systems, allocate a buffer of up to 1 MiB. This is the "slow path" of copying or streaming files. struct Aria_backup: Context for multi-threaded backup, comprising directory handles, a mutex and enum Aria_backup_status. aria_backup_start(): Prepare the context for aria_backup_step(). Most files are copied in BACKUP_PHASE_NO_DDL after flush_tables(thd, FLUSH_NON_TRANS_TABLES) has been invoked. All ENGINE=Aria files (including TRANSACTIONAL=0) are copied in BACKUP_PHASE_NO_COMMIT. Thanks to Andrzej Jarząbek for writing test cases and suggesting this logic. aria_backup_step(): Copy one non-ACID file. Acquires Aria_backup::mutex, traverses directories to construct one file name, releases the mutex, and copies the file if one was found. aria_backup_data(): Copy one data file. On Microsoft Windows, this assumes that the current directory is the datadir. This assumption would not hold in the Embedded Server library, which is not supported on Microsoft Windows. aria_backup_log(): Copy one ENGINE=Aria log file. aria_backup_end(): Finish a copying phase and clean up the context. InnoDB_backup::init(): Wait for a possible previous BACKUP SERVER operation to reach the very end of InnoDB_backup::context::cleanup() so that the context can be safely reused. InnoDB_backup::queue: Collection of tablespace IDs and payload sizes at the start of the backup, and the log_sys.first_lsn of log files that have to be included in the backup. If any data file is created or extended while the backup is executing, we must have the corresponding write-ahead-log entries that we are copying since the latest checkpoint that was completed when the backup started. If any tablespaces are deleted during the backup, we may or may not copy them, and the application of a FILE_DELETE record will remove them. Similarly, applying FILE_RENAME or FILE_CREATE records will rename or create files during recovery as needed. log_sys.backup: Whether BACKUP SERVER is in progress. The purpose of this is to make BACKUP SERVER prevent the concurrent execution of SET GLOBAL innodb_log_archive=OFF or SET GLOBAL innodb_log_file_size when innodb_log_archive=OFF. log_sys.archived_checkpoint: Keep track of the earliest available checkpoint, corresponding to log_sys.archived_lsn. This reflects SET GLOBAL innodb_log_recovery_start (which is settable now), for incremental backup. fil_system.have_all_spaces: Whether all tablespace metadata is guaranteed to be known. To speed up startup, InnoDB does not normally open all tablespace files. fil_space_t::create_lsn: Change to Atomic_relaxed and use this to indicate tablespace creation LSN, in addition to indicate undo tablespace rebuild LSN. fil_space_t::backup_end: The first page number that is not being backed up (by default 0, to indicate that no backup is in progress). fil_space_t::BACKUP_BATCH_SIZE: The number of preceding pages that will be covered by fil_space_t::backup_end. This is the unit of "page range locking" during InnoDB backup. buf_page_t::write_fix_try(), buf_page_t::write_unfix_try(): Try to set or unset a fake "write fix" on a page, to prevent concurrent flush() during a backup batch. The atomic operations may run concurrently with set_reinit() and set_freed(). The fake "write fix" does not prevent any concurrent read or write of the page data in the buffer pool; it only blocks writes to the underlying data file. buf_page_t::flush(): Atomically test and set write fix, and skip the operation if the fake "write fix" was set. buf_page_t::set_freed(), buf_page_t::set_reinit(): Employ a compare-and-exchange loop to accommodate for the "write fix". innodb_backup_batch_wait(): Look up any pages that we are about to back up. For any dirty pages, invoke buf_page_t::write_fix_try() to try to set a fake "write fix" lock-free. If the page is currently write-fixed between buf_page_t::flush() and buf_page_t::write_complete(), acquire and release a page U-latch to wait for the conflicting write to complete. InnoDB_backup::backup_batch_start(), InnoDB_backup::backup_batch_stop(): Adjust fil_space_t::backup_end and fake "write fix" of dirty pages to protect the copying of a range of pages from the underlying file. InnoDB_backup::commit(): Enqueue the remaining log to be copied. InnoDB_backup::checkpoint_complete(): If backup is running and commit() has not been called, add each completed innodb_archive_log=ON file to the queue. Else, skip or delete, as appropriate. log_t::backup_start(): If we were running with innodb_log_archive=ON, ensure that the latest file is a valid recovery starting point. That is, wait for the latest log checkpoint to be within the file. buf_flush_list_space(): Check for concurrent backup before writing each page. This is inefficient, but this function may be invoked from multiple threads concurrently, and it cannot be changed easily, especially for fil_crypt_thread(). fil_ibd_create(): Set fil_space_t::create_lsn after the file has been created. dict_load_tablespaces(): Determine the size of each file if upgrade==true. Backup depends on that. buf_dblwr_t::begin(), buf_dblwr_t::end(), buf_dblwr_t::size(): Accessors to allow BACKUP SERVER to skip the contents of the doublewrite buffer in the system tablespace. It is only useful for crash recovery in case a data page had been incompletely written by the time the server was killed. If the server is killed during a backup, the backup will be incomplete and unusable anyway. Furthermore, the page range locking makes page writes and backup mutually exclusive.