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wsrep_sst_mariabackup

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wsrep_sst_mariabackup Variables

The wsrep_sst_mariabackup script handles the actual data transfer and processing during an SST. The variables it reads from the [sst] group control aspects of the backup format, compression, transfer mechanism, and logging.

The wsrep_sst_mariadbbackup script parses the following options:

  • sfmt (streamfmt)

    • Default: mbstream

    • Description: Defines the streaming format used by mariabackup for the SST. mbstream indicates that mariabackup will output a continuous stream of data. Other potential values (though not explicitly shown as defaults) might be related to different backup methods or tools.

  • tfmt (transferfmt)

    • Default: socat

    • Description: Specifies the transfer format or utility used to move the data stream from the donor to the joiner node. socat is a common command-line tool for data transfer, often used for setting up various network connections.

  • sockopt (socket options)

    • Description: Allows additional socket options to be passed to the underlying network communication. This includes settings for TCP buffers, keep-alives, or other network-related tunables to optimize transfer performance.

  • progress

    • Description: Controls whether progress information about the SST is displayed or logged. Enabling this option provides visual indicators or detailed log entries about the transfer's advancement.

  • ttime (time)

    • Default: 0

    • Description: A timeout value in seconds for certain operations during the SST, or a flag related to timing the transfer. A value of 0 indicates no timeout or that timing is handled elsewhere.

  • cpat

    • Description: Related to a "copy pattern" or specific path handling during the SST. Its function depends on how the wsrep_sst_mariabackup script uses this pattern for file or directory management.

  • scomp (compressor)

    • Description: Specifies the compression utility to be used on the data stream before transfer. Common values include gzip, pigz, lz4, or qpress, which reduce the data size for faster transmission over the network.

  • sdecomp (decompressor)

    • Description: Specifies the decompression utility to be used on the receiving end (joiner node) to decompress the data stream that was compressed by scomp. It should correspond to the scomp setting.

  • rlimit (resource limit)

    • Description: Sets a maximum data transfer rate for State Snapshot Transfers (SST) in which the node serves as a donor. The rlimit parameter accepts any value supported by the pv utility’s --rate-limit option. Note that using this option requires progress to be specified and the pv utility to be installed on the system.

  • uextra (use-extra)

    • Default: 0

    • Description: Controls the SST connection method that mariabackup uses to connect to the local MariaDB server. By default (uextra=0), mariabackup connects through the standard database port. When uextra=1 is enabled, the connection attempts to use either:

      • The unix socket (if available), or

      • The extra_port (if specified in MariaDB server settings).

  • speciald (sst-special-dirs)

    • Default: 1

    • Description: A boolean flag that controls whether mariabackup handles special directories (e.g., innodb_log_group_home_dir, datadir) in a specific way during the SST, rather than just copying them as regular files. This is important for maintaining data consistency.

  • stimeout (sst-initial-timeout)

    • Default: 300

    • Description: Sets an initial timeout in seconds for the SST process. If the SST doesn't make progress or complete within this initial period, it might be aborted.

  • ssyslog (sst-syslog)

    • Default: 0

    • Description: A boolean flag (0 or 1) that controls whether SST-related messages should be logged to syslog. This can be useful for centralized logging and monitoring of Galera cluster events.

  • sstlogarchive (sst-log-archive)

    • Default: 1

    • Description: A boolean flag (0 or 1) that determines whether SST logs should be archived. Archiving logs helps in post-mortem analysis and troubleshooting of SST failures.

  • sstlogarchivedir (sst-log-archive-dir)

    • Description: Specifies the directory where SST logs should be archived if sstlogarchive is enabled.

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