gs_probackup

Background

gs_probackup is a tool used to manage MogDB database backup and restoration. It periodically backs up the MogDB instances so that the server can be restored when the database is faulty.

• It supports the physical backup of a standalone database or a primary node in a database.
• It supports the backup of contents in external directories, such as script files, configuration files, log files, and dump files.
• It supports incremental backup, periodic backup, and remote backup.
• It supports settings on the backup retention policy.

Prerequisites

• The MogDB database can be connected.
• To use PTRACK incremental backup, manually add enable_cbm_tracking = on to postgresql.conf.
• In order to prevent the xlog from being cleaned up before the end of the transfer, please increase the value of wal_keep_segements in the postgresql.conf file appropriately.

Important Notes

• The backup must be performed by the user who runs the database server.
• The major version number of the database server to be backed up must be the same as that of the database server to be restored.
• To back up a database in remote mode using SSH, install the database of the same major version on the local and remote hosts, and run the ssh-copy-id remote_user@remote_host command to set an SSH connection without a password between the local host backup user and the remote host database user.
• In remote mode, only the subcommands add-instance, backup, and restore can be executed.
• Before running the restore subcommand, stop the gaussdb process.
• If a user-defined tablespace exists, add the -external-dirs parameter when backing up the tablespace. Otherwise, the tablespace will not be backed up.
• If a large amount of data needs to be backed up, adjust the values of session_timeout and wal_sender_timeout in the postgresql.conf file to prevent backup timeout. In addition, adjust the value of -rw-timeout in the backup command line parameters.
• When using the -T option to redirect the external directory in the backup to a new directory during restoration, specify the -external-mapping parameter.
• After an incremental backup is restored, the created logical replication slot is unavailable and needs to be deleted and recreated.

Command Description

• Print the gs_probackup version.

  gs_probackup -V|--version
  gs_probackup version

• Display brief information about the gs_probackup command. Alternatively, display details about parameters of a specified subcommand of gs_probackup.

  gs_probackup -?|--help
  gs_probackup help [command]

• Initialize the backup directory in backup-path. The backup directory stores the contents that have been backed up. If the backup-path backup path exists, it must be empty.

  gs_probackup init -B backup-path [--help]

• Initialize a new backup instance in the backup directory of backup-path and generate the pg_probackup.conf configuration file, which saves the gs_probackupsettings of the specified data directory pgdata-path.

  gs_probackup add-instance -B backup-path -D pgdata-path --instance=instance_name
  [-E external-directories-paths]
  [remote_options]
  [--help]

• Delete the backup content related to the specified instance from the backup-path directory.

  gs_probackup del-instance -B backup-path --instance=instance_name
  [--help]

• Add the specified connection, compression, and log-related settings to the pg_probackup.conf configuration file or modify the existing settings. You are not advised to manually edit the pg_probackup.conf configuration file.

  gs_probackup set-config -B backup-path --instance=instance_name
  [-D pgdata-path] [-E external-directories-paths] [--archive-timeout=timeout]
  [--retention-redundancy=retention-redundancy] [--retention-window=retention-window] [--wal-depth=wal-depth]
  [--compress-algorithm=compress-algorithm] [--compress-level=compress-level]
  [-d dbname] [-h hostname] [-p port] [-U username]
  [logging_options] [remote_options]
  [--help]

• Add the backup-related settings to the backup.control configuration file or modify the settings.

  gs_probackup set-backup -B backup-path --instance=instance_name -i backup-id
  [--note=text] [pinning_options]
  [--help]

• Display the content of the pg_probackup.conf configuration file in the backup directory. You can specify -format=json to display the information in JSON format. By default, the plain text format is used.

  gs_probackup show-config -B backup-path --instance=instance_name
  [--format=plain|json]
  [--help]

• Display the contents of the backup directory. If instance_name and backup_id are specified, detailed information about the backup is displayed. You can specify -format=json to display the information in JSON format. By default, the plain text format is used.

  gs_probackup show -B backup-path
  [--instance=instance_name [-i backup-id]] [--archive] [--format=plain|json]
  [--help]

• Create a backup for a specified database instance.

  gs_probackup backup -B backup-path --instance=instance_name -b backup-mode
  [-D pgdata-path] [-C] [-S slot-name] [--temp-slot] [--backup-pg-log] [-j threads_num] [--progress]
  [--no-validate] [--skip-block-validation] [-E external-directories-paths] [--no-sync] [--note=text]
  [--archive-timeout=timeout] [-t rwtimeout]
  [logging_options] [retention_options] [compression_options]
  [connection_options] [remote_options] [pinning_options]
  [--help]

• Restore a specified instance from the backup copy in the backup-path directory. If an instance to be restored is specified, gs_probackup will look for its latest backup and restore it to the specified recovery objective. Otherwise, the latest backup of any instance is used.

  gs_probackup restore -B backup-path --instance=instance_name
  [-D pgdata-path] [-i backup_id] [-j threads_num] [--progress] [--force] [--no-sync] [--no-validate] [--skip-block-validation]
  [--external-mapping=OLDDIR=NEWDIR] [-T OLDDIR=NEWDIR] [--skip-external-dirs] [-I incremental_mode]
  [recovery_options] [remote_options] [logging_options]
  [--help]

• Merge all incremental backups between the specified incremental backup and its parent full backup into the parent full backup. The parent full backup will receive all merged data, while the merged incremental backup will be deleted as redundancy.

  gs_probackup merge -B backup-path --instance=instance_name -i backup_id
  [-j threads_num] [--progress] [logging_options]
  [--help]

• Delete a specified backup or delete backups that do not meet the current retention policy.

  gs_probackup delete -B backup-path --instance=instance_name
  [-i backup-id | --delete-expired | --merge-expired | --status=backup_status]
  [--delete-wal] [-j threads_num] [--progress]
  [--retention-redundancy=retention-redundancy] [--retention-window=retention-window]
  [--wal-depth=wal-depth] [--dry-run]
  [logging_options]
  [--help]

• Verify that all files required for restoring the database exist and are not damaged. If instance_nameis not specified, gs_probackupverifies all available backups in the backup directory. If instance_nameis specified and no additional options are specified, gs_probackupverifies all available backups for this backup instance. If both instance_name and backup-idor recovery objective-related options are specified, gs_probackupchecks whether these options can be used to restore the database.

  gs_probackup validate -B backup-path
  [--instance=instance_name] [-i backup-id]
  [-j threads_num] [--progress] [--skip-block-validation]
  [--recovery-target-time=time | --recovery-target-xid=xid | --recovery-target-lsn=lsn | --recovery-target-name=target-name]
  [--recovery-target-inclusive=boolean]
  [logging_options]
  [--help]

Parameter Description

Common parameters

• command

  Specifies subcommands except version and help: init, add-instance, del-instance, set-config, set-backup, show-config, show, backup, restore, merge, delete, and validate.

• -?, -help

  Displays help information about the command line parameters of gs_probackup and exits.

  Only -help can be used in subcommands; -? is forbidden.

• -V, -version

  Prints the gs_probackup version and exits.

• -B backup-path, -backup-path=backup-path

  Backup path.

  System environment variable: $BACKUP_PATH

• -D pgdata-path, -pgdata=pgdata-path

  Path of the data directory.

  System environment variable: $PGDATA

• -instance=instance_name

  Instance name.

• -i backup-id, -backup-id=backup-id

  Unique identifier of a backup.

• -format=format

  Specifies format of the backup information to be displayed. The plain and JSON formats are supported.

  Default value: plain

• -status=backup_status

  Deletes all backups in a specified state. The states are as follows:

  • OK: Backup is complete and valid.
  • DONE: Backup has been completed but not verified.
  • RUNNING: Backup is in progress.
  • MERGING: Backups are being merged.
  • DELETING: Backup is being deleted.
  • CORRUPT: Some backup files are damaged.
  • ERROR: Backup fails due to an unexpected error.
  • ORPHAN: Backup is invalid because one of its parent backups is corrupted or lost.

• -j threads_num, -threads=threads_num

  Sets the number of concurrent threads for the backup, restoration, and combination processes.

• -archive

  Displays WAL archiving information.

• -progress

  Displays progress.

• -note=text

  Adds a note to the backup.

Backup-related parameters

• -b backup-mode, -backup-mode=backup-mode

  Specifies the backup mode. The value can be FULL or PTRACK.

  FULL: creates a full backup. The full backup contains all data files.

  PTRACK: creates a PTRACK incremental backup.

• -C, -smooth-checkpoint

  Expands checkpoints within a period of time. By default, gs_probackup attempts to complete checkpoints as soon as possible.

• -S slot-name, -slot=slot-name

  Specifies the replication slot for WAL stream processing.

• -temp-slot

  Creates a temporary physical replication slot for WAL stream processing in the backup instance to ensure that all required WAL segments are still available during the backup.

  The default slot name is pg_probackup_slot, which can be changed using the -slot/-S option.

• -backup-pg-log

  Includes the log directory in the backup. This directory typically contains log messages. By default, the log directory is included, but the log file is not included. If the default log path is changed, you can use the -E parameter to back up log files. The following describes how to use the -E parameter.

• -E external-directories-paths, -external-dirs=external-directories-paths

  Includes the specified directory in the backup. This option is useful for backing up scripts in external data directories, sql dumps, and configuration files. To back up multiple external directories, use colons (:) to separate their paths in Unix.

  Example: -E /tmp/dir1:/tmp/dir2

• -skip-block-validation

  Disables block-level verification to speed up backup.

• -no-validate

  Skips the automatic verification when the backup is complete.

• -no-sync

  Disables backup file synchronization to the disk.

• -archive-timeout=timeout

  Specifies timeout interval for streaming processing, in seconds.

  Default value: 300

• -t rwtimeout

  Specifies timeout interval for a connection, in seconds.

  Default value: 120

Restoration-related parameters

• -I, -incremental-mode=none|checksum|lsn

  Reuses the valid pages available in PGDATA if they are not modified.

  Default value: none

• -external-mapping=OLDDIR=NEWDIR

  During restoration, the external directory contained in the backup is moved from OLDDIR to NEWDIR. OLDDIR and NEWDIR must be absolute paths. If the path contains an equal sign (=), use a backslash () to escape. This option can be specified for multiple directories.

• -T OLDDIR=NEWDIR, -tablespace-mapping=OLDDIR=NEWDIR

  Relocates the tablespace from the OLDDIR directory to the NEWDIR directory during the restoration. OLDDIR and NEWDIR must be absolute paths. If the path contains an equal sign (=), use a backslash () to escape. This parameter can be specified multiple times for multiple tablespaces. This parameter must be used together with -external-mapping.

• -skip-external-dirs

  Skips the external directories in the backup that are specified using the -external-dirs option. The contents of these directories will not be restored.

• -skip-block-validation

  Skips block-level verification to speed up verification. During the automatic verification before the restoration, only file-level verification is performed.

• -no-validate

  Skips the backup verification.

• -force

  Specifies the invalid state that allows ignoring backup. This flag can be used if data needs to be restored from a damaged or invalid backup. Exercise caution when using it.

Recovery objective-related parameters (recovery_options)

NOTE: Currently, continuous WAL archiving PITR cannot be configured. Therefore, parameter usage is restricted as follows: To use continuously archived WAL logs for PITR, perform the following steps: 1. Replace the target database directory with the physical backup files. 2. Delete all files in the database directory pg_xlog/. 3. Copy the archived WAL log file to the pg_xlog file. (Or you can configure restore_command in the recovery.conf file to skip this step.) 4. Create the recovery.conf file in the database directory and specify the database restoration degree. 5. Start the database. 6. Connect to the database and check whether the database is recovered to the expected status. If the expected status is reached, run the pg_xlog_replay_resume() command so that the primary node can provide services externally.

• -recovery-target-lsn=lsn

  Specifies LSN to be restored. Currently, only the backup stop LSN can be specified.

• -recovery-target-name=target-name

  Specifies named savepoint to which data is restored. You can obtain the savepoint by viewing the recovery-name column in the backup.

• -recovery-target-time=time

  Specifies time to which data is restored. Currently, only recovery-time can be specified.

• -recovery-target-xid=xid

  Specifies transaction ID to which data is restored. Currently, only recovery-xid can be specified.

• -recovery-target-inclusive=boolean

  When this parameter is set to true, the recovery objective will include the specified content.

  When this parameter is set to false, the recovery objective will not include the specified content.

  This parameter must be used together with -recovery-target-name, -recovery-target-time, -recovery-target-lsn, or -recovery-target-xid.

Retention-related parameters (retention_options)

NOTE: The following parameters can be used together with the backup and delete commands.

• -retention-redundancy=retention-redundancy

  Number of full backups retained in the data directory. The value must be a positive integer. The value 0 indicates that the setting is disabled.

  Default value: 0

• -retention-window=retention-window

  Specifies the retention period. The value must be a positive integer. The value 0 indicates that the setting is disabled.

  Default value: 0

• -wal-depth=wal-depth

  Latest number of valid backups that must be retained on each timeline to perform the PITR capability. The value must be a positive integer. The value 0 indicates that the setting is disabled.

  Default value: 0

• -delete-wal

  Deletes unnecessary WAL files from any existing backup.

• -delete-expired

  Deletes the backups that do not comply with the retention policy defined in the pg_probackup.conf configuration file.

• -merge-expired

  Merges the oldest incremental backup that meets the retention policy requirements with its expired parent backup.

• -dry-run

  Displays the status of all available backups. Expired backups will not be deleted or merged.

Fixed backup-related parameters (pinning_options)

NOTE: To exclude certain backups from the established retention policy, you can use the following parameters with the backup and set-backup commands.

• -ttl=interval

  Specifies a fixed amount of time to back up data from the restoration time. The value must be a positive integer. The value 0 indicates that the backup is canceled.

  Supported unit: ms, s, min, h, d (default value: s)

  For example, -ttl=30d.

• -expire-time=time

  Specifies the timestamp when the backup is invalid. The time stamp must comply with the ISO-8601 standard.

  For example, -expire-time='2020-01-01 00:00:00+03'.

Log-related parameters (logging_options)

Log levels: verbose, log, info, warning, error, and off.

• -log-level-console=log-level-console

  Sets the level of logs to be sent to the console. Each level contains all the levels following it. A higher level indicates fewer messages sent. If this parameter is set to off, the log recording function of the console is disabled.

  Default value: info

• -log-level-file=log-level-file

  Sets the level of logs to be sent to the log file. Each level contains all the levels following it. A higher level indicates fewer messages sent. If this parameter is set to off, the log file recording function is disabled.

  Default value: off

• -log-filename=log-filename

  Specifies the name of the log file to be created. The file name can use the strftime mode. Therefore, %-escapes can be used to specify the file name that changes with time.

  For example, if the pg_probackup-%u.log mode is specified, pg_probackup generates a log file each day of the week, with %u replaced by the corresponding decimal number, that is, pg_probackup-1.logindicates Monday.pg_probackup-2.log indicates Tuesday, and so on.

  This parameter is valid if the -log-level-file parameter is specified to enable log file recording.

  Default value: pg_probackup.log

• -error-log-filename=error-log-filename

  Specifies the name of the log file that is used only for error logs. The specifying method is the same as that of the -log-filename parameter.

  It is used for troubleshooting and monitoring.

• -log-directory=log-directory

  Specifies the directory where log files are created. The value must be an absolute path. This directory is created when the first log is written.

  Default value: $BACKUP_PATH/log

• -log-rotation-size=log-rotation-size

  Specifies the maximum size of a log file. If the maximum size is reached, the log file will be circulated after the gs_probackup command is executed. The help and version commands will not lead to a log file circulation. The value 0 indicates that the file size-based loop is disabled.

  The unit can be KB, MB, GB, or TB. The default unit is KB.

  Default value: 0

• -log-rotation-age=log-rotation-age

  Maximum life cycle of a log file. If the maximum size is reached, the log file will be circulated after the gs_probackup command is executed. The help and version commands will not lead to a log file circulation. The $BACKUP_PATH/log/log_rotation directory saves the time of the last created log file. The value 0 indicates that the time-based loop is disabled.

  Supported unit: ms, s, min, h, d (default value: min)

  Default value: 0

Connection-related parameters (connection_options)

NOTE: The following parameters can be used together with the backup command.

• -d dbname, -pgdatabase=dbname

  Specifies the name of the database to connect to. This connection is only used to manage the backup process. Therefore, you can connect to any existing database. If this parameter is not specified in the command line, the PGDATABASE environment variable, or the pg_probackup.conf configuration file, gs_probackup attempts to obtain the value from the PGUSER environment variable. If the PGUSER variable is not set, the value is obtained from the current user name.

  System environment variable: $PGDATABASE

• -h hostname, -pghost=hostname

  Specifies the host name of the system on which the server is running. If the value begins with a slash (/), it is used as the directory for the UNIX domain socket.

  System environment variable: $PGHOST

  Default value: local socket

• -p port, -pgport=port

  Specifies the TCP port or local Unix domain socket file name extension on which the server is listening for connections.

  System environment variable: $PGPORT

  Default value: 5432

• -U username, -pguser=username

  Specifies the username of the host to be connected.

  System environment variable: $PGUSER

• -w, -no-password

  Never issues a password prompt. The connection attempt fails if the host requires password verification and the password is not provided in other ways. This option is useful in batch jobs and scripts in which no user password is required.

• -W password, -password=password

  Specifies the user password for connection. If the host uses the trust authentication policy, the administrator does not need to enter the -W option. If the -W option is not provided and you are not a system administrator, the system will ask you to enter a password.

Compression-related parameters (compression_options)

NOTE: The following parameters can be used together with the backup command.

• -compress-algorithm=compress-algorithm

  Specifies the algorithm used to compress data file.

  The value can be zlib, pglz, or none. If zlib or pglz is set, compression is enabled. By default, the compression function is disabled.

  Default value: none

• -compress-level=compress-level

  Specifies the compression level. Value range: 0-9

  • 0 indicates no compression.
  • 1 indicates that the compression ratio is the lowest and processing speed the fastest.
  • 9 indicates that the compression ratio is the highest and processing speed the slowest.
  • This parameter can be used together with -compress-algorithm.

  Default value: 1

• -compress

  Compresses with -compress-algorithm=zlib and -compress-level=1.

Remote mode-related parameters (remote_options)

NOTE: The following are parameters that remotely run gs_probackup through SSH, and can be used together with the add-instance, set-config, backup, and restore commands.

• -remote-proto=protocol

  Specifies the protocol used for remote operations. Currently, only the SSH protocol is supported. Valid value:

  ssh: enables the remote backup mode through SSH. This is the default.

  none: The remote mode is disabled explicitly.

  If -remote-host is specified, this parameter can be omitted.

• -remote-host=destination

  Specifies the IP address or host name of the remote host to be connected.

• -remote-port=port

  Specifies the port number of the remote host to be connected.

  Default value: 22

• -remote-user=username

  Specifies the remote host user for SSH connection. If this parameter is not specified, the user who initiates the SSH connection is used.

  Default value: the current user.

• -remote-path=path

  Specifies the installation directory of gs_probackup in the remote system.

  Default value: current path

• -remote-lib=libpath

  Specifies the lib directory where gs_probackup is installed in the remote system.

• -ssh-options=ssh_options

  Specifies the character string of the SSH command line parameter.

  Example: -ssh-options='-c cipher_spec -F configfile'

  NOTE:

  • If the server does not respond due to a temporary network fault, gs_probackupwill exit after waiting for archive-timeout seconds (300 seconds is set by default).
  • If the LSN of the standby server is different from that of the primary server, the database continuously updates the following log information. In this case, you need to rebuild the standby server.

  LOG: walsender thread shut down
  LOG: walsender thread started
  LOG: received wal replication command: IDENTIFY_VERSION
  LOG: received wal replication command: IDENTIFY_MODE
  LOG: received wal replication command: IDENTIFY_SYSTEM
  LOG: received wal replication command: IDENTIFY_CONSISTENCE 0/D0002D8
  LOG: remote request lsn/crc: [xxxxx] local max lsn/crc: [xxxxx]

Backup Process

1. Initialize the backup directory. Create the backups/ and wal/ subdirectories in the specified directory to store backup files and WAL files respectively.

   gs_probackup init -B backup_dir

2. Add a new backup instance. gs_probackup can store backups of multiple database instances in the same backup directory.

   gs_probackup add-instance -B backup_dir -D data_dir --instance instance_name

3. Create a backup for a specified database instance. Before performing an incremental backup, you must create at least one full backup.

   gs_probackup backup -B backup_dir --instance instance_name -b backup_mode

4. Restore data from the backup of a specified instance.

   gs_probackup restore -B backup_dir --instance instance_name -D pgdata-path -i backup_id

Troubleshooting

Problem Description

Cause and Solution

ERROR: query failed: ERROR: canceling statement due to conflict with recovery

Cause: The operation performed on the standby node is accessing the storage row. The corresponding row is modified or deleted on the primary node, and the Xlog is replayed on the standby node. As a result, the operation is canceled on the standby node. Solution: 1. Increase the values of the following parameters: max_standby_archive_delay max_standby_streaming_delay 2. Add the following configuration item: hot_standby_feedback = on