Synco Development

Synco is a tool for scripted synchronization and backups. It provides a custom Ruby DSL for describing backup and synchronization tasks involving one more more system and disk. It is designed to provide flexibility while reducing the complexity multi-server backups.

  • Single and multi-server data synchronization.
  • Incremental backups both locally and remotely.
  • Backup staging and coordination.
  • Backup verification using Fingerprint.
  • Data backup redundancy controlled via DNS.

Installation

Add this line to your application's Gemfile:

gem 'synco'

And then execute:

$ bundle

Or install it yourself as:

$ gem install synco

Usage

Synco imposes a particular structure regarding the organisation of backup scripts: Backup scripts involve a set of servers and directories. A server is a logical unit where files are available or stored. Directories are relative paths which are resolved relative to a server's root path.

A simple backup script might look something like this:

#!/usr/bin/env ruby

require 'synco'
require 'synco/methods/rsync'

Synco::run_script do |script|
    script.method = Synco::Methods::RSync.new(archive: true)

    server(:master) do |server|
        server.host = "server.example.com"
        server.root = "/"
    end

    server(:backup) do |server|
        server.host = "backup.example.com"
        server.root = "/tank/backups/server.example.com"
    end

    backup('etc', 'var', 'srv', 'home', 
        arguments: %W{--exclude cache/ --exclude tmp/}
    )
end

This will produce an identical copy using rsync of the specified directories. As an example server.example.com:/etc would be copied to backup.example.com:/tank/backups/server.example.com/etc.

RSync Snapshots

Building on the above backup, you can use Synco::Methods::RSyncSnapshot which supports snapshot based backups. It creates a snapshot into a sub-directory called latest.snapshot and uses RSync's --link-dest to hard-link files when unchanged. Synco provides scripts to rotate and prune these backups as required, but you must invoke them as part of the script:

server(:backup) do |server|
    server.host = "backup.example.com"
    server.root = "/"

    server.on(:success) do
        run "synco", "rotate", chdir: target_server.root
        run "synco", "prune", chdir: target_server.root
    end
end

These commands can also be run from the command line.

rotate [--format <name>] [--latest <name>] [--snapshot <name>]
    Rotate a backup snapshot into a timestamped directory.

    [--format <name>]    Set the name of the backup rotations, including strftime expansions.  Default: %Y.%m.%d-%H.%M.%S
    [--latest <name>]    The name of the latest backup symlink.                                Default: latest           
    [--snapshot <name>]  The name of the in-progress backup snapshot.                          Default: latest.snapshot  

prune [--hourly <count>] [--daily <count>] [--weekly <count>] [--monthly <count>] [--quarterly <count>] [--yearly <count>] [--format <name>] [--latest <name>] [--keep <new|old>] [--dry]
    Prune old backups to reduce disk usage according to a given policy.

    [--hourly <count>]     Set the number of hourly backups to keep.                             Default: 24               
    [--daily <count>]      Set the number of daily backups to keep.                              Default: 28               
    [--weekly <count>]     Set the number of weekly backups to keep.                             Default: 52               
    [--monthly <count>]    Set the number of monthly backups to keep.                            Default: 36               
    [--quarterly <count>]  Set the number of quaterly backups to keep.                           Default: 40               
    [--yearly <count>]     Set the number of yearly backups to keep.                             Default: 20               
    [--format <name>]      Set the name of the backup rotations, including strftime expansions.  Default: %Y.%m.%d-%H.%M.%S
    [--latest <name>]      The name of the latest backup symlink.                                Default: latest           
    [--keep <new|old>]     Keep the younger or older backups within the same period division     Default: old              
    [--dry]                Print out what would be done rather than doing it.

Mounting Disks

Synco supports mounting disks before the backup begins and unmounting them after done. The specifics of this process may require some adjustment based on your OS. For example on linux, sudo is used to invoke mount and umount.

server(:destination) do |server|
    self.mountpoint = '/mnt/backups'
    self.root = File.join(server.mountpoint, 'laptop')

    server.on(:prepare) do
        # synco mount uses labels, e.g. the disk partition has LABEL=backups
        target_server.run "synco", "mount", target_server.mountpoint, 'backups'
    end

    server.on(:finish) do
        target_server.run "synco", "unmount", target_server.mountpoint
    end
end

On Linux, you might want to create the file /etc/sudoers.d/synco with the following contents:

%wheel ALL=(root) NOPASSWD: /bin/mount
%wheel ALL=(root) NOPASSWD: /bin/umount

Please make sure you take the time to educate yourself on the security of such a setup.

Database Backups

If you'd like to dump data before running the backup, it's possible using the event handling mechanisms:

server(:master) do |server|
    server.host = "server.example.com"
    server.root = "/"

    server.on(:prepare) do
        # Dump MySQL to /srv/mysql
        run '/etc/lsync/mysql-backup.sh'
    end
end

The exact contents of mysql-backup.sh will depend on your requirements, but here is an example:

#!/usr/bin/env bash

BACKUP_DIR=/srv/mysql
MYSQL=/usr/bin/mysql
MYSQLDUMP=/usr/bin/mysqldump

databases=`mysql --user=backup -e "SHOW DATABASES;" | grep -Ev "(Database|information_schema|performance_schema|_test|_restore)"`

# http://stackoverflow.com/questions/451404/how-to-obtain-a-correct-dump-using-mysqldump-and-single-transaction-when-ddl-is
MYSQLDUMP_OPTIONS="--force --skip-opt --single-transaction --add-drop-table --create-options --quick --extended-insert --set-charset --disable-keys"

for db in $databases; do
    echo "Dumping database $db to $BACKUP_DIR/$db.sql.xz..."
    mysqldump --user=backup $MYSQLDUMP_OPTIONS --databases $db | xz > "$BACKUP_DIR/$db.sql.xz"
done

Fingerprint Integration

It is possible to make a cryptographic checksum of the data. On a filesystem that support immutable snapshots, you can do this before the data is copied. For traditional filesystems, you generally need to do this afterwards.

server(:master) do |server|
    server.host = "server.example.com"
    server.root = "/"

    server.on(:success) do
        # Run fingerprint on the backup data:
        run 'fingerprint', '--root', target_server.root, 'analyze'
    end
end

Fingerprint is used in many of the specs to verify file copies.

ZFS Snapshots

This part of Synco is still under heavy development

Synco can manage synchronization and backups of ZFS partitions. However, to use the standard tools, it is necessary to enable zfs_admin_snapshot, in /etc/modprobe.d/zfs.conf:

options zfs zfs_admin_snapshot=1

Propagate user permissions for the ZFS partition:

sudo zfs allow -ld -u `whoami` create,mount,send,receive,snapshot tank/test

Backup staging

Synco in a previous life supported backup staging. However, at this time it's not available except in a very limited form: backup scripts which use Synco.run_script use explicit locking so that it's not possible to run the same backup at the same time. In the future, staging sequential and parallel backups will be added.

DNS Failover

This behaviour is not well tested

Synco uses DNS to resolve the master server. This allows for bi-directional synchronization and other interesting setups.

Firstly, a backup script defaults to the server with the name :master as the master, where data is replicated FROM.

However, it is possible instead to specify a hostname, e.g. primary.example.com. Then, specify several servers, e.g. s01.example.com, s02.example.com and so on:

Synco::run_script do |script|
    script.method = Synco::Methods::RSync.new(archive: true)

    script.master = "primary.example.com"

    server("s01.example.com") do |server|
        server.root = "/"
    end

    server("s02.example.com") do |server|
        server.root = "/"
    end

    backup('srv/http', 
        arguments: %W{--exclude cache/ --exclude tmp/}
    )
end

When you run the script, the behaviour will depend on whether primary.example.com points to s01.example.com or s02.example.com. The data will always be copied from the master server to the other servers.

Contributing

  1. Fork it
  2. Create your feature branch (git checkout -b my-new-feature)
  3. Commit your changes (git commit -am 'Add some feature')
  4. Push to the branch (git push origin my-new-feature)
  5. Create new Pull Request

License

Released under the MIT license.

Copyright, 2016, by Samuel G. D. Williams.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.