Class: Snapsync::SnapshotTransfer

Inherits:
Object
  • Object
show all
Defined in:
lib/snapsync/snapshot_transfer.rb

Overview

Snapshot transfer between two btrfs filesystems

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(config, target) ⇒ SnapshotTransfer

Returns a new instance of SnapshotTransfer.



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# File 'lib/snapsync/snapshot_transfer.rb', line 19

def initialize(config, target)
    @config, @target = config, target

    @btrfs_src = Btrfs.get(config.subvolume)
    @btrfs_dest = Btrfs.get(@target.dir)
end

Instance Attribute Details

#btrfs_dest ⇒ Btrfs (readonly)

Returns dest filesystem.

Returns:

  • (Btrfs) —

    dest filesystem



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# File 'lib/snapsync/snapshot_transfer.rb', line 17

def btrfs_dest
  @btrfs_dest
end

#btrfs_src ⇒ Btrfs (readonly)

Returns src filesystem.

Returns:

  • (Btrfs) —

    src filesystem



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# File 'lib/snapsync/snapshot_transfer.rb', line 14

def btrfs_src
  @btrfs_src
end

#config ⇒ SnapperConfig (readonly)

The snapper configuration we should synchronize

Returns:



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# File 'lib/snapsync/snapshot_transfer.rb', line 7

def config
  @config
end

#target ⇒ SyncTarget (readonly)

The target directory into which to synchronize

Returns:



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# File 'lib/snapsync/snapshot_transfer.rb', line 11

def target
  @target
end

Instance Method Details

#copy_snapshot(target_snapshot_dir, src, parent: nil) ⇒ Object

Parameters:



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# File 'lib/snapsync/snapshot_transfer.rb', line 106

def copy_snapshot(target_snapshot_dir, src, parent: nil)
    # This variable is used in the 'ensure' block. Make sure it is
    # initialized properly
    success = false

    (target_snapshot_dir + "info.xml").open('w') do |io|
        io.write (src.snapshot_dir + "info.xml").read
    end

    if parent
        parent_opt = ['-p', parent.subvolume_dir.to_s]
        estimated_size = src.size_diff_from(parent)
    else
        parent_opt = []
        estimated_size = src.size
    end

    Snapsync.info "Estimating transfer for #{src.snapshot_dir} to be #{human_readable_size(estimated_size)}"

    start = Time.now
    bytes_transferred = nil
    bytes_transferred =
        btrfs_src.popen('send', *parent_opt, src.subvolume_dir.to_s) do |send_io|
            btrfs_dest.popen('receive', target_snapshot_dir.path_part, mode: 'w', out: '/dev/null') do |receive_io|
                receive_io.sync = true
                copy_stream(send_io, receive_io, estimated_size: estimated_size)
            end
        end

    Snapsync.info "Flushing data to disk"
    btrfs_dest.run("filesystem", "sync", target_snapshot_dir.path_part)
    duration = Time.now - start
    rate = bytes_transferred / duration
    Snapsync.info "Transferred #{human_readable_size(bytes_transferred)} in #{human_readable_time(duration)} (#{human_readable_size(rate)}/s)"
    Snapsync.info "Successfully synchronized #{src.snapshot_dir}"
    true

rescue Exception => e
    subvolume_dir = target_snapshot_dir + "snapshot"
    Snapsync.warn "Failed to synchronize #{src.snapshot_dir}, deleting target directory #{subvolume_dir}"
    if subvolume_dir.directory?
        btrfs_dest.run("subvolume", "delete", subvolume_dir.path_part)
    end
    if target_snapshot_dir.directory?
        target_snapshot_dir.rmtree
    end

    raise
end

#copy_stream(send_io, receive_io, chunk_length: (1 << 20), estimated_size: 0) ⇒ Object 



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# File 'lib/snapsync/snapshot_transfer.rb', line 45

def copy_stream(send_io, receive_io, chunk_length: (1 << 20), estimated_size: 0)
    longest_message_length = 0
    counter = 0
    start = Time.now
    while !send_io.eof?
        if buffer = send_io.read(chunk_length) # 1MB buffer
            receive_io.write(buffer)

            counter += buffer.size
            rate = counter / (Time.now - start)
            remaining =
                if estimated_size > counter
                    human_readable_time((estimated_size - counter) / rate)
                elsif counter - estimated_size < 100 * 1024**2
                    human_readable_time(0)
                else
                    '?'
                end

            msg = "#{human_readable_size(counter)} (#{human_readable_size(rate)}/s), #{remaining} remaining"
            longest_message_length = [longest_message_length, msg.length].max
            print "\r%-#{longest_message_length}s" % [msg]
        end
    end
    print "\r#{" " * longest_message_length}\r"
    counter
end

#create_synchronization_point ⇒ Object 



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# File 'lib/snapsync/snapshot_transfer.rb', line 26

def create_synchronization_point
    config.create(
        description: "synchronization snapshot for snapsync",
        user_data: Hash['important' => 'yes', 'snapsync-description' => target.description, 'snapsync' => target.uuid])
end

#remove_synchronization_points(except_last: true) ⇒ Object 



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# File 'lib/snapsync/snapshot_transfer.rb', line 32

def remove_synchronization_points(except_last: true)
    synchronization_points = config.each_snapshot.find_all do |snapshot|
        snapshot.synchronization_point_for?(target)
    end
    if except_last
        synchronization_points = synchronization_points.sort_by(&:num)
        synchronization_points.pop
    end
    synchronization_points.each do |snapshot|
        config.delete(snapshot)
    end
end

#sync ⇒ Object 



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# File 'lib/snapsync/snapshot_transfer.rb', line 156

def sync
    STDOUT.sync = true

    # Do a snapper cleanup before syncing
    config.cleanup

    # First, create a snapshot and protect it against cleanup, to use as
    # synchronization point
    #
    # We remove old synchronization points on successful synchronization
    source_snapshots = config.each_snapshot.sort_by(&:num)
    sync_snapshot = source_snapshots.reverse.find do |snapshot|
        if snapshot.synchronization_point_for?(target)
            true
        elsif !snapshot.synchronization_point?
            break
        end
    end
    sync_snapshot ||= create_synchronization_point

    target_snapshots = target.each_snapshot.sort_by(&:num)
    nums_on_target = target_snapshots.map(&:num).to_set

    last_common_snapshot = source_snapshots.find do |s|
        nums_on_target.include?(s.num)
    end
    if !last_common_snapshot
        Snapsync.warn "no common snapshot found, will have to synchronize the first snapshot fully"
    end

    # Merge source and target snapshots to find out which are needed on
    # the target, and then remove the ones that are already present.
    all_snapshots = source_snapshots.find_all { |s| !nums_on_target.include?(s.num) } +
        target_snapshots
    nums_required = target.sync_policy.filter_snapshots(all_snapshots).
        map(&:num).to_set
    source_snapshots.each do |src|
        if !nums_required.include?(src.num)
            if nums_on_target.include?(src.num)
                last_common_snapshot = src
            end
            next
        elsif synchronize_snapshot(target.dir + src.num.to_s, src, parent: last_common_snapshot)
            last_common_snapshot = src
        end
    end

    if synchronize_snapshot(target.dir + sync_snapshot.num.to_s, sync_snapshot, parent: last_common_snapshot)
        Snapsync.debug "successfully copied last synchronization point #{sync_snapshot.num}, removing old ones"
        remove_synchronization_points
    end

    last_common_snapshot
end

#synchronize_snapshot(target_snapshot_dir, src, parent: nil) ⇒ Object

Parameters:



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# File 'lib/snapsync/snapshot_transfer.rb', line 74

def synchronize_snapshot(target_snapshot_dir, src, parent: nil)
    partial_marker_path = Snapshot.partial_marker_path(target_snapshot_dir)

    # Verify first if the snapshot is already present and/or partially
    # synchronized
    begin
        snapshot = Snapshot.new(target_snapshot_dir)
        if snapshot.partial?
            Snapsync.warn "target snapshot directory #{target_snapshot_dir} looks like an aborted snapsync synchronization, I will attempt to refresh it"
        else
            return true
        end
    rescue InvalidSnapshot
        if target_snapshot_dir.exist?
            Snapsync.warn "target snapshot directory #{target_snapshot_dir} already exists, but does not seem to be a valid snapper snapshot. I will attempt to refresh it"
        else
            target_snapshot_dir.mkdir
        end
        partial_marker_path.touch
    end

    if copy_snapshot(target_snapshot_dir, src, parent: parent)
        partial_marker_path.unlink
        btrfs_dest.run("filesystem", "sync", target_snapshot_dir.path_part)
        Snapsync.info "Successfully synchronized #{src.snapshot_dir}"
        true
    end
end