Class: Snapsync::Snapshot

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

Overview

Representation of a single Snapper snapshot

Defined Under Namespace

Classes: SnapshotCompareError

Constant Summary collapse

PARTIAL_MARKER = 
"snapsync-partial"

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(snapshot_dir) ⇒ Snapshot

Returns a new instance of Snapshot.

Parameters:



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# File 'lib/snapsync/snapshot.rb', line 77

def initialize(snapshot_dir)
    @snapshot_dir = snapshot_dir
    @btrfs = Btrfs.get(snapshot_dir)

    if !snapshot_dir.directory?
        raise InvalidSnapshot, "#{snapshot_dir} does not exist"
    elsif !subvolume_dir.directory?
        raise InvalidSnapshot, "#{snapshot_dir}'s subvolume directory does not exist (#{subvolume_dir})"
    end

    # This loads the information and also validates that snapshot_dir is
    # indeed a snapper snapshot
    load_info
end

Instance Attribute Details

#btrfs ⇒ Btrfs (readonly)

Returns:



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# File 'lib/snapsync/snapshot.rb', line 13

def btrfs
  @btrfs
end

#date ⇒ DateTime (readonly)

The snapshot’s date

Returns:

  • (DateTime) 


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# File 'lib/snapsync/snapshot.rb', line 30

def date
  @date
end

#num ⇒ Object (readonly)

The snapshot number



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# File 'lib/snapsync/snapshot.rb', line 33

def num
  @num
end

#snapshot_dir ⇒ Pathname (readonly)

The path to the snapshot directory

Returns:



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# File 'lib/snapsync/snapshot.rb', line 10

def snapshot_dir
  @snapshot_dir
end

#user_data ⇒ Hash<String,String> (readonly)

The snapshot’s user data

Returns:

  • (Hash<String,String>) 


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# File 'lib/snapsync/snapshot.rb', line 38

def user_data
  @user_data
end

Class Method Details

.each(snapshot_dir, with_partial: false) {|snapshot| ... } ⇒ Object

Enumerate the snapshots from the given directory

The directory is supposed to be maintained in a snapper-compatible foramt, meaning that the snapshot directory name must be the snapshot’s number

Yield Parameters:



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# File 'lib/snapsync/snapshot.rb', line 162

def self.each(snapshot_dir, with_partial: false)
    return enum_for(__method__, snapshot_dir, with_partial: with_partial) if !block_given?
    each_snapshot_raw(snapshot_dir) do |path, snapshot, error|
        if error
            Snapsync.warn "ignored #{path} in #{self}: #{error}"
        elsif snapshot.num != Integer(path.basename.to_s)
            Snapsync.warn "ignored #{path} in #{self}: the snapshot reports num=#{snapshot.num} but its directory is called #{path.basename}"
        elsif !with_partial && snapshot.partial?
            Snapsync.warn "ignored #{path} in #{self}: this is a partial snapshot"
        else
            yield snapshot
        end
    end
end

.each_snapshot_raw(snapshot_dir) {|path, snapshot, err| ... } ⇒ Object

Yield Parameters:



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# File 'lib/snapsync/snapshot.rb', line 142

def self.each_snapshot_raw(snapshot_dir)
    return enum_for(__method__, snapshot_dir) if !block_given?
    snapshot_dir.each_child do |path|
        if path.directory? && path.basename.to_s =~ /^\d+$/
            begin
                snapshot = Snapshot.new(path)
                yield(path, snapshot, nil)
            rescue InvalidSnapshot => e
                yield(path, nil, e)
            end
        end
    end
end

.partial_marker_path(snapshot_dir) ⇒ Object 



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# File 'lib/snapsync/snapshot.rb', line 42

def self.partial_marker_path(snapshot_dir)
    snapshot_dir + PARTIAL_MARKER
end

Instance Method Details

#info ⇒ SubvolumeInfo

Returns:



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# File 'lib/snapsync/snapshot.rb', line 16

def info
    # Load btrfs subvolume info
    @info = SubvolumeInfo.new(subvolume_dir) unless @info
    @info
end

#load_info ⇒ Object

Loads snapper’s info.xml, validates it and assigns the information to the relevant attributes



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# File 'lib/snapsync/snapshot.rb', line 179

def load_info
    info_xml = snapshot_dir + "info.xml"
    if !info_xml.file?
        raise InvalidSnapshot, "#{snapshot_dir}/info.xml does not exist, is this really a snapper snapshot ?"
    end

    xml = REXML::Document.new(info_xml.read)
    if !xml.root
        raise InvalidInfoFile, "#{snapshot_dir}/info.xml does not look like a snapper info file (not an XML file ?)"
    elsif xml.root.name != 'snapshot'
        raise InvalidInfoFile, "#{snapshot_dir}/info.xml does not look like a snapper info file (root is not 'snapshot')"
    end

    date = xml.root.elements.to_a('date')
    if date.empty?
        raise InvalidInfoFile, "#{snapshot_dir}/info.xml does not have a date element"
    else
        @date = DateTime.parse(date.first.text)
    end

    num = xml.root.elements.to_a('num')
    if num.empty?
        raise InvalidInfoFile, "#{snapshot_dir}/info.xml does not have a num element"
    else
        @num = Integer(num.first.text)
    end

    @user_data = Hash.new
    xml.root.elements.to_a('userdata').each do |node|
        k = node.elements['key'].text
        v = node.elements['value'].text
        user_data[k] = v
    end
end

#partial? ⇒ Boolean

Whether this snapshot has only been partially synchronized

Returns:

  • (Boolean) 


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# File 'lib/snapsync/snapshot.rb', line 55

def partial?
    partial_marker_path.exist?
end

#partial_marker_path ⇒ Pathname

A file that is used to mark the snapshot has having only been partially synchronized

Returns:



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# File 'lib/snapsync/snapshot.rb', line 50

def partial_marker_path
    self.class.partial_marker_path(snapshot_dir)
end

#size ⇒ Integer

Compute an estimate of the size of sending the whole subvolume

Returns:

  • (Integer) —

    size in bytes



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# File 'lib/snapsync/snapshot.rb', line 118

def size
    size_diff_from_gen(0)
end

#size_diff_from(snapshot) ⇒ Integer

Compute the size difference between the given snapshot and self

This is an estimate of the size required to send this snapshot using the given snapshot as parent

Parameters:

  • snapshot (Snapshot) —

    a reference snapshot, which would be used as parent in the ‘send’ operation

Returns:

  • (Integer) —

    the size in bytes of the difference between the given snapshot and the current subvolume’s state



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# File 'lib/snapsync/snapshot.rb', line 101

def size_diff_from(snapshot)
    if btrfs.mountpoint != snapshot.btrfs.mountpoint
        recv_uuid = snapshot.info.received_uuid
        local_snapshot = btrfs.subvolume_table.find do |s|
            s.uuid == recv_uuid
        end
        raise "Cannot find snapshot with uuid #{recv_uuid} locally." if local_snapshot.nil?
        snapshot_gen = local_snapshot.cgen
    else
        snapshot_gen = snapshot.info.gen_at_creation
    end
    size_diff_from_gen(snapshot_gen)
end

#size_diff_from_gen(gen) ⇒ Integer

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Compute the size of the ‘diff’ between a generation and the subvolume’s current state

Parameters:

  • gen (Integer) —

    the reference generation (the ‘from’ in the diff)

Returns:

  • (Integer) —

    size in bytes

See Also:



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# File 'lib/snapsync/snapshot.rb', line 130

def size_diff_from_gen(gen)
    btrfs.find_new(subvolume_dir, gen).inject(0) do |size, line|
        if line =~ /len (\d+)/
            size + Integer($1)
        else size
        end
    end
end

#subvolume_dir ⇒ Pathname

The path to the snapshot’s subvolume

Returns:



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# File 'lib/snapsync/snapshot.rb', line 25

def subvolume_dir; snapshot_dir + "snapshot" end

#synchronization_point? ⇒ Boolean

Whether this snapshot is one of snapsync’s synchronization points

Returns:

  • (Boolean) 


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# File 'lib/snapsync/snapshot.rb', line 65

def synchronization_point?
    user_data['snapsync']
end

#synchronization_point_for?(target) ⇒ Boolean

Whether this snapshot is one of snapsync’s synchronization points for the given target

Returns:

  • (Boolean) 


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# File 'lib/snapsync/snapshot.rb', line 71

def synchronization_point_for?(target)
    user_data['snapsync'] == target.uuid
end

#to_time ⇒ Object

This snapshot’s reference time



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# File 'lib/snapsync/snapshot.rb', line 60

def to_time
    date.to_time
end