Class: Snapsync::TimelineSyncPolicy

Inherits:
DefaultSyncPolicy show all
Defined in:
lib/snapsync/timeline_sync_policy.rb

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(reference: Time.now) ⇒ TimelineSyncPolicy

Returns a new instance of TimelineSyncPolicy.



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# File 'lib/snapsync/timeline_sync_policy.rb', line 8

def initialize(reference: Time.now)
    @reference = reference
    @timeline = Array.new
    @periods = Array.new
end

Instance Attribute Details

#periods ⇒ Object (readonly)

Returns the value of attribute periods.



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# File 'lib/snapsync/timeline_sync_policy.rb', line 6

def periods
  @periods
end

#reference ⇒ Object (readonly)

Returns the value of attribute reference.



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# File 'lib/snapsync/timeline_sync_policy.rb', line 3

def reference
  @reference
end

#timeline ⇒ Object (readonly)

Returns the value of attribute timeline.



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# File 'lib/snapsync/timeline_sync_policy.rb', line 4

def timeline
  @timeline
end

Class Method Details

.from_config(config) ⇒ Object 



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

def self.from_config(config)
    policy = new
    policy.parse_config(config)
    policy
end

Instance Method Details

#add(period, count) ⇒ Object

Add an element to the timeline

Examples:

keep one snapshot every day for the last 10 days

cleanup.add(:day, 10)

Parameters:

  • period (Symbol) —

    the period (:year, :month, :week, :day, :hour)

  • count (Integer) —

    how many units of this period should be kept



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# File 'lib/snapsync/timeline_sync_policy.rb', line 48

def add(period, count)
    beginning_of_day   = reference.to_date
    beginning_of_week  = beginning_of_day.prev_day(beginning_of_day.wday + 1)
    beginning_of_month = beginning_of_day.prev_day(beginning_of_day.mday - 1)
    beginning_of_year  = beginning_of_day.prev_day(beginning_of_day.yday - 1)
    beginning_of_hour  = beginning_of_day.to_time + (reference.hour * 3600)

    timeline = self.timeline.dup
    if period == :year
        count.times do
            timeline << beginning_of_year.to_time
            beginning_of_year = beginning_of_year.prev_year
        end
    elsif period == :month
        count.times do
            timeline << beginning_of_month.to_time
            beginning_of_month = beginning_of_month.prev_month
        end
    elsif period == :week
        count.times do
            timeline << beginning_of_week.to_time
            beginning_of_week = beginning_of_week.prev_day(7)
        end
    elsif period == :day
        count.times do
            timeline << beginning_of_day.to_time
            beginning_of_day = beginning_of_day.prev_day
        end
    elsif period == :hour
        count.times do |i|
            timeline << beginning_of_hour
            beginning_of_hour = beginning_of_hour - 3600
        end
    else
        raise ArgumentError, "unknown period name #{period}"
    end

    periods << [period, count]
    @timeline = timeline.sort.uniq
end

#compute_required_snapshots(target_snapshots) ⇒ Object

Given a list of snapshots, computes those that should be kept to honor the timeline constraints



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# File 'lib/snapsync/timeline_sync_policy.rb', line 91

def compute_required_snapshots(target_snapshots)
    keep_flags = Hash.new { |h,k| h[k] = [false, []] }

    target_snapshots = target_snapshots.sort_by(&:num)

    # Mark all important snapshots as kept
    target_snapshots.each do |s|
        if s.user_data['important'] == 'yes'
            keep_flags[s.num][0] = true
            keep_flags[s.num][1] << "marked as important"
        end
    end

    # For each timepoint in the timeline, find the newest snapshot that
    # is not before the timepoint
    merged_timelines = (target_snapshots.to_a + timeline).sort_by do |s|
        s.to_time
    end
    matching_snapshots = [target_snapshots.first]
    merged_timelines.each do |obj|
        if obj.kind_of?(Snapshot)
            matching_snapshots[-1] = obj
        else
            s = matching_snapshots.last
            matching_snapshots[-1] = [s, obj]
            matching_snapshots << s
        end
    end
    matching_snapshots.pop
    matching_snapshots.each do |(s, timepoint)|
        keep_flags[s.num][0] = true
        keep_flags[s.num][1] << "timeline(#{timepoint})"
    end

    # Finally, guard against race conditions. Always keep all snapshots
    # between the last-to-keep and the last
    target_snapshots.reverse.each do |s|
        break if keep_flags[s.num][0]
        keep_flags[s.num][0] = true
        keep_flags[s.num][1] << "last snapshot"
    end
    keep_flags
end

#filter_snapshots(snapshots) ⇒ Object 



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# File 'lib/snapsync/timeline_sync_policy.rb', line 135

def filter_snapshots(snapshots)
    Snapsync.debug do
        Snapsync.debug "Filtering snapshots according to timeline"
        Snapsync.debug "Snapshots: #{snapshots.map(&:num).sort.join(", ")}"
        timeline.each do |t|
            Snapsync.debug "  #{t}"
        end
        break
    end

    default_policy = DefaultSyncPolicy.new
    snapshots  = default_policy.filter_snapshots(snapshots)

    keep_flags = compute_required_snapshots(snapshots)
    snapshots.sort_by(&:num).find_all do |s|
        keep, reason = keep_flags.fetch(s.num, nil)
        if keep
            Snapsync.debug "Timeline: selected snapshot #{s.num} #{s.date.to_time}"
            reason.each do |r|
                Snapsync.debug "  #{r}"
            end
        else
            Snapsync.debug "Timeline: not selected snapshot #{s.num} #{s.date.to_time}"
        end

        keep
    end
end

#parse_config(config) ⇒ Object 



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# File 'lib/snapsync/timeline_sync_policy.rb', line 20

def parse_config(config)
    config.each_slice(2) do |period, count|
        add(period.to_sym, Integer(count))
    end
end

#pretty_print(pp) ⇒ Object 



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

def pretty_print(pp)
    pp.text "timeline policy"
    pp.nest(2) do
        pp.seplist(periods) do |pair|
            pp.breakable
            pp.text "#{pair[0]}: #{pair[1]}"
        end
    end
end

#to_config ⇒ Object 



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

def to_config
    periods.flatten
end