Class: FileWatch::SincedbValue

Inherits:
Object
  • Object
show all
Defined in:
lib/filewatch/sincedb_value.rb

Overview

Tracks the position and expiry of the offset of a file-of-interest NOTE: the ‘watched_file.bytes_read` and this `sincedb_value.position` can diverge At any given moment IF the `watched_file.bytes_read` is greater than `sincedb_value.position` then it is larger to account for bytes held in the `watched_file.buffer` in Tail mode if we quit the buffer is not flushed and we restart from the `sincedb_value.position` (end of the last line read). in Read mode the buffer is flushed as a line and both values should be the same.

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(position, last_changed_at = nil, watched_file = nil) ⇒ SincedbValue

Returns a new instance of SincedbValue.

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# File 'lib/filewatch/sincedb_value.rb', line 14

def initialize(position, last_changed_at = nil, watched_file = nil)
  @position = position # this is the value read from disk
  @last_changed_at = last_changed_at
  @watched_file = watched_file
  touch if @last_changed_at.nil? || @last_changed_at.zero?
end

Instance Attribute Details

#last_changed_at ⇒ Object (readonly)

Returns the value of attribute last_changed_at.


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# File 'lib/filewatch/sincedb_value.rb', line 12

def last_changed_at
  @last_changed_at
end

#path_in_sincedb ⇒ Object (readonly)

Returns the value of attribute path_in_sincedb.


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# File 'lib/filewatch/sincedb_value.rb', line 12

def path_in_sincedb
  @path_in_sincedb
end

#position ⇒ Object (readonly)

Returns the value of attribute position.


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# File 'lib/filewatch/sincedb_value.rb', line 12

def position
  @position
end

#watched_file ⇒ Object (readonly)

Returns the value of attribute watched_file.


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# File 'lib/filewatch/sincedb_value.rb', line 12

def watched_file
  @watched_file
end

Instance Method Details

#add_path_in_sincedb(path) ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 21

def add_path_in_sincedb(path)
  @path_in_sincedb = path # can be nil
  self
end

#clear_watched_file ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 65

def clear_watched_file
  @watched_file = nil
end

#increment_position(pos) ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 37

def increment_position(pos)
  # called when actual lines are sent to the observer listener
  # this gets serialized as its a more true indication of position than
  # chunk read size
  touch
  @position += pos
end

#last_changed_at_expires(duration) ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 26

def last_changed_at_expires(duration)
  @last_changed_at + duration
end

#reading_completed ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 69

def reading_completed
  touch
  @path_in_sincedb = @watched_file.path
  @position = @watched_file.bytes_read
end

#set_watched_file(watched_file) ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 45

def set_watched_file(watched_file)
  touch
  @watched_file = watched_file
end

#to_s ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 54

def to_s
  # consider serializing the watched_file state as well
  "#{position} #{last_changed_at}".tap do |s|
    if @watched_file.nil?
      s.concat(" ").concat(@path_in_sincedb) unless @path_in_sincedb.nil?
    else
      s.concat(" ").concat(@watched_file.path)
    end
  end
end

#touch ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 50

def touch
  @last_changed_at = Time.now.to_f
end

#unset_watched_file ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 75

def unset_watched_file
  # called in read mode only because we flushed any remaining bytes as a final line.
  # cache the position
  # we don't cache the path here because we know we are done with this file.
  # either due via the `delete` handling
  # or when read mode is done with a file.
  # in the case of `delete` if the file was renamed then @watched_file is the
  # watched_file of the previous path and the new path will be discovered and
  # it should have the same inode as before.
  # The key from the new watched_file should then locate this entry and we
  # can resume from the cached position
  return if @watched_file.nil?
  wf = @watched_file
  @watched_file = nil
  @position = wf.bytes_read
end

#update_position(pos) ⇒ Object

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# File 'lib/filewatch/sincedb_value.rb', line 30

def update_position(pos)
  # called when we reset the position to bof or eof on shrink or file read complete
  touch
  @position = pos
  @watched_file.update_bytes_read(pos) unless @watched_file.nil?
end