Class: OFlow::Actors::Persister

Inherits:
OFlow::Actor show all
Defined in:
lib/oflow/actors/persister.rb

Overview

Actor that persists records to the local file system as JSON representations of the records. Records can be the whole contents of the box received or a sub element of the contents. The key to the records are keys provided either in the record data or outside the data but somewhere else in the box received. Options for maintaining historic records and sequence number locking are included. If no sequence number is provide the Persister will assume there is no checking required and write anyway.

Records are stored as JSON with the filename as the key and sequence number. The format of the file name is <key>~<seq>.json. As an example, a record stored with a key of ‘first’ and a sequence number of 3 (third time saved) would be ‘first~3.json.

Defined Under Namespace

Classes: ExistsError, KeyError, NotFoundError, SeqError

Instance Attribute Summary collapse

Attributes inherited from OFlow::Actor

#task

Instance Method Summary collapse

Methods inherited from OFlow::Actor

#inputs, #options, #outputs, #with_own_thread

Constructor Details

#initialize(task, options) ⇒ Persister

Initializes the persister with options of:

Parameters:

  • options (Hash) —

    with keys of

    • :dir [String] directory to store the persisted records

    • :key_data [String] path to record data (default: nil (all))

    • :key_path [String] path to key for the record (default: ‘key’)

    • :seq_path [String] path to sequence for the record (default: ‘seq’)

    • :cache [Boolean] if true, cache records in memory

    • :historic [Boolean] if true, do not delete previous versions



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# File 'lib/oflow/actors/persister.rb', line 34

def initialize(task, options)
  super
  @dir = options[:dir]
  if @dir.nil?
    @dir = File.join('db', task.full_name.gsub(':', '/'))
  end
  @key_path = options.fetch(:key_path, 'key')
  @seq_path = options.fetch(:seq_path, 'seq')
  @data_path = options.fetch(:data_path, nil) # nil means all contents
  if options.fetch(:cache, true)
    # key is record key, value is [seq, rec]
    @cache = {}
  else
    @cache = nil
  end
  @historic = options.fetch(:historic, false)

  if Dir.exist?(@dir)
    unless @cache.nil?
      Dir.glob(File.join('**', '*.json')).each do |path|
        path = File.join(@dir, path)
        if File.symlink?(path)
          rec = load(path)
          unless @cache.nil?
            key, seq = key_seq_from_path(path)
            @cache[key] = [seq, rec]
          end
        end
      end
    end
  else
    `mkdir -p #{@dir}`
  end
end

Instance Attribute Details

#data_path ⇒ Object (readonly)

Returns the value of attribute data_path.



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# File 'lib/oflow/actors/persister.rb', line 23

def data_path
  @data_path
end

#dir ⇒ Object (readonly)

Returns the value of attribute dir.



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# File 'lib/oflow/actors/persister.rb', line 20

def dir
  @dir
end

#historic ⇒ Object (readonly)

Returns the value of attribute historic.



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# File 'lib/oflow/actors/persister.rb', line 24

def historic
  @historic
end

#key_path ⇒ Object (readonly)

Returns the value of attribute key_path.



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# File 'lib/oflow/actors/persister.rb', line 21

def key_path
  @key_path
end

#seq_path ⇒ Object (readonly)

Returns the value of attribute seq_path.



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# File 'lib/oflow/actors/persister.rb', line 22

def seq_path
  @seq_path
end

Instance Method Details

#caching? ⇒ Boolean

Returns true if the actor is caching records.

Returns:

  • (Boolean) 


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# File 'lib/oflow/actors/persister.rb', line 101

def caching?()
  !@cache.nil?
end

#clear(box) ⇒ Object 



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# File 'lib/oflow/actors/persister.rb', line 197

def clear(box)
  @cache = {} unless @cache.nil?
  `rm -rf #{@dir}`
  # remake the dir in preparation for future inserts
  `mkdir -p #{@dir}`
  nil
end

#delete(box) ⇒ Object 



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# File 'lib/oflow/actors/persister.rb', line 154

def delete(box)
  key = box.get(@key_path)
  @cache.delete(key) unless @cache.nil?
  linkpath = File.join(@dir, "#{key}.json")
  File.delete(linkpath)
  delete_historic(key, nil) unless @historic
  nil
end

#delete_historic(key, seq) ⇒ Object 



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# File 'lib/oflow/actors/persister.rb', line 226

def delete_historic(key, seq)
  Dir.glob(File.join(@dir, '**', "#{key}~*.json")).each do |path|
    _, s = key_seq_from_path(path)
    next if s == seq
    File.delete(path)
  end
end

#insert(box) ⇒ Object

Raises:



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# File 'lib/oflow/actors/persister.rb', line 91

def insert(box)
  key = box.get(@key_path)
  raise KeyError.new(:insert) if key.nil?
  box = box.set(@seq_path, 1)
  rec = box.get(@data_path)
  @cache[key] = [1, rec] unless @cache.nil?
  save(rec, key, 1)
end

#key_seq_from_path(path) ⇒ Object 



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# File 'lib/oflow/actors/persister.rb', line 234

def key_seq_from_path(path)
  path = File.readlink(path) if File.symlink?(path)
  base = File.basename(path)[0..-6] # strip off '.json'
  a = base.split('~')
  [a[0..-2].join('~'), a[-1].to_i]
end

#load(path) ⇒ Object 



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# File 'lib/oflow/actors/persister.rb', line 221

def load(path)
  return nil unless File.exist?(path)
  Oj.load_file(path, :mode => :object)
end

#perform(op, box) ⇒ Object 



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# File 'lib/oflow/actors/persister.rb', line 69

def perform(op, box)
  dest = box.contents[:dest]
  result = nil
  case op
  when :insert, :create
    result = insert(box)
  when :get, :read
    result = read(box)
  when :update
    result = update(box)
  when :delete, :remove
    result = delete(box)
  when :query
    result = query(box)
  when :clear
    result = clear(box)
  else
    raise OpError.new(task.full_name, op)
  end
  task.ship(dest, Box.new(result, box.tracker))
end

#query(box) ⇒ Object 



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# File 'lib/oflow/actors/persister.rb', line 163

def query(box)
  recs = {}
  expr = box.get('expr')
  if expr.nil?
    if @cache.nil?
      Dir.glob(File.join(@dir, '**/*.json')).each do |path|
        recs[File.basename(path)[0..-6]] = load(path) if File.symlink?(path)
      end
    else
      @cache.each do |key,seq_rec|
        recs[key] = seq_rec[1]
      end
    end
  elsif expr.is_a?(Proc)
    if @cache.nil?
      Dir.glob(File.join(@dir, '**/*.json')).each do |path|
        next unless File.symlink?(path)
        rec = load(path)
        key, seq = key_seq_from_path(path)
        recs[key] = rec if expr.call(rec, key, seq)
      end
    else
      @cache.each do |key,seq_rec|
        rec = seq_rec[1]
        recs[key] = rec if expr.call(rec, key, seq_rec[0])
      end
    end
  else
    # TBD add support for string safe expressions in the future
    raise Exception.new("expr can only be a Proc, not a #{expr.class}")
  end
  recs
end

#read(box) ⇒ Object 



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# File 'lib/oflow/actors/persister.rb', line 105

def read(box)
  # Should be a Hash.
  key = box.contents[:key]
  raise KeyError(:read) if key.nil?
  if @cache.nil?
    linkpath = File.join(@dir, "#{key}.json")
    rec = load(linkpath)
  else
    unless (seq_rec = @cache[key]).nil?
      rec = seq_rec[1]
    end
  end
  # If not found rec will be nil, that is okay.
  rec
end

#save(rec, key, seq) ⇒ Object

internal use only

Raises:



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# File 'lib/oflow/actors/persister.rb', line 206

def save(rec, key, seq)
  filename = "#{key}~#{seq}.json"
  path = File.join(@dir, filename)
  linkpath = File.join(@dir, "#{key}.json")
  raise ExistsError.new(key, seq) if File.exist?(path)
  Oj.to_file(path, rec, :mode => :object)
  begin
    File.delete(linkpath)
  rescue Exception
    # ignore
  end
  File.symlink(filename, linkpath)
  rec
end

#update(box) ⇒ Object

Raises:



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# File 'lib/oflow/actors/persister.rb', line 121

def update(box)
  key = box.get(@key_path)
  raise KeyError.new(:update) if key.nil?
  seq = box.get(@seq_path)
  if @cache.nil?
    if (seq_rec = @cache[key]).nil?
      raise NotFoundError.new(key)
    end
    seq = seq_rec[0] if seq.nil?
  else
    seq = 0
    has_rec = false
    Dir.glob(File.join(@dir, '**', "#{key}*.json")).each do |path|
      if File.symlink?(path)
        has_rec = true
        next
      end
      _, s = key_seq_from_path(path)
      seq = s if seq < s
    end
  end
  raise NotFoundError.new(key) unless has_rec
  raise SeqError.new(:update, key) if seq.nil? || 0 == seq

  seq += 1
  box = box.set(@seq_path, seq)
  rec = box.get(@data_path)
  @cache[key] = [seq, rec] unless @cache.nil?
  rec = save(rec, key, seq)
  delete_historic(key, seq) unless @historic
  rec
end