class Hiera::Filecache

Public Class Methods

new() click to toggle source
# File lib/hiera/filecache.rb, line 3
def initialize
  @cache = {}
end

Public Instance Methods

read(path, expected_type = Object, default=nil, &block) click to toggle source

Reads a file, optionally parse it in some way check the output type and set a default

Simply invoking it this way will return the file contents

data = read("/some/file")

But as most cases of file reading in hiera involves some kind of parsing through a serializer there's some help for those cases:

data = read("/some/file", Hash, {}) do |data|
   JSON.parse(data)
end

In this case it will read the file, parse it using JSON then check that the end result is a Hash, if it's not a hash or if reading/parsing fails it will return {} instead

Prior to calling this method you should be sure the file exist

# File lib/hiera/filecache.rb, line 27
def read(path, expected_type = Object, default=nil, &block)
  read_file(path, expected_type, &block)
rescue TypeError => detail
  Hiera.debug("#{detail.message}, setting defaults")
  @cache[path][:data] = default
rescue => detail
  error = "Reading data from #{path} failed: #{detail.class}: #{detail}"
  if default.nil?
    raise detail
  else
    Hiera.debug(error)
    @cache[path][:data] = default
  end
end
read_file(path, expected_type = Object) { |data| ... } click to toggle source

Read a file when it changes. If a file is re-read and has not changed since the last time then the last, processed, contents will be returned.

The processed data can also be checked against an expected type. If the type does not match a TypeError is raised.

No error handling is done inside this method. Any failed reads or errors in processing will be propagated to the caller

# File lib/hiera/filecache.rb, line 50
def read_file(path, expected_type = Object)
  if stale?(path)
    data = File.read(path)
    @cache[path][:data] = block_given? ? yield(data) : data

    if !@cache[path][:data].is_a?(expected_type)
      raise TypeError, "Data retrieved from #{path} is #{@cache[path][:data].class} not #{expected_type}"
    end
  end

  @cache[path][:data]
end

Private Instance Methods

path_metadata(path) click to toggle source

This is based on the old caching in the YAML backend and has a resolution of 1 second, changes made within the same second of a previous read will be ignored

# File lib/hiera/filecache.rb, line 81
def path_metadata(path)
  stat = File.stat(path)
  {:inode => stat.ino, :mtime => stat.mtime, :size => stat.size}
end
stale?(path) click to toggle source
# File lib/hiera/filecache.rb, line 65
def stale?(path)
  meta = path_metadata(path)

  @cache[path] ||= {:data => nil, :meta => nil}

  if @cache[path][:meta] == meta
    return false
  else
    @cache[path][:meta] = meta
    return true
  end
end