class Hiera::Filecache
Public Class Methods
# File lib/hiera/filecache.rb, line 3 def initialize @cache = {} end
Public Instance Methods
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 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 #{data.class} not #{expected_type}" end end @cache[path][:data] end
Private Instance Methods
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
# 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