Class: Hiera::Filecache

Inherits:
Object
  • Object
show all
Defined in:
lib/hiera/filecache.rb

Instance Method Summary collapse

Constructor Details

#initialize ⇒ Filecache

Returns a new instance of Filecache.


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# File 'lib/hiera/filecache.rb', line 3

def initialize
  @cache = {}
end

Instance Method Details

#read(path, expected_type = Object, default = nil, &block) ⇒ Object

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


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# 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) ⇒ Object

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


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# File 'lib/hiera/filecache.rb', line 50

def read_file(path, expected_type = Object)
  if stale?(path)
    data = File.read(path, :encoding => 'BOM|UTF-8')
    @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