Hiera::Backend

Public Class Methods

datadir(backend, scope) click to toggle source

Data lives in /var/lib/hiera by default. If a backend supplies a datadir in the config it will be used and subject to variable expansion based on scope

# File lib/hiera/backend.rb, line 9
def datadir(backend, scope)
  backend = backend.to_sym
  default = Hiera::Util.var_dir

  if Config.include?(backend)
    parse_string(Config[backend][:datadir] || default, scope)
  else
    parse_string(default, scope)
  end
end
datafile(backend, scope, source, extension) click to toggle source

Finds the path to a datafile based on the Backend#datadir and extension

If the file is not found nil is returned

# File lib/hiera/backend.rb, line 24
def datafile(backend, scope, source, extension)
  file = File.join([datadir(backend, scope), "#{source}.#{extension}"])

  unless File.exist?(file)
    Hiera.debug("Cannot find datafile #{file}, skipping")

    return nil
  end

  return file
end
datasources(scope, override=nil, hierarchy=nil) click to toggle source

Constructs a list of data sources to search

If you give it a specific hierarchy it will just use that else it will use the global configured one, failing that it will just look in the 'common' data source.

An override can be supplied that will be pre-pended to the hierarchy.

The source names will be subject to variable expansion based on scope

# File lib/hiera/backend.rb, line 47
def datasources(scope, override=nil, hierarchy=nil)
  if hierarchy
    hierarchy = [hierarchy]
  elsif Config.include?(:hierarchy)
    hierarchy = [Config[:hierarchy]].flatten
  else
    hierarchy = ["common"]
  end

  hierarchy.insert(0, override) if override

  hierarchy.flatten.map do |source|
    source = parse_string(source, scope)
    yield(source) unless source == "" or source =~ /(^\/|\/\/|\/$)/
  end
end
lookup(key, default, scope, order_override, resolution_type) click to toggle source

Calls out to all configured backends in the order they were specified. The first one to answer will win.

This lets you declare multiple backends, a possible use case might be in Puppet where a Puppet module declares default data using in-module data while users can override using JSON/YAML etc. By layering the backends and putting the Puppet one last you can override module author data easily.

Backend instances are cached so if you need to connect to any databases then do so in your constructor, future calls to your backend will not create new instances

# File lib/hiera/backend.rb, line 152
def lookup(key, default, scope, order_override, resolution_type)
  @backends ||= {}
  answer = nil

  Config[:backends].each do |backend|
    if constants.include?("#{backend.capitalize}_backend") || constants.include?("#{backend.capitalize}_backend".to_sym)
      @backends[backend] ||= Backend.const_get("#{backend.capitalize}_backend").new
      new_answer = @backends[backend].lookup(key, scope, order_override, resolution_type)

      if not new_answer.nil?
        case resolution_type
        when :array
          raise Exception, "Hiera type mismatch: expected Array and got #{new_answer.class}" unless new_answer.kind_of? Array or new_answer.kind_of? String
          answer ||= []
          answer << new_answer
        when :hash
          raise Exception, "Hiera type mismatch: expected Hash and got #{new_answer.class}" unless new_answer.kind_of? Hash
          answer ||= {}
          answer = new_answer.merge answer
        else
          answer = new_answer
          break
        end
      end
    end
  end

  answer = resolve_answer(answer, resolution_type) unless answer.nil?
  answer = parse_string(default, scope) if answer.nil? and default.is_a?(String)

  return default if answer.nil?
  return answer
end
parse_answer(data, scope, extra_data={}) click to toggle source

Parses a answer received from data files

Ultimately it just pass the data through parse_string but it makes some effort to handle arrays of strings as well

# File lib/hiera/backend.rb, line 106
def parse_answer(data, scope, extra_data={})
  if data.is_a?(Numeric) or data.is_a?(TrueClass) or data.is_a?(FalseClass)
    return data
  elsif data.is_a?(String)
    return parse_string(data, scope, extra_data)
  elsif data.is_a?(Hash)
    answer = {}
    data.each_pair do |key, val|
      answer[key] = parse_answer(val, scope, extra_data)
    end

    return answer
  elsif data.is_a?(Array)
    answer = []
    data.each do |item|
      answer << parse_answer(item, scope, extra_data)
    end

    return answer
  end
end
parse_string(data, scope, extra_data={}) click to toggle source

Parse a string like '%{foo}' against a supplied scope and additional scope. If either scope or extra_scope includes the varaible 'foo' it will be replaced else an empty string will be placed.

If both scope and extra_data has "foo" scope will win. See hiera-puppet for an example of this to make hiera aware of additional non scope variables

# File lib/hiera/backend.rb, line 73
def parse_string(data, scope, extra_data={})
  return nil unless data

  tdata = data.clone

  if tdata.is_a?(String)
    while tdata =~ /%\{(.+?)\}/
      begin
        var = $1

        val = ""

        # Puppet can return :undefined for unknown scope vars,
        # If it does then we still need to evaluate extra_data
        # before returning an empty string.
        if scope[var] && scope[var] != :undefined
            val = scope[var]
        elsif extra_data[var]
            val = extra_data[var]
        end
      end until val != "" || var !~ /::(.+)/

      tdata.gsub!(/%\{(::)?#{var}\}/, val)
    end
  end

  return tdata
end
resolve_answer(answer, resolution_type) click to toggle source
# File lib/hiera/backend.rb, line 128
def resolve_answer(answer, resolution_type)
  case resolution_type
  when :array
    [answer].flatten.uniq.compact
  when :hash
    answer # Hash structure should be preserved
  else
    answer
  end
end

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