Class: Regentanz::Cache::File

Inherits:
Base
  • Object
show all
Defined in:
lib/regentanz/cache/file.rb

Overview

Implements file-based caching. Cache files are stored in Regentanz.configuration.cache_dir and are prefixed with Regentanz.configuration.cache_prefix.

Instance Method Summary collapse

Methods inherited from Base

lint, sanitize_key

Instance Method Details

#available?(key) ⇒ Boolean

Cache is available (n.b. not necessarily #valid?) if a file exists for key

Returns:

  • (Boolean) 


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# File 'lib/regentanz/cache/file.rb', line 12

def available?(key)
  ::File.exists?(filename(key)) rescue nil
end

#expire!(key) ⇒ Object

Unlinks the cache file for key



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# File 'lib/regentanz/cache/file.rb', line 17

def expire!(key)
  return false unless available?(key)
  begin
    ::File.delete(filename(key))
    true
  rescue
  end
end

#filename(key) ⇒ Object 



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# File 'lib/regentanz/cache/file.rb', line 26

def filename(key)
  ::File.join(Regentanz.configuration.cache_dir, "#{Regentanz.configuration.cache_prefix}_#{key}.xml")
end

#get(key) ⇒ Object

Retrieves content of #filename for key



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# File 'lib/regentanz/cache/file.rb', line 31

def get(key)
  if available?(key)
    ::File.open(filename(key), "r") { |file| file.read } rescue nil
  end
end

#set(key, value) ⇒ Object

Stores value in #filename for key



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# File 'lib/regentanz/cache/file.rb', line 38

def set(key, value)
  begin
    ::File.open(filename(key), "w") { |file| file.puts value }
    filename(key)
  rescue
  end
end

#set_retry_state! ⇒ Object

Persists the timeout state by writing a retry_marker file



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# File 'lib/regentanz/cache/file.rb', line 77

def set_retry_state!
  ::File.open(Regentanz.configuration.retry_marker, "w+").close
  waiting_for_retry?
end

#unset_retry_state! ⇒ Object

Checks if we’ve waited long enough. Deletes a possible retry marker file (and returns true) if so or returns false if not



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# File 'lib/regentanz/cache/file.rb', line 68

def unset_retry_state!
  marker = Regentanz.configuration.retry_marker
  if waiting_for_retry? and ::File.new(marker).mtime < Regentanz.configuration.retry_ttl.seconds.ago
    ::File.delete(marker) if ::File.exists?(marker)
    true
  end
end

#valid?(key) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/regentanz/cache/file.rb', line 46

def valid?(key)
  return false unless available?(key)
  begin
    # TODO delegate XML parsing and verification
    doc  = REXML::Document.new(get(key))
    node = doc.elements["xml_api_reply/weather/forecast_information/current_date_time"]
    time = node.attribute("data").to_s.to_time if node
    time > Regentanz.configuration.cache_ttl.seconds.ago
  rescue
    # TODO pass exception upstream until properly delegated in the first place?
  end
end

#waiting_for_retry? ⇒ Boolean

Returns whether or not weather retrieval from the API is currently waiting for a timeout to expire; here: existence of a retry marker file

Returns:

  • (Boolean) 


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# File 'lib/regentanz/cache/file.rb', line 62

def waiting_for_retry?
  ::File.exists?(Regentanz.configuration.retry_marker)
end