Class: Currency::Exchange::Rate::Source::TimedCache

Inherits:
Base
  • Object
show all
Defined in:
lib/currency/exchange/rate/source/timed_cache.rb

Overview

A timed cache for rate sources.

This class should be used at the top-level of a rate source change, to correctly check rate dates.

Instance Attribute Summary collapse

Attributes inherited from Base

#pivot_currency, #time_quantitizer, #verbose

Instance Method Summary collapse

Methods inherited from Base

#__subclass_responsibility, #clear_rate, #convert, #currencies, #get_rate_base, #get_rates, #new_rate, #normalize_time, #to_s

Constructor Details

#initialize(*opt) ⇒ TimedCache

Returns a new instance of TimedCache.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 43

def initialize(*opt)
  self.time_to_live = 600
  self.time_to_live_fudge = 30
  @rate_load_time = nil
  @rate_reload_time = nil
  @processing_rates = false
  @cached_rates = { }
  @cached_rates_old = nil
  super(*opt)
end

Instance Attribute Details

#rate_load_time ⇒ Object (readonly)

Returns the time of the last load.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 30

def rate_load_time
  @rate_load_time
end

#rate_reload_time ⇒ Object (readonly)

Returns the time of the next load.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 34

def rate_reload_time
  @rate_reload_time
end

#source ⇒ Object

The rate source.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 13

def source
  @source
end

#time_to_live ⇒ Object

Defines the number of seconds rates until rates become invalid, causing a request of new rates.

Defaults to 600 seconds.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 19

def time_to_live
  @time_to_live
end

#time_to_live_fudge ⇒ Object

Defines the number of random seconds to add before rates become invalid.

Defaults to 30 seconds.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 26

def time_to_live_fudge
  @time_to_live_fudge
end

Instance Method Details

#_calc_rate_reload_time ⇒ Object 



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 147

def _calc_rate_reload_time
  if @time_to_live && @rate_load_time
    @rate_reload_time = @rate_load_time + (@time_to_live + (@time_to_live_fudge || 0))
    $stderr.puts "#{self}: rates expire on #{@rate_reload_time}" if @verbose
  end

end

#_load_rates_from_source(time = nil) ⇒ Object

:nodoc:



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 157

def _load_rates_from_source(time = nil) # :nodoc:
  rates = nil

  begin
    # Do not allow re-entrancy
    raise Currency::Exception::InvalidReentrancy, "Reentry!" if @processing_rates
    
    # Begin processing new rate request.
    @processing_rates = true

    # Clear cached Rates.
    clear_rates

    # Load rates from the source.
    rates = source.load_rates(time)
    
    # Compute new rate timestamp.
    @rate_load_time = Time.now

    # STDERR.puts "rate_load_time = #{@rate_load_time}"
  ensure
    # End processsing new rate request.
    @processing_rates = false
  
  end

  # STDERR.puts "_load_rates => #{rates.inspect}"

  rates
end

#available?(time = nil) ⇒ Boolean

Returns true if the underlying rate provider is available.

Returns:

  • (Boolean) 


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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 190

def available?(time = nil)
  source.available?(time)
end

#clear_rates ⇒ Object

Clears current rates.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 56

def clear_rates
  @cached_rates = { }
  @source.clear_rates
  super
end

#expired? ⇒ Boolean

Returns true if the cache of Rates is expired.

Returns:

  • (Boolean) 


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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 65

def expired?
  if @time_to_live &&
      @rate_reload_time &&
      (Time.now > @rate_reload_time)
    
    if @cached_rates 
      $stderr.puts "#{self}: rates expired on #{@rate_reload_time}" if @verbose
      
      @cached_rates_old = @cached_rates
    end

    clear_rates
    
    true
  else
    false
  end
end

#get_rate(c1, c2, time) ⇒ Object 



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 94

def get_rate(c1, c2, time)
  # STDERR.puts "get_rate #{c1} #{c2} #{time}"
  rates = load_rates(time)
  # STDERR.puts "rates = #{rates.inspect}"
  rate = rates && (rates.select{|x| x.c1 == c1 && x.c2 == c2}[0])
  # STDERR.puts "rate = #{rate.inspect}"
  rate
end

#load_rates(time = nil) ⇒ Object

Returns an array of all the cached Rates.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 111

def load_rates(time = nil)
  # Check expiration.
  expired?
  
  # Return rates, if cached.
  return rates if rates = @cached_rates["#{time}"]
  
  # Force load of rates.
  rates = @cached_rates["#{time}"] = _load_rates_from_source(time)
  
  # Update expiration.
  _calc_rate_reload_time

  return nil unless rates

  # Flush old rates.
  @cached_rates_old = nil
      
  rates
end

#name ⇒ Object

Returns source’s name.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 38

def name
  source.name
end

#rate(c1, c2, time) ⇒ Object

Check expired? before returning a Rate.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 86

def rate(c1, c2, time)
  if expired?
    clear_rates
  end
  super(c1, c2, time)
end

#rates(time = nil) ⇒ Object

Returns an array of all the cached Rates.



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# File 'lib/currency/exchange/rate/source/timed_cache.rb', line 105

def rates(time = nil)
  load_rates(time)
end