Class: MeterCat::Meter

Inherits:
ActiveRecord::Base
  • Object
show all
Defined in:
app/models/meter_cat/meter.rb

Constant Summary collapse

DEFAULT_EXPIRATION =

The expiration time for an in-memory cached meter

3600
DEFAULT_RETRY_ATTEMPTS =

The number of retries in the event of an optimistic locking failure or creation collision

5
DEFAULT_RETRY_DELAY =

The delay between retries, in seconds. Not using exponential back-off to prevent blocking controllers. Better to lose a little data than create a bad user experience.

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Class Method Summary collapse

Instance Method Summary collapse

Class Method Details

.names ⇒ Object

Returns all unique meter names sorted



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# File 'app/models/meter_cat/meter.rb', line 71

def self.names
  Meter.uniq.pluck( :name ).sort.map { |name| name.to_sym }
end

.random(args) ⇒ Object

Generates a random sequence for a meter given the following args:

:name, :min, :max, :days 


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# File 'app/models/meter_cat/meter.rb', line 78

def self.random( args )
  name = args[ :name ]
  min = args[ :min ].to_i
  max = args[ :max ].to_i
  stop = Date.today
  start = Date.today - args[ :days ].to_i

  (start .. stop).each do |date|
    value = min + rand( max - min )
    begin
      Meter.create( :name => name, :value => value, :created_on => date )
    rescue
    end
  end
end

.set(name, value = 1, created_on = Date.today) ⇒ Object

Sets or creates a new record for the name and day



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# File 'app/models/meter_cat/meter.rb', line 96

def self.set( name, value = 1, created_on = Date.today )
  meter = Meter.find_by_name_and_created_on( name, created_on )
  meter ||= Meter.new( :name => name, :created_on => created_on )
  meter.value = value
  return meter.save
end

.to_csv(range, names = nil) ⇒ Object

Returns a CSV where rows represent days



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# File 'app/models/meter_cat/meter.rb', line 137

def self.to_csv( range, names = nil  )
  meters = to_h( range, names )
  keys = meters.keys.sort!

  CSV.generate do |csv|
    csv << [ nil ] + keys
    range.each do |date|
      csv << [ date ] + keys.map { |key| meters[ key ][ date ] }
    end
  end
end

.to_h(range, names = nil) ⇒ Object

Returns a hash of names to dates to values



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# File 'app/models/meter_cat/meter.rb', line 105

def self.to_h( range, names = nil )
  meters = {}

  # Inject dependencies into the names array

  calculator = MeterCat.config.calculator
  calculator.dependencies( names ) if names

  # Build conditions for the query

  conditions = {}
  conditions[ :created_on ] = range if range
  conditions[ :name ] = names if names

  # Retrieve the data

  Meter.select( [ :id, :name, :created_on, :value ] ).where( conditions ).find_each do |meter|
    name = meter.name.to_sym
    meters[ name ] ||= {}
    meters[ name ][ meter.created_on ] = meter.value
  end

  # Fill in calculated and missing values

  calculator.calculate( meters, range, names )
  names.each { |name| meters[ name ] ||= {} } if names

  return meters
end

Instance Method Details

#add ⇒ Object

Create an object for this name+date in the db if one does not already exist. Add the value from this object to the one in the DB. Returns the result of the ActiveRecord save operation.



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# File 'app/models/meter_cat/meter.rb', line 34

def add
  meter = nil
  Meter.uncached { meter = Meter.find_by_name_and_created_on( name, created_on )}
  meter ||= Meter.new( :name => name, :created_on => created_on )
  meter.value += value
  return meter.save
end

#add_with_retry ⇒ Object

Calls #add with retry logic up to ::MAX_ADD_ATTEMPTS times. Catches ActiveRecord::StaleObjectError and ActiveRecord::RecordNotUnique for retries. Returns the result of the final call to #add



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# File 'app/models/meter_cat/meter.rb', line 46

def add_with_retry
  success = false

  (1..MeterCat.config.retry_attempts).each do
    begin
      break if success = add
    rescue ActiveRecord::StaleObjectError, ActiveRecord::RecordNotUnique
    end
    Kernel.sleep( MeterCat.config.retry_delay )
  end

  return success
end

#expired? ⇒ Boolean

Determines if the meter is expired and should be flushed from memory to DB

Returns:

  • (Boolean) 


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# File 'app/models/meter_cat/meter.rb', line 62

def expired?
  return ( Time.now - created_at ) > MeterCat.config.expiration
end