Class: ActiveRecord::Turntable::Algorithm::RangeAlgorithm

Inherits:
Base
  • Object
show all
Defined in:
lib/active_record/turntable/algorithm/range_algorithm.rb

Instance Method Summary collapse

Constructor Details

#initialize(config) ⇒ RangeAlgorithm 



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# File 'lib/active_record/turntable/algorithm/range_algorithm.rb', line 4

def initialize(config)
  @config = config
end

Instance Method Details

#calculate(key) ⇒ Object 



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# File 'lib/active_record/turntable/algorithm/range_algorithm.rb', line 8

def calculate(key)
  idx = calculate_idx(key)
  @config[:shards][idx][:connection]
rescue
  raise ActiveRecord::Turntable::CannotSpecifyShardError, "cannot specify shard for key:#{key}"
end

#calculate_idx(key) ⇒ Object 



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# File 'lib/active_record/turntable/algorithm/range_algorithm.rb', line 15

def calculate_idx(key)
  @config[:shards].find_index { |h| h[:less_than] > key }
end

#calculate_used_shards_with_weight(sequence_value) ⇒ Object

{ connection_name => weight, … }



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# File 'lib/active_record/turntable/algorithm/range_algorithm.rb', line 20

def calculate_used_shards_with_weight(sequence_value)
  current_shard_idx = calculate_idx(sequence_value)
  shards = @config[:shards][0..current_shard_idx]
  weighted_hash = Hash.new { |h, k| h[k] = 0 }
  prev_max = 0
  shards.each_with_index do |h, idx|
    weighted_hash[h[:connection]] += if idx < shards.size - 1
                                       h[:less_than] - prev_max - 1
                                     else
                                       sequence_value - prev_max
                                     end
    prev_max = h[:less_than] - 1
  end
  weighted_hash
end