Module: Feat::Bucketing

Defined in:
lib/feat/bucketing.rb

Overview

Deterministic bucketing for percentage rollouts. Algorithm matches @feathq/feat-eval (JS), feat-go-sdk (Go), and feat (Python) bit-for-bit:

sha1(salt + "." + flag_key + "." + context_key)
-> first 8 bytes as big-endian uint64
-> shift right 4 (drop low bits) for exactly 60 bits
-> modulo 100_000

Constant Summary collapse

BUCKET_SCALE = 
100_000

Class Method Summary collapse

Class Method Details

.bucket(salt:, flag_key:, context_key:) ⇒ Object 



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# File 'lib/feat/bucketing.rb', line 17

def bucket(salt:, flag_key:, context_key:)
  digest = Digest::SHA1.digest("#{salt}.#{flag_key}.#{context_key}")
  first8 = digest[0, 8].unpack1("Q>") # big-endian unsigned 64-bit
  sixty = first8 >> 4
  sixty % BUCKET_SCALE
end

.pick_by_weight(bucket_value, variations) ⇒ Object

Walk cumulative weights; return the variation whose range contains bucket_value. Defensive fallback to the last variation if upstream weights underflow the scale.



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# File 'lib/feat/bucketing.rb', line 27

def pick_by_weight(bucket_value, variations)
  cumulative = 0
  variations.each do |v|
    cumulative += v.weight
    return v.variationId if bucket_value < cumulative
  end
  variations.empty? ? nil : variations.last.variationId
end