Module: Philiprehberger::FeatureFlag::Rollout

Defined in:
lib/philiprehberger/feature_flag/rollout.rb

Class Method Summary collapse

Class Method Details

.bucket_key(user_id, context, rollout_by) ⇒ String?

Build the bucket key from user_id and context guided by rollout_by. When rollout_by is [:user_id] (the default) and the user id is missing, returns nil to preserve the historic “nil user_id disables rollout” behavior.

Returns:

  • (String, nil) 


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# File 'lib/philiprehberger/feature_flag/rollout.rb', line 43

def bucket_key(user_id, context, rollout_by)
  keys = Array(rollout_by).map(&:to_sym)
  keys = [:user_id] if keys.empty?

  if keys == [:user_id]
    return nil if user_id.nil?

    return user_id.to_s
  end

  parts = keys.map do |k|
    if k == :user_id
      user_id
    else
      context[k] || context[k.to_s]
    end
  end
  return nil if parts.all?(&:nil?)

  parts.join('|')
end

.enabled_for?(flag, user_id, percentage, context: {}, rollout_by: [:user_id]) ⇒ Boolean

Determine whether flag is enabled for a user given a percentage rollout. The bucket key defaults to the user id, matching the historic behavior. Pass rollout_by to mix additional context values into the bucket key — e.g. rollout_by: [:user_id, :region] assigns a user differently per region.

Parameters:

  • flag (Symbol, String) —

    flag name

  • user_id (String, Integer, nil) —

    primary bucket key

  • percentage (Integer, nil) —

    rollout percentage in 0..100

  • context (Hash) (defaults to: {}) —

    optional context hash whose values may be combined into the bucket key via rollout_by

  • rollout_by (Array<Symbol>) (defaults to: [:user_id]) —

    ordered list of context keys (plus the implicit :user_id) that form the bucket key. Defaults to [:user_id] — preserving historic behavior.

Returns:

  • (Boolean) 


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# File 'lib/philiprehberger/feature_flag/rollout.rb', line 25

def enabled_for?(flag, user_id, percentage, context: {}, rollout_by: [:user_id])
  return false if percentage.nil?
  return false if percentage <= 0
  return true if percentage >= 100

  key = bucket_key(user_id, context, rollout_by)
  return false if key.nil?

  bucket = Zlib.crc32("#{flag}:#{key}") % 100
  bucket < percentage
end