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# encoding: UTF-8
module Prometheus
module Client
# LabelSetValidator ensures that all used label sets comply with the
# Prometheus specification.
class LabelSetValidator
RESERVED_LABELS = [].freeze
class LabelSetError < StandardError; end
class InvalidLabelSetError < LabelSetError; end
class InvalidLabelError < LabelSetError; end
class ReservedLabelError < LabelSetError; end
def initialize(reserved_labels = [])
@reserved_labels = (reserved_labels + RESERVED_LABELS).freeze
@validated = {}
end
def valid?(labels)
unless labels.is_a?(Hash)
raise InvalidLabelSetError, "#{labels} is not a valid label set"
end
labels.all? do |key, value|
validate_symbol(key)
validate_name(key)
validate_reserved_key(key)
validate_value(key, value)
end
end
def validate(labels)
return labels if @validated.key?(labels.hash)
valid?(labels)
unless @validated.empty? || match?(labels, @validated.first.last)
raise InvalidLabelSetError, "labels must have the same signature: (#{label_diff(labels, @validated.first.last)})"
end
@validated[labels.hash] = labels
end
private
def label_diff(a, b)
"expected keys: #{b.keys.sort}, got: #{a.keys.sort}"
end
def match?(a, b)
a.keys.sort == b.keys.sort
end
def validate_symbol(key)
return true if key.is_a?(Symbol)
raise InvalidLabelError, "label #{key} is not a symbol"
end
def validate_name(key)
return true unless key.to_s.start_with?('__')
raise ReservedLabelError, "label #{key} must not start with __"
end
def validate_reserved_key(key)
return true unless @reserved_labels.include?(key)
raise ReservedLabelError, "#{key} is reserved"
end
def validate_value(key, value)
return true if value.is_a?(String) ||
value.is_a?(Numeric) ||
value.is_a?(Symbol) ||
value.is_a?(FalseClass) ||
value.is_a?(TrueClass) ||
value.nil?
raise InvalidLabelError, "#{key} does not contain a valid value (type #{value.class})"
end
end
end
end
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