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require 'prometheus/client/metric'
require 'prometheus/client/uses_value_type'
module Prometheus
module Client
# A histogram samples observations (usually things like request durations
# or response sizes) and counts them in configurable buckets. It also
# provides a sum of all observed values.
class Histogram < Metric
# Value represents the state of a Histogram at a given point.
class Value < Hash
include UsesValueType
attr_accessor :sum, :total, :total_inf
def initialize(type, name, labels, buckets)
@sum = value_object(type, name, "#{name}_sum", labels)
@total = value_object(type, name, "#{name}_count", labels)
@total_inf = value_object(type, name, "#{name}_bucket", labels.merge(le: "+Inf"))
buckets.each do |bucket|
self[bucket] = value_object(type, name, "#{name}_bucket", labels.merge(le: bucket.to_s))
end
end
def observe(value)
@sum.increment(value)
@total.increment()
@total_inf.increment()
each_key do |bucket|
self[bucket].increment() if value <= bucket
end
end
def get()
hash = {}
each_key do |bucket|
hash[bucket] = self[bucket].get()
end
hash
end
end
# DEFAULT_BUCKETS are the default Histogram buckets. The default buckets
# are tailored to broadly measure the response time (in seconds) of a
# network service. (From DefBuckets client_golang)
DEFAULT_BUCKETS = [0.005, 0.01, 0.025, 0.05, 0.1, 0.25, 0.5, 1,
2.5, 5, 10].freeze
# Offer a way to manually specify buckets
def initialize(name, docstring, base_labels = {},
buckets = DEFAULT_BUCKETS)
raise ArgumentError, 'Unsorted buckets, typo?' unless sorted? buckets
@buckets = buckets
super(name, docstring, base_labels)
end
def type
:histogram
end
def observe(labels, value)
label_set = label_set_for(labels)
synchronize { @values[label_set].observe(value) }
end
private
def default(labels)
# TODO: default function needs to know key of hash info (label names and values)
Value.new(type, @name, labels, @buckets)
end
def sorted?(bucket)
bucket.each_cons(2).all? { |i, j| i <= j }
end
end
end
end
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