Use binary search for histogram buckets

Author: simpl1g

lib/prometheus/client/histogram.rb

@@ -1,4 +1,4 @@
-# encoding: UTF-8
+# frozen_string_literal: true
 
 require 'prometheus/client/metric'
 
@@ -37,8 +37,8 @@ def self.linear_buckets(start:, width:, count:)
         count.times.map { |idx| start.to_f + idx * width }
       end
 
-      def self.exponential_buckets(start:, factor: 2, count:)
-        count.times.map { |idx| start.to_f * factor ** idx }
+      def self.exponential_buckets(start:, count:, factor: 2)
+        count.times.map { |idx| start.to_f * factor**idx }
       end
 
       def with_labels(labels)
@@ -67,16 +67,16 @@ def type
       # https://prometheus.io/docs/practices/histograms/#count-and-sum-of-observations
       # for details.
       def observe(value, labels: {})
-        bucket = buckets.find {|upper_limit| upper_limit >= value  }
-        bucket = "+Inf" if bucket.nil?
+        bucket = buckets.bsearch { |upper_limit| upper_limit >= value }
+        bucket = '+Inf' if bucket.nil?
 
         base_label_set = label_set_for(labels)
 
         # This is basically faster than doing `.merge`
         bucket_label_set = base_label_set.dup
         bucket_label_set[:le] = bucket.to_s
         sum_label_set = base_label_set.dup
-        sum_label_set[:le] = "sum"
+        sum_label_set[:le] = 'sum'
 
         @store.synchronize do
           @store.increment(labels: bucket_label_set, by: 1)
@@ -88,7 +88,7 @@ def observe(value, labels: {})
       def get(labels: {})
         base_label_set = label_set_for(labels)
 
-        all_buckets = buckets + ["+Inf", "sum"]
+        all_buckets = buckets + ['+Inf', 'sum']
 
         @store.synchronize do
           all_buckets.each_with_object({}) do |upper_limit, acc|
@@ -104,8 +104,8 @@ def values
         values = @store.all_values
 
         result = values.each_with_object({}) do |(label_set, v), acc|
-          actual_label_set = label_set.reject{|l| l == :le }
-          acc[actual_label_set] ||= @buckets.map{|b| [b.to_s, 0.0]}.to_h
+          actual_label_set = label_set.reject { |l| l == :le }
+          acc[actual_label_set] ||= @buckets.map { |b| [b.to_s, 0.0] }.to_h
           acc[actual_label_set][label_set[:le].to_s] = v
         end
 
@@ -118,7 +118,7 @@ def init_label_set(labels)
         base_label_set = label_set_for(labels)
 
         @store.synchronize do
-          (buckets + ["+Inf", "sum"]).each do |bucket|
+          (buckets + ['+Inf', 'sum']).each do |bucket|
             @store.set(labels: base_label_set.merge(le: bucket.to_s), val: 0)
           end
         end
@@ -135,8 +135,8 @@ def accumulate_buckets(h)
           bucket_acc += bucket_value
         end
 
-        inf_value = h["+Inf"] || 0.0
-        h["+Inf"] = inf_value + bucket_acc
+        inf_value = h['+Inf'] || 0.0
+        h['+Inf'] = inf_value + bucket_acc
       end
 
       def reserved_labels