remove prometheus sampler

lib/gitlab/metrics/prometheus_sampler.rb

-module Gitlab
-  module Metrics
-    # Class that sends certain metrics to InfluxDB at a specific interval.
-    #
-    # This class is used to gather statistics that can't be directly associated
-    # with a transaction such as system memory usage, garbage collection
-    # statistics, etc.
-    class PrometheusSamples
-      # interval - The sampling interval in seconds.
-      def initialize(interval = Metrics.settings[:sample_interval])
-        interval_half = interval.to_f / 2
-
-        @interval = interval
-        @interval_steps = (-interval_half..interval_half).step(0.1).to_a
-      end
-
-      def start
-        Thread.new do
-          Thread.current.abort_on_exception = true
-
-          loop do
-            sleep(sleep_interval)
-
-            sample
-          end
-        end
-      end
-
-      def sidekiq?
-        Sidekiq.server?
-      end
-
-      # Returns the sleep interval with a random adjustment.
-      #
-      # The random adjustment is put in place to ensure we:
-      #
-      # 1. Don't generate samples at the exact same interval every time (thus
-      #    potentially missing anything that happens in between samples).
-      # 2. Don't sample data at the same interval two times in a row.
-      def sleep_interval
-        while step = @interval_steps.sample
-          if step != @last_step
-            @last_step = step
-
-            return @interval + @last_step
-          end
-        end
-      end
-    end
-  end
-end