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require 'logger'
module Gitlab
module Metrics
class BaseSampler
def self.initialize_instance(*args)
raise "#{name} singleton instance already initialized" if @instance
@instance = new(*args)
at_exit(&@instance.method(:stop))
@instance
end
def self.instance
@instance
end
attr_reader :running
# interval - The sampling interval in seconds.
def initialize(interval)
interval_half = interval.to_f / 2
@interval = interval
@interval_steps = (-interval_half..interval_half).step(0.1).to_a
@mutex = Mutex.new
end
def enabled?
true
end
def start
return unless enabled?
@mutex.synchronize do
return if running
@running = true
@thread = Thread.new do
sleep(sleep_interval)
while running
safe_sample
sleep(sleep_interval)
end
end
end
end
def stop
@mutex.synchronize do
return unless running
@running = false
if @thread
@thread.wakeup if @thread.alive?
@thread.join
@thread = nil
end
end
end
def safe_sample
sample
rescue => e
Rails.logger.warn("#{self.class}: #{e}, stopping")
stop
end
def sample
raise NotImplementedError
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
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