Module: Datadog::Contrib::Rack::QueueTime

Defined in:
lib/ddtrace/contrib/rack/request_queue.rb

Overview

QueueTime simply…

Constant Summary collapse

REQUEST_START = 
'HTTP_X_REQUEST_START'.freeze
QUEUE_START = 
'HTTP_X_QUEUE_START'.freeze
MINIMUM_ACCEPTABLE_TIME_VALUE = 
1_000_000_000

Class Method Summary collapse

Class Method Details

.get_request_start(env, now = Time.now.utc) ⇒ Object 



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# File 'lib/ddtrace/contrib/rack/request_queue.rb', line 12

def get_request_start(env, now = Time.now.utc)
  header = env[REQUEST_START] || env[QUEUE_START]
  return unless header

  # nginx header is seconds in the format "t=1512379167.574"
  # apache header is microseconds in the format "t=1570633834463123"
  # heroku header is milliseconds in the format "1570634024294"
  time_string = header.to_s.delete('^0-9')
  return if time_string.nil?

  # Return nil if the time is clearly invalid
  time_value = "#{time_string[0, 10]}.#{time_string[10, 6]}".to_f
  return if time_value.zero? || time_value < MINIMUM_ACCEPTABLE_TIME_VALUE

  # return the request_start only if it's lesser than
  # current time, to avoid significant clock skew
  request_start = Time.at(time_value)
  request_start.utc > now ? nil : request_start
rescue StandardError => e
  # in case of an Exception we don't create a
  # `request.queuing` span
  Datadog::Tracer.log.debug("[rack] unable to parse request queue headers: #{e}")
  nil
end