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

Defined in:
lib/datadog/tracing/contrib/rack/request_queue.rb

Overview

Retrieves the time spent in an upstream proxy for the current Rack request.

This time captures the request delay introduced but such proxy before the request made it to the Ruby process.

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/datadog/tracing/contrib/rack/request_queue.rb', line 18

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.logger.debug("[rack] unable to parse request queue headers: #{e}")
  nil
end