Class: NewRelic::Rack::BrowserMonitoring

Inherits:
Object
  • Object
show all
Defined in:
lib/new_relic/rack/browser_monitoring.rb

Constant Summary collapse

ALREADY_INSTRUMENTED_KEY = 
"newrelic.browser_monitoring_already_instrumented"

Instance Method Summary collapse

Constructor Details

#initialize(app, options = {}) ⇒ BrowserMonitoring

Returns a new instance of BrowserMonitoring.



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# File 'lib/new_relic/rack/browser_monitoring.rb', line 10

def initialize(app, options = {})
  @app = app
end

Instance Method Details

#autoinstrument_source(response, headers) ⇒ Object 



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# File 'lib/new_relic/rack/browser_monitoring.rb', line 42

def autoinstrument_source(response, headers)
  source = nil
  response.each {|fragment| source ? (source << fragment.to_s) : (source = fragment.to_s)}
  return nil unless source


  # Only scan the first 50k (roughly) then give up.
  beginning_of_source = source[0..50_000]
  # Don't scan for body close unless we find body start
  if (body_start = beginning_of_source.index("<body")) && (body_close = source.rindex("</body>"))

    footer = NewRelic::Agent.browser_timing_footer
    header = NewRelic::Agent.browser_timing_header

    x_ua_compatible_found = beginning_of_source.include?('X-UA-Compatible')

    head_pos = if x_ua_compatible_found
      # put at end of header if X-UA-Compatible meta tag found
      ::NewRelic::Agent.logger.debug "Detected X-UA-Compatible meta tag. Attempting to insert RUM header at end of head."
      beginning_of_source.index("</head>")
    elsif head_open = beginning_of_source.index("<head")
      ::NewRelic::Agent.logger.debug "Attempting to insert RUM header at beginning of head."
      # put at the beginning of the header
      beginning_of_source.index(">", head_open) + 1
    else
      ::NewRelic::Agent.logger.debug "Failed to detect head tag. Attempting to insert RUM header at above body tag."
      # otherwise put the header right above body start
      body_start
    end

    # check that head_pos is less than body close.  If it's not something
    # is really weird and we should punt.
    if head_pos && (head_pos < body_close)
      # rebuild the source
      source = source[0..(head_pos-1)] <<
        header <<
        source[head_pos..(body_close-1)] <<
        footer <<
        source[body_close..-1]
    else
      if head_pos
        ::NewRelic::Agent.logger.debug "Skipping RUM instrumentation. Failed to detect head tags."
      else
        ::NewRelic::Agent.logger.debug "Skipping RUM instrumentation. Detected head is after detected body close."
      end
    end
  end
  headers['Content-Length'] = source.length.to_s if headers['Content-Length']
  source
end

#call(env) ⇒ Object

method required by Rack interface



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# File 'lib/new_relic/rack/browser_monitoring.rb', line 15

def call(env)
  result = @app.call(env)   # [status, headers, response]

  if (NewRelic::Agent.browser_timing_header != "") && should_instrument?(env, result[0], result[1])
    response_string = autoinstrument_source(result[2], result[1])

    env[ALREADY_INSTRUMENTED_KEY] = true
    if response_string
      response = Rack::Response.new(response_string, result[0], result[1])
      response.finish
    else
      result
    end
  else
    result
  end
end

#should_instrument?(env, status, headers) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/new_relic/rack/browser_monitoring.rb', line 35

def should_instrument?(env, status, headers)
  status == 200 &&
    !env[ALREADY_INSTRUMENTED_KEY] &&
    headers["Content-Type"] && headers["Content-Type"].include?("text/html") &&
    !headers['Content-Disposition'].to_s.include?('attachment')
end