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"
X_UA_COMPATIBLE_RE = 
/<\s*meta[^>]+http-equiv=['"]x-ua-compatible['"][^>]*>/im.freeze

Instance Method Summary collapse

Constructor Details

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

Returns a new instance of BrowserMonitoring.



10
11
12
 
# 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 



44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
 
# File 'lib/new_relic/rack/browser_monitoring.rb', line 44

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

    match = X_UA_COMPATIBLE_RE.match(beginning_of_source)
    x_ua_compatible_position = match.end(0) if match

    head_pos = if x_ua_compatible_position
      # put after X-UA-Compatible meta tag if found
      ::NewRelic::Agent.logger.debug "Detected X-UA-Compatible meta tag. Attempting to insert RUM header after meta tag."
      x_ua_compatible_position
    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



15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
 
# 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) 


35
36
37
38
39
40
 
# 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