Class: ScoutApm::Layer

Inherits:
Object
  • Object
show all
Defined in:
lib/scout_apm/layer.rb

Constant Summary collapse

BACKTRACE_CALLER_LIMIT =

maximum number of lines to send thru for backtrace analysis

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Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(type, name, start_time = Time.now) ⇒ Layer

Returns a new instance of Layer.



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# File 'lib/scout_apm/layer.rb', line 45

def initialize(type, name, start_time = Time.now)
  @type = type
  @name = name
  @annotations = {}
  @start_time = start_time
  @allocations_start = ScoutApm::Instruments::Allocations.count
  @allocations_stop = 0
  @children = [] # In order of calls
  @desc = nil
end

Instance Attribute Details

#annotations ⇒ Object (readonly)

As we go through a part of a request, instrumentation can store additional data Known Keys:

:record_count - The number of rows returned by an AR query (From notification instantiation.active_record)
:class_name   - The ActiveRecord class name (From notification instantiation.active_record)



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# File 'lib/scout_apm/layer.rb', line 41

def annotations
  @annotations
end

#backtrace ⇒ Object (readonly)

If this layer took longer than a fixed amount of time, store the backtrace of where it occurred.



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# File 'lib/scout_apm/layer.rb', line 35

def backtrace
  @backtrace
end

#children ⇒ Object (readonly)

An array of children layers, in call order. For instance, if we are in a middleware, there will likely be only a single child, which is another middleware. In a Controller, we may have a handful of children: [ActiveRecord, ActiveRecord, View, HTTP Call].

This useful to get actual time spent in this layer vs. children time



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# File 'lib/scout_apm/layer.rb', line 22

def children
  @children
end

#desc ⇒ Object

The description of this layer. Will contain additional details specific to the type of layer. For an ActiveRecord metric, it will contain the SQL run For an outoing HTTP call, it will contain the remote URL accessed Leave blank if there is nothing to note



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# File 'lib/scout_apm/layer.rb', line 31

def desc
  @desc
end

#name ⇒ Object

Name: a more specific name of this single item

Examples: "Rack::Cache", "User#find", "users/index", "users/index.html.erb"

Accessor, so we can update a layer if multiple pieces of instrumentation work

together at different layers to fill in the full data. See the ActiveRecord
instrumentation for an example of how this is useful



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# File 'lib/scout_apm/layer.rb', line 14

def name
  @name
end

#start_time ⇒ Object (readonly)

Time objects recording the start & stop times of this layer



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# File 'lib/scout_apm/layer.rb', line 25

def start_time
  @start_time
end

#stop_time ⇒ Object (readonly)

Time objects recording the start & stop times of this layer



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# File 'lib/scout_apm/layer.rb', line 25

def stop_time
  @stop_time
end

#type ⇒ Object (readonly)

Type: a general name for the kind of thing being tracked.

Examples: "Middleware", "ActiveRecord", "Controller", "View"



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# File 'lib/scout_apm/layer.rb', line 6

def type
  @type
end

Instance Method Details

#add_child(child) ⇒ Object 



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# File 'lib/scout_apm/layer.rb', line 56

def add_child(child)
  @children << child
end

#annotate_layer(hsh) ⇒ Object

This data is internal to ScoutApm, to add custom information, use the Context api.



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# File 'lib/scout_apm/layer.rb', line 74

def annotate_layer(hsh)
  @annotations.merge!(hsh)
end

#caller_array ⇒ Object

In Ruby 2.0+, we can pass the range directly to the caller to reduce the memory footprint.



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# File 'lib/scout_apm/layer.rb', line 98

def caller_array
  # omits the first several callers which are in the ScoutAPM stack.
  if ScoutApm::Environment.instance.ruby_2?
    caller(3...BACKTRACE_CALLER_LIMIT)
  else
    caller[3...BACKTRACE_CALLER_LIMIT]
  end
end

#capture_backtrace! ⇒ Object 



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# File 'lib/scout_apm/layer.rb', line 93

def capture_backtrace!
  @backtrace = caller_array
end

#child_allocations ⇒ Object 



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# File 'lib/scout_apm/layer.rb', line 167

def child_allocations
  children.
    map { |child| child.total_allocations }.
    inject(0) { |sum, obj| sum + obj }
end

#child_time ⇒ Object 



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# File 'lib/scout_apm/layer.rb', line 142

def child_time
  children.
    map { |child| child.total_call_time }.
    inject(0) { |sum, time| sum + time }
end

#legacy_metric_name ⇒ Object

This is the old style name. This function is used for now, but should be removed, and the new type & name split should be enforced through the app.



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# File 'lib/scout_apm/layer.rb', line 89

def legacy_metric_name
  "#{type}/#{name}"
end

#record_allocations! ⇒ Object

Fetch the current number of allocated objects. This will always increment - we fetch when initializing and when stopping the layer.



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# File 'lib/scout_apm/layer.rb', line 65

def record_allocations!
  @allocations_stop = ScoutApm::Instruments::Allocations.count
end

#record_stop_time!(stop_time = Time.now) ⇒ Object 



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# File 'lib/scout_apm/layer.rb', line 60

def record_stop_time!(stop_time = Time.now)
  @stop_time = stop_time
end

#subscopable! ⇒ Object 



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# File 'lib/scout_apm/layer.rb', line 78

def subscopable!
  @subscopable = true
end

#subscopable? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/scout_apm/layer.rb', line 82

def subscopable?
  @subscopable
end

#to_s ⇒ Object

May not be safe to call in every rails app, relies on Time#iso8601



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# File 'lib/scout_apm/layer.rb', line 112

def to_s
  name_clause = "#{type}/#{name}"

  total_string = total_call_time == 0 ? nil : "Total: #{total_call_time}"
  self_string = total_exclusive_time == 0 ? nil : "Self: #{total_exclusive_time}"
  timing_string = [total_string, self_string].compact.join(", ")

  time_clause = "(Start: #{start_time.iso8601} / Stop: #{stop_time.try(:iso8601)} [#{timing_string}])"
  desc_clause = "Description: #{desc.inspect}"
  children_clause = "Children: #{children.length}"

  "<Layer: #{name_clause} #{time_clause} #{desc_clause} #{children_clause}>"
end

#total_allocations ⇒ Object

These are almost identical to the timing metrics.



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# File 'lib/scout_apm/layer.rb', line 154

def total_allocations
  if @allocations_stop > 0
    allocations = (@allocations_stop - @allocations_start)
  else
    allocations = (ScoutApm::Instruments::Allocations.count - @allocations_start)
  end
  allocations < 0 ? 0 : allocations
end

#total_call_time ⇒ Object

Time Calculations



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# File 'lib/scout_apm/layer.rb', line 130

def total_call_time
  if stop_time
    stop_time - start_time
  else
    Time.now - start_time
  end
end

#total_exclusive_allocations ⇒ Object 



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# File 'lib/scout_apm/layer.rb', line 163

def total_exclusive_allocations
  total_allocations - child_allocations
end

#total_exclusive_time ⇒ Object 



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# File 'lib/scout_apm/layer.rb', line 138

def total_exclusive_time
  total_call_time - child_time
end