Class: HeapScope::Flamegraph

Inherits:
Object
  • Object
show all
Defined in:
lib/heapscope/flamegraph.rb

Overview

Turns snapshot allocation sites into folded stacks or Speedscope JSON.

Folded output is compatible with inferno / flamegraph.pl. Speedscope JSON can be dropped onto https://www.speedscope.app (local file, no upload required by HeapScope itself).

Defined Under Namespace

Classes: Frame

Constant Summary collapse

FORMATS = 
%i[folded speedscope].freeze

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(frames:, snapshot_id: nil, unit: :count) ⇒ Flamegraph

Returns a new instance of Flamegraph.



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# File 'lib/heapscope/flamegraph.rb', line 16

def initialize(frames:, snapshot_id: nil, unit: :count)
  @frames = frames
  @snapshot_id = snapshot_id
  @unit = unit
end

Instance Attribute Details

#frames ⇒ Object (readonly)

Returns the value of attribute frames.



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# File 'lib/heapscope/flamegraph.rb', line 14

def frames
  @frames
end

#snapshot_id ⇒ Object (readonly)

Returns the value of attribute snapshot_id.



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# File 'lib/heapscope/flamegraph.rb', line 14

def snapshot_id
  @snapshot_id
end

#unit ⇒ Object (readonly)

Returns the value of attribute unit.



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# File 'lib/heapscope/flamegraph.rb', line 14

def unit
  @unit
end

Class Method Details

.from_snapshot(snapshot, unit: :count) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/heapscope/flamegraph.rb', line 22

def self.from_snapshot(snapshot, unit: :count)
  raise ArgumentError, "unit must be :count or :bytes" unless %i[count bytes].include?(unit.to_sym)

  snapshot = Snapshot.load(snapshot) if snapshot.is_a?(String)
  frames = []
  snapshot.allocation_sites.each do |site_key, stats|
    stats = symbolize(stats)
    site = stats[:site] || site_key.to_s
    method_id = stats[:method_id]
    classes = stats[:classes] || {}
    if classes.empty?
      frames << Frame.new(
        site: site,
        method_id: method_id,
        klass: nil,
        allocations: stats[:count].to_i,
        bytes: stats[:shallow_bytes].to_i
      )
    else
      classes.each do |klass, class_count|
        share = stats[:count].to_i.positive? ? (class_count.to_f / stats[:count]) : 0.0
        frames << Frame.new(
          site: site,
          method_id: method_id,
          klass: klass.to_s,
          allocations: class_count.to_i,
          bytes: (stats[:shallow_bytes].to_i * share).round
        )
      end
    end
  end
  new(frames: frames.sort_by { |frame| [-value_for(frame, unit), frame.site.to_s] },
      snapshot_id: snapshot.id, unit: unit.to_sym)
end

Instance Method Details

#empty? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/heapscope/flamegraph.rb', line 57

def empty?
  frames.empty? || total.zero?
end

#render(format: :folded) ⇒ Object

Raises:

  • (ArgumentError) 


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# File 'lib/heapscope/flamegraph.rb', line 115

def render(format: :folded)
  format = format.to_sym
  raise ArgumentError, "unknown flamegraph format #{format}" unless FORMATS.include?(format)

  format == :speedscope ? JSON.pretty_generate(to_speedscope) : to_folded
end

#to_folded ⇒ Object 



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# File 'lib/heapscope/flamegraph.rb', line 65

def to_folded
  frames.filter_map do |frame|
    weight = value_for(frame, unit)
    next if weight <= 0

    "#{stack_for(frame)} #{weight}"
  end.join("\n")
end

#to_h ⇒ Object 



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# File 'lib/heapscope/flamegraph.rb', line 122

def to_h
  {
    snapshot_id: snapshot_id,
    unit: unit,
    total: total,
    frames: frames.map do |frame|
      {
        site: frame.site,
        method_id: frame.method_id,
        class: frame.klass,
        count: frame.allocations,
        bytes: frame.bytes,
        stack: stack_for(frame)
      }
    end
  }
end

#to_speedscope ⇒ Object 



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# File 'lib/heapscope/flamegraph.rb', line 74

def to_speedscope
  names = []
  name_index = {}
  samples = []
  weights = []

  frames.each do |frame|
    weight = value_for(frame, unit)
    next if weight <= 0

    stack = []
    stack_for(frame).split(";").each do |name|
      unless name_index.key?(name)
        name_index[name] = names.length
        names << name
      end
      stack << name_index[name]
    end
    samples << stack
    weights << weight
  end

  {
    "$schema" => "https://www.speedscope.app/file-format-schema.json",
    shared: { frames: names.map { |name| { name: name } } },
    profiles: [
      {
        type: "sampled",
        name: "HeapScope allocations (#{unit})",
        unit: unit == :bytes ? "bytes" : "none",
        startValue: 0,
        endValue: weights.sum,
        samples: samples,
        weights: weights
      }
    ],
    exporter: "heapscope #{VERSION}",
    name: snapshot_id && "heapscope-#{snapshot_id}"
  }.compact
end

#total ⇒ Object 



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# File 'lib/heapscope/flamegraph.rb', line 61

def total
  frames.sum { |frame| value_for(frame, unit) }
end