Class: Datadog::Profiling::Pprof::StackSample

Inherits:
Converter
  • Object
show all
Defined in:
lib/datadog/profiling/pprof/stack_sample.rb

Overview

Builds a profile from a StackSample

NOTE: This class may appear stateless but is in fact stateful; a new instance should be created for every encoded profile.

Constant Summary collapse

SAMPLE_TYPES = 
{
  cpu_time_ns: [
    Profiling::Ext::Pprof::VALUE_TYPE_CPU,
    Profiling::Ext::Pprof::VALUE_UNIT_NANOSECONDS
  ],
  wall_time_ns: [
    Profiling::Ext::Pprof::VALUE_TYPE_WALL,
    Profiling::Ext::Pprof::VALUE_UNIT_NANOSECONDS
  ]
}.freeze

Instance Attribute Summary

Attributes inherited from Converter

#builder

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Converter

#group_events, #sample_value_index

Constructor Details

#initialize(*_) ⇒ StackSample 



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 29

def initialize(*_)
  super

  @most_recent_trace_samples = {}
  @processed_unique_stacks = 0
  @processed_with_trace = 0
end

Class Method Details

.sample_value_types ⇒ Object 



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 25

def self.sample_value_types
  SAMPLE_TYPES
end

Instance Method Details

#add_events!(stack_samples) ⇒ Object 



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 37

def add_events!(stack_samples)
  new_samples = build_samples(stack_samples)
  builder.samples.concat(new_samples)
end

#build_event_values(stack_sample) ⇒ Object 



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 86

def build_event_values(stack_sample)
  no_value = Profiling::Ext::Pprof::SAMPLE_VALUE_NO_VALUE
  values = super(stack_sample)
  values[sample_value_index(:cpu_time_ns)] = stack_sample.cpu_time_interval_ns || no_value
  values[sample_value_index(:wall_time_ns)] = stack_sample.wall_time_interval_ns || no_value
  values
end

#build_sample(stack_sample, values) ⇒ Object 



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 73

def build_sample(stack_sample, values)
  locations = builder.build_locations(
    stack_sample.frames,
    stack_sample.total_frame_count
  )

  Perftools::Profiles::Sample.new(
    location_id: locations.collect { |location| location['id'.freeze] },
    value: values,
    label: build_sample_labels(stack_sample)
  )
end

#build_sample_labels(stack_sample) ⇒ Object 



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 94

def build_sample_labels(stack_sample)
  labels = [
    Perftools::Profiles::Label.new(
      key: builder.string_table.fetch(Profiling::Ext::Pprof::LABEL_KEY_THREAD_ID),
      str: builder.string_table.fetch(stack_sample.thread_id.to_s)
    )
  ]

  root_span_id = stack_sample.root_span_id || 0
  span_id = stack_sample.span_id || 0

  if root_span_id != 0 && span_id != 0
    @processed_with_trace += 1

    labels << Perftools::Profiles::Label.new(
      key: builder.string_table.fetch(Profiling::Ext::Pprof::LABEL_KEY_LOCAL_ROOT_SPAN_ID),
      str: builder.string_table.fetch(root_span_id.to_s)
    )

    labels << Perftools::Profiles::Label.new(
      key: builder.string_table.fetch(Profiling::Ext::Pprof::LABEL_KEY_SPAN_ID),
      str: builder.string_table.fetch(span_id.to_s)
    )

    # Use most up-to-date trace resource, if available.
    # Otherwise, use the trace resource provided.
    trace_resource = @most_recent_trace_samples.fetch(stack_sample.root_span_id, stack_sample).trace_resource

    if trace_resource && !trace_resource.empty?
      labels << Perftools::Profiles::Label.new(
        key: builder.string_table.fetch(Profiling::Ext::Pprof::LABEL_KEY_TRACE_ENDPOINT),
        str: builder.string_table.fetch(trace_resource)
      )
    end
  end

  labels
end

#build_samples(stack_samples) ⇒ Object 



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 65

def build_samples(stack_samples)
  groups = group_events(stack_samples, &method(:stack_sample_group_key))
  groups.collect do |_group_key, group|
    @processed_unique_stacks += 1
    build_sample(group.sample, group.values)
  end
end

#debug_statistics ⇒ Object 



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 133

def debug_statistics
  "unique stacks: #{@processed_unique_stacks}, of which had active traces: #{@processed_with_trace}"
end

#stack_sample_group_key(stack_sample) ⇒ Object 



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 42

def stack_sample_group_key(stack_sample)
  # We want to make sure we have the most recent sample for any trace.
  # (This is done here to save an iteration over all samples.)
  update_most_recent_trace_sample(stack_sample)

  stack_sample.hash
end

#update_most_recent_trace_sample(stack_sample) ⇒ Object

Track the most recent sample for each trace (identified by root span id)



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# File 'lib/datadog/profiling/pprof/stack_sample.rb', line 51

def update_most_recent_trace_sample(stack_sample)
  return unless stack_sample.root_span_id && stack_sample.trace_resource

  # Update trace resource with most recent value
  if (most_recent_trace_sample = @most_recent_trace_samples[stack_sample.root_span_id])
    if most_recent_trace_sample.timestamp < stack_sample.timestamp
      @most_recent_trace_samples[stack_sample.root_span_id] = stack_sample
    end
  else
    # Add trace resource
    @most_recent_trace_samples[stack_sample.root_span_id] = stack_sample
  end
end