class Datadog::Span

Represents a logical unit of work in the system. Each trace consists of one or more spans. Each span consists of a start time and a duration. For example, a span can describe the time spent on a distributed call on a separate machine, or the time spent in a small component within a larger operation. Spans can be nested within each other, and in those instances will have a parent-child relationship.

rubocop:disable Metrics/ClassLength

Constants

ENSURE_AGENT_TAGS

Some associated values should always be sent as Tags, never as Metrics, regardless if their value is numeric or not. The Datadog agent will look for these values only as Tags, not Metrics. @see github.com/DataDog/datadog-agent/blob/2ae2cdd315bcda53166dd8fa0dedcfc448087b9d/pkg/trace/stats/aggregation.go#L13-L17

EXTERNAL_MAX_ID

While we only generate 63-bit integers due to limitations in other languages, we support parsing 64-bit integers for distributed tracing since an upstream system may generate one

NUMERIC_TAG_SIZE_RANGE

This limit is for numeric tags because uint64 could end up rounded.

RUBY_MAX_ID

The max value for a Span identifier. Span and trace identifiers should be strictly positive and strictly inferior to this limit.

Limited to +2<<62-1+ positive integers, as Ruby is able to represent such numbers “inline”, inside a VALUE scalar, thus not requiring memory allocation.

The range of IDs also has to consider portability across different languages and platforms.

ResourceContainer

Simple indirection used to contain the latest resource name for a span. The profiler keeps a reference to these objects while sampling so it can extract the latest resource after the fact, as some integrations only set the correct name at the end of the span.

Attributes

context[RW]
duration[W]
end_time[R]
name[RW]
parent[R]
parent_id[RW]
resource_container[R]
sampled[RW]
service[RW]
span_id[RW]
span_type[RW]
start_time[R]
status[RW]
trace_id[RW]
tracer[RW]

Public Class Methods

new(tracer, name, options = {}) click to toggle source

Create a new span linked to the given tracer. Call the Tracer method start_span() and then finish() once the tracer operation is over.

  • service: the service name for this span

  • resource: the resource this span refers, or name if it's missing

  • span_type: the type of the span (such as http, db and so on)

  • parent_id: the identifier of the parent span

  • trace_id: the identifier of the root span for this trace

  • context: the context of the span

# File lib/ddtrace/span.rb, line 79
def initialize(tracer, name, options = {})
  @tracer = tracer

  @name = name
  @service = options.fetch(:service, nil)
  @resource_container = ResourceContainer.new(options.fetch(:resource, name))
  @span_type = options.fetch(:span_type, nil)

  @span_id = Datadog::Utils.next_id
  @parent_id = options.fetch(:parent_id, 0)
  @trace_id = options.fetch(:trace_id, Datadog::Utils.next_id)

  @context = options.fetch(:context, nil)

  @meta = {}
  @metrics = {}
  @status = 0

  @parent = nil
  @sampled = true

  @allocation_count_start = now_allocations
  @allocation_count_finish = @allocation_count_start

  # start_time and end_time track wall clock. In Ruby, wall clock
  # has less accuracy than monotonic clock, so if possible we look to only use wall clock
  # to measure duration when a time is supplied by the user, or if monotonic clock
  # is unsupported.
  @start_time = nil
  @end_time = nil

  # duration_start and duration_end track monotonic clock, and may remain nil in cases where it
  # is known that we have to use wall clock to measure duration.
  @duration_start = nil
  @duration_end = nil
end

Public Instance Methods

allocations() click to toggle source
# File lib/ddtrace/span.rb, line 280
def allocations
  @allocation_count_finish - @allocation_count_start
end
clear_metric(key) click to toggle source

This method removes a metric for the given key. It acts like {#remove_tag}.

# File lib/ddtrace/span.rb, line 175
def clear_metric(key)
  @metrics.delete(key)
end
clear_tag(key) click to toggle source

This method removes a tag for the given key.

# File lib/ddtrace/span.rb, line 152
def clear_tag(key)
  @meta.delete(key)
end
duration() click to toggle source
# File lib/ddtrace/span.rb, line 409
def duration
  if @duration_end.nil? || @duration_start.nil?
    @end_time - @start_time
  else
    @duration_end - @duration_start
  end
end
end_time=(time) click to toggle source

for backwards compatibility

# File lib/ddtrace/span.rb, line 212
def end_time=(time)
  time.tap { finish(time) }
end
finish(finish_time = nil) click to toggle source

Mark the span finished at the current time and submit it.

# File lib/ddtrace/span.rb, line 217
def finish(finish_time = nil)
  # A span should not be finished twice. Note that this is not thread-safe,
  # finish is called from multiple threads, a given span might be finished
  # several times. Again, one should not do this, so this test is more a
  # fallback to avoid very bad things and protect you in most common cases.
  return if finished?

  @allocation_count_finish = now_allocations

  now = Utils::Time.now.utc

  # Provide a default start_time if unset.
  # Using `now` here causes duration to be 0; this is expected
  # behavior when start_time is unknown.
  start(finish_time || now) unless started?

  @end_time = finish_time || now
  @duration_end = finish_time.nil? ? duration_marker : nil

  # Finish does not really do anything if the span is not bound to a tracer and a context.
  return self if @tracer.nil? || @context.nil?

  # spans without a service would be dropped, so here we provide a default.
  # This should really never happen with integrations in contrib, as a default
  # service is always set. It's only for custom instrumentation.
  @service ||= (@tracer && @tracer.default_service)

  begin
    @context.close_span(self)
    @tracer.record(self)
  rescue StandardError => e
    Datadog.logger.debug("error recording finished trace: #{e}")
    Datadog.health_metrics.error_span_finish(1, tags: ["error:#{e.class.name}"])
  end
  self
end
finished?() click to toggle source

Return whether the duration is finished or not.

# File lib/ddtrace/span.rb, line 405
def finished?
  !@end_time.nil?
end
get_metric(key) click to toggle source

Return the metric with the given key, nil if it doesn't exist.

# File lib/ddtrace/span.rb, line 180
def get_metric(key)
  @metrics[key] || @meta[key]
end
get_tag(key) click to toggle source

Return the tag with the given key, nil if it doesn't exist.

# File lib/ddtrace/span.rb, line 157
def get_tag(key)
  @meta[key] || @metrics[key]
end
parent=(parent) click to toggle source

Set this span's parent, inheriting any properties not explicitly set. If the parent is nil, set the span zero values.

# File lib/ddtrace/span.rb, line 266
def parent=(parent)
  @parent = parent

  if parent.nil?
    @trace_id = @span_id
    @parent_id = 0
  else
    @trace_id = parent.trace_id
    @parent_id = parent.span_id
    @service ||= parent.service
    @sampled = parent.sampled
  end
end
pretty_print(q) click to toggle source

Return a human readable version of the span

# File lib/ddtrace/span.rb, line 367
def pretty_print(q)
  start_time = (self.start_time.to_f * 1e9).to_i
  end_time = (self.end_time.to_f * 1e9).to_i
  q.group 0 do
    q.breakable
    q.text "Name: #{@name}\n"
    q.text "Span ID: #{@span_id}\n"
    q.text "Parent ID: #{@parent_id}\n"
    q.text "Trace ID: #{@trace_id}\n"
    q.text "Type: #{@span_type}\n"
    q.text "Service: #{@service}\n"
    q.text "Resource: #{resource}\n"
    q.text "Error: #{@status}\n"
    q.text "Start: #{start_time}\n"
    q.text "End: #{end_time}\n"
    q.text "Duration: #{duration.to_f if finished?}\n"
    q.text "Allocations: #{allocations}\n"
    q.group(2, 'Tags: [', "]\n") do
      q.breakable
      q.seplist @meta.each do |key, value|
        q.text "#{key} => #{value}"
      end
    end
    q.group(2, 'Metrics: [', ']') do
      q.breakable
      q.seplist @metrics.each do |key, value|
        q.text "#{key} => #{value}"
      end
    end
  end
end
resource() click to toggle source
# File lib/ddtrace/span.rb, line 417
def resource
  @resource_container.latest
end
resource=(resource) click to toggle source
# File lib/ddtrace/span.rb, line 421
def resource=(resource)
  @resource_container.latest = resource
end
set_error(e) click to toggle source

Mark the span with the given error.

# File lib/ddtrace/span.rb, line 185
def set_error(e)
  e = Error.build_from(e)

  @status = Ext::Errors::STATUS
  set_tag(Ext::Errors::TYPE, e.type) unless e.type.empty?
  set_tag(Ext::Errors::MSG, e.message) unless e.message.empty?
  set_tag(Ext::Errors::STACK, e.backtrace) unless e.backtrace.empty?
end
set_metric(key, value) click to toggle source

This method sets a tag with a floating point value for the given key. It acts like `set_tag()` and it simply add a tag without further processing.

# File lib/ddtrace/span.rb, line 163
def set_metric(key, value)
  # Keys must be unique between tags and metrics
  @meta.delete(key)

  # enforce that the value is a floating point number
  value = Float(value)
  @metrics[key] = value
rescue StandardError => e
  Datadog.logger.debug("Unable to set the metric #{key}, ignoring it. Caused by: #{e}")
end
set_parent(parent) click to toggle source

DEPRECATED: remove this function in the next release, replaced by “parent=“

# File lib/ddtrace/span.rb, line 260
def set_parent(parent)
  self.parent = parent
end
set_tag(key, value = nil) click to toggle source

Set the given key / value tag pair on the span. Keys and values must be strings. A valid example is:

span.set_tag('http.method', request.method)
# File lib/ddtrace/span.rb, line 120
def set_tag(key, value = nil)
  # Keys must be unique between tags and metrics
  @metrics.delete(key)

  # DEV: This is necessary because the agent looks at `meta[key]`, not `metrics[key]`.
  value = value.to_s if ENSURE_AGENT_TAGS[key]

  # NOTE: Adding numeric tags as metrics is stop-gap support
  #       for numeric typed tags. Eventually they will become
  #       tags again.
  # Any numeric that is not an integer greater than max size is logged as a metric.
  # Everything else gets logged as a tag.
  if value.is_a?(Numeric) && !(value.is_a?(Integer) && !NUMERIC_TAG_SIZE_RANGE.cover?(value))
    set_metric(key, value)
  else
    @meta[key] = value.to_s
  end
rescue StandardError => e
  Datadog.logger.debug("Unable to set the tag #{key}, ignoring it. Caused by: #{e}")
end
set_tags(tags) click to toggle source

Sets tags from given hash, for each key in hash it sets the tag with that key and associated value from the hash. It is shortcut for `set_tag`. Keys and values of the hash must be strings. Note that nested hashes are not supported. A valid example is:

span.set_tags({ "http.method" => "GET", "user.id" => "234" })
# File lib/ddtrace/span.rb, line 147
def set_tags(tags)
  tags.each { |k, v| set_tag(k, v) }
end
start(start_time = nil) click to toggle source

Mark the span started at the current time.

# File lib/ddtrace/span.rb, line 195
def start(start_time = nil)
  # A span should not be started twice. However, this is existing
  # behavior and so we maintain it for backward compatibility for those
  # who are using async manual instrumentation that may rely on this

  @start_time = start_time || Utils::Time.now.utc
  @duration_start = start_time.nil? ? duration_marker : nil

  self
end
start_time=(time) click to toggle source

for backwards compatibility

# File lib/ddtrace/span.rb, line 207
def start_time=(time)
  time.tap { start(time) }
end
started?() click to toggle source

Return whether the duration is started or not

# File lib/ddtrace/span.rb, line 400
def started?
  !@start_time.nil?
end
to_hash() click to toggle source

Return the hash representation of the current span.

# File lib/ddtrace/span.rb, line 285
def to_hash
  h = {
    span_id: @span_id,
    parent_id: @parent_id,
    trace_id: @trace_id,
    name: @name,
    service: @service,
    resource: resource,
    type: @span_type,
    meta: @meta,
    metrics: @metrics,
    allocations: allocations,
    error: @status
  }

  if finished?
    h[:start] = start_time_nano
    h[:duration] = duration_nano
  end

  h
end
to_json(*args) click to toggle source

JSON serializer interface. Used by older version of the transport.

# File lib/ddtrace/span.rb, line 362
def to_json(*args)
  to_hash.to_json(*args)
end
to_msgpack(packer = nil) click to toggle source

MessagePack serializer interface. Making this object respond to `#to_msgpack` allows it to be automatically serialized by MessagePack.

This is more efficient than doing +MessagePack.pack(span.to_hash)+ as we don't have to create an intermediate Hash.

@param packer [MessagePack::Packer] serialization buffer, can be nil with JRuby

# File lib/ddtrace/span.rb, line 316
def to_msgpack(packer = nil)
  # As of 1.3.3, JRuby implementation doesn't pass an existing packer
  packer ||= MessagePack::Packer.new

  if finished?
    packer.write_map_header(13) # Set header with how many elements in the map

    packer.write('start')
    packer.write(start_time_nano)

    packer.write('duration')
    packer.write(duration_nano)
  else
    packer.write_map_header(11) # Set header with how many elements in the map
  end

  # DEV: We use strings as keys here, instead of symbols, as
  # DEV: MessagePack will ultimately convert them to strings.
  # DEV: By providing strings directly, we skip this indirection operation.
  packer.write('span_id')
  packer.write(@span_id)
  packer.write('parent_id')
  packer.write(@parent_id)
  packer.write('trace_id')
  packer.write(@trace_id)
  packer.write('name')
  packer.write(@name)
  packer.write('service')
  packer.write(@service)
  packer.write('resource')
  packer.write(resource)
  packer.write('type')
  packer.write(@span_type)
  packer.write('meta')
  packer.write(@meta)
  packer.write('metrics')
  packer.write(@metrics)
  packer.write('allocations')
  packer.write(allocations)
  packer.write('error')
  packer.write(@status)
  packer
end
to_s() click to toggle source

Return a string representation of the span.

# File lib/ddtrace/span.rb, line 255
def to_s
  "Span(name:#{@name},sid:#{@span_id},tid:#{@trace_id},pid:#{@parent_id})"
end

Private Instance Methods

duration_marker() click to toggle source
# File lib/ddtrace/span.rb, line 427
def duration_marker
  Utils::Time.get_time
end
duration_nano() click to toggle source

Used for serialization @return [Integer] in nanoseconds since Epoch

# File lib/ddtrace/span.rb, line 453
def duration_nano
  (duration * 1e9).to_i
end
now_allocations() click to toggle source
# File lib/ddtrace/span.rb, line 432
def now_allocations
  0
end
start_time_nano() click to toggle source

Used for serialization @return [Integer] in nanoseconds since Epoch

# File lib/ddtrace/span.rb, line 447
def start_time_nano
  @start_time.to_i * 1000000000 + @start_time.nsec
end