Class: Datadog::Span

Inherits:
Object
  • Object
show all
Includes:
Analytics::Span, ForcedTracing::Span
Defined in:
lib/ddtrace/span.rb

Overview

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

Constant Summary collapse

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.

(1 << 62) - 1
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

1 << 64
NUMERIC_TAG_SIZE_RANGE =

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

(-1 << 53..1 << 53).freeze
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 Also:

{
  Ext::DistributedTracing::ORIGIN_KEY => true,
  Ext::Environment::TAG_VERSION => true,
  Ext::HTTP::STATUS_CODE => true,
  Ext::NET::TAG_HOSTNAME => true
}.freeze

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(tracer, name, options = {}) ⇒ Span

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. +nil+ can be used as a placeholder, when the resource value is not yet known at +#initialize+ time.
  • +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


75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
 
# File 'lib/ddtrace/span.rb', line 75

def initialize(tracer, name, options = {})
  @tracer = tracer

  @name = name
  @service = options.fetch(:service, nil)
  @resource = 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

Instance Attribute Details

#context ⇒ Object

Returns the value of attribute context.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def context
  @context
end

#duration ⇒ Object 



405
406
407
408
409
410
411
 
# File 'lib/ddtrace/span.rb', line 405

def duration
  if @duration_end.nil? || @duration_start.nil?
    @end_time - @start_time
  else
    @duration_end - @duration_start
  end
end

#end_time ⇒ Object

Returns the value of attribute end_time.



61
62
63
 
# File 'lib/ddtrace/span.rb', line 61

def end_time
  @end_time
end

#name ⇒ Object

Returns the value of attribute name.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def name
  @name
end

#parent ⇒ Object

Returns the value of attribute parent.



61
62
63
 
# File 'lib/ddtrace/span.rb', line 61

def parent
  @parent
end

#parent_id ⇒ Object

Returns the value of attribute parent_id.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def parent_id
  @parent_id
end

#resource ⇒ Object

Returns the value of attribute resource.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def resource
  @resource
end

#resource_container ⇒ Object (readonly)

Returns the value of attribute resource_container.



61
62
63
 
# File 'lib/ddtrace/span.rb', line 61

def resource_container
  @resource_container
end

#sampled ⇒ Object

Returns the value of attribute sampled.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def sampled
  @sampled
end

#service ⇒ Object

Returns the value of attribute service.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def service
  @service
end

#span_id ⇒ Object

Returns the value of attribute span_id.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def span_id
  @span_id
end

#span_type ⇒ Object

Returns the value of attribute span_type.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def span_type
  @span_type
end

#start_time ⇒ Object

Returns the value of attribute start_time.



61
62
63
 
# File 'lib/ddtrace/span.rb', line 61

def start_time
  @start_time
end

#status ⇒ Object

Returns the value of attribute status.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def status
  @status
end

#trace_id ⇒ Object

Returns the value of attribute trace_id.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def trace_id
  @trace_id
end

#tracer ⇒ Object

Returns the value of attribute tracer.



56
57
58
 
# File 'lib/ddtrace/span.rb', line 56

def tracer
  @tracer
end

Instance Method Details

#allocations ⇒ Object 



276
277
278
 
# File 'lib/ddtrace/span.rb', line 276

def allocations
  @allocation_count_finish - @allocation_count_start
end

#clear_metric(key) ⇒ Object

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



171
172
173
 
# File 'lib/ddtrace/span.rb', line 171

def clear_metric(key)
  @metrics.delete(key)
end

#clear_tag(key) ⇒ Object

This method removes a tag for the given key.



148
149
150
 
# File 'lib/ddtrace/span.rb', line 148

def clear_tag(key)
  @meta.delete(key)
end

#finish(finish_time = nil) ⇒ Object

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



213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
 
# File 'lib/ddtrace/span.rb', line 213

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? ⇒ Boolean

Return whether the duration is finished or not.

Returns:

  • (Boolean) 


401
402
403
 
# File 'lib/ddtrace/span.rb', line 401

def finished?
  !@end_time.nil?
end

#get_metric(key) ⇒ Object

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



176
177
178
 
# File 'lib/ddtrace/span.rb', line 176

def get_metric(key)
  @metrics[key] || @meta[key]
end

#get_tag(key) ⇒ Object

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



153
154
155
 
# File 'lib/ddtrace/span.rb', line 153

def get_tag(key)
  @meta[key] || @metrics[key]
end

#pretty_print(q) ⇒ Object

Return a human readable version of the span



363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
 
# File 'lib/ddtrace/span.rb', line 363

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

#set_error(e) ⇒ Object

Mark the span with the given error.



181
182
183
184
185
186
187
188
 
# File 'lib/ddtrace/span.rb', line 181

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) ⇒ Object

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.



159
160
161
162
163
164
165
166
167
168
 
# File 'lib/ddtrace/span.rb', line 159

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) ⇒ Object

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



256
257
258
 
# File 'lib/ddtrace/span.rb', line 256

def set_parent(parent)
  self.parent = parent
end

#set_tag(key, value = nil) ⇒ Object

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)



116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
 
# File 'lib/ddtrace/span.rb', line 116

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) ⇒ Object

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" })



143
144
145
 
# File 'lib/ddtrace/span.rb', line 143

def set_tags(tags)
  tags.each { |k, v| set_tag(k, v) }
end

#start(start_time = nil) ⇒ Object

Mark the span started at the current time.



191
192
193
194
195
196
197
198
199
200
 
# File 'lib/ddtrace/span.rb', line 191

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

#started? ⇒ Boolean

Return whether the duration is started or not

Returns:

  • (Boolean) 


396
397
398
 
# File 'lib/ddtrace/span.rb', line 396

def started?
  !@start_time.nil?
end

#to_hash ⇒ Object

Return the hash representation of the current span.



281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
 
# File 'lib/ddtrace/span.rb', line 281

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) ⇒ Object

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



358
359
360
 
# File 'lib/ddtrace/span.rb', line 358

def to_json(*args)
  to_hash.to_json(*args)
end

#to_msgpack(packer = nil) ⇒ Object

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.

Parameters:

  • packer (MessagePack::Packer) (defaults to: nil) —

    serialization buffer, can be +nil+ with JRuby



312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
 
# File 'lib/ddtrace/span.rb', line 312

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 ⇒ Object

Return a string representation of the span.



251
252
253
 
# File 'lib/ddtrace/span.rb', line 251

def to_s
  "Span(name:#{@name},sid:#{@span_id},tid:#{@trace_id},pid:#{@parent_id})"
end