Class: NewRelic::Agent::TransactionSampler

Inherits:
Object
  • Object
show all
Defined in:
lib/new_relic/agent/transaction_sampler.rb

Overview

This class contains the logic of sampling a transaction - creation and modification of transaction samples

Defined Under Namespace

Modules: Shim

Constant Summary collapse

BUILDER_KEY = 
:transaction_sample_builder
MAX_DATA_LENGTH = 
16384

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ TransactionSampler

Returns a new instance of TransactionSampler.



31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 31

def initialize

  # @samples is an array of recent samples up to @max_samples in
  # size - it's only used by developer mode
  @samples = []
  @force_persist = []
  @max_samples = 100

  # @harvest_count is a count of harvests used for random
  # sampling - we pull 1 @random_sample in every @sampling_rate harvests
  @harvest_count = 0
  @random_sample = nil
  @sampling_rate = Agent.config[:sample_rate]

  # This lock is used to synchronize access to the @last_sample
  # and related variables. It can become necessary on JRuby or
  # any 'honest-to-god'-multithreaded system
  @samples_lock = Mutex.new

  Agent.config.register_callback(:'transaction_tracer.enabled') do |enabled|
    if enabled
      threshold = Agent.config[:'transaction_tracer.transaction_threshold']
      ::NewRelic::Agent.logger.debug "Transaction tracing threshold is #{threshold} seconds."
    else
      ::NewRelic::Agent.logger.debug "Transaction traces will not be sent to the New Relic service."
    end
  end

  Agent.config.register_callback(:'transaction_tracer.record_sql') do |config|
    if config == 'raw'
      ::NewRelic::Agent.logger.warn("Agent is configured to send raw SQL to the service")
    end
  end
end

Instance Attribute Details

#disabled ⇒ Object (readonly)

Returns the value of attribute disabled.



29
30
31
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 29

def disabled
  @disabled
end

#last_sample ⇒ Object (readonly)

Returns the value of attribute last_sample.



29
30
31
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 29

def last_sample
  @last_sample
end

#random_sampling ⇒ Object

Returns the value of attribute random_sampling.



27
28
29
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 27

def random_sampling
  @random_sampling
end

#samples ⇒ Object (readonly)

Returns the value of attribute samples.



29
30
31
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 29

def samples
  @samples
end

#sampling_rate ⇒ Object

Returns the value of attribute sampling_rate.



27
28
29
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 27

def sampling_rate
  @sampling_rate
end

#slow_capture_threshold ⇒ Object

Returns the value of attribute slow_capture_threshold.



28
29
30
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 28

def slow_capture_threshold
  @slow_capture_threshold
end

Class Method Details

.truncate_message(message) ⇒ Object

Truncates the message to ‘MAX_DATA_LENGTH` if needed, and appends an ellipsis because it makes the trucation clearer in the UI



283
284
285
286
287
288
289
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 283

def self.truncate_message(message)
  if message.length > (MAX_DATA_LENGTH - 4)
    message[0..MAX_DATA_LENGTH - 4] + '...'
  else
    message
  end
end

Instance Method Details

#add_force_persist_to(result) ⇒ Object 



366
367
368
369
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 366

def add_force_persist_to(result)
  result.concat(@force_persist)
  @force_persist = []
end

#add_random_sample_to(result) ⇒ Object

Every 1/n harvests, adds the most recent sample to the harvest array if it exists. Makes sure that the random sample is not also the slowest sample for this harvest by ‘uniq!`ing the result array

random sampling is very, very seldom used



355
356
357
358
359
360
361
362
363
364
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 355

def add_random_sample_to(result)
  return unless @random_sample &&
    Agent.config[:sample_rate] && Agent.config[:sample_rate].to_i > 0
  @harvest_count += 1
  if (@harvest_count.to_i % Agent.config[:sample_rate].to_i) == 0
    result << @random_sample if @random_sample
    @harvest_count = 0
  end
  nil # don't assume this method returns anything
end

#add_samples_to(result) ⇒ Object

Returns an array of slow samples, with either one or two elements - one element unless random sampling is enabled. The sample returned will be the slowest sample among those available during this harvest



375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 375

def add_samples_to(result)
  # pull out force persist
  force_persist = result.select {|sample| sample.force_persist} || []
  result.reject! {|sample| sample.force_persist}

  force_persist.each {|sample| store_force_persist(sample)}

  result << @slowest_sample if @slowest_sample

  result.compact!
  result = result.sort_by { |x| x.duration }
  result = result[-1..-1] || []               # take the slowest sample

  add_random_sample_to(result)
  add_force_persist_to(result)

  result.uniq
end

#add_segment_parameters(params) ⇒ Object

Set parameters on the current segment.



344
345
346
347
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 344

def add_segment_parameters( params )
  return unless builder
  builder.current_segment.params.merge!( params )
end

#append_backtrace(segment, duration) ⇒ Object

Appends a backtrace to a segment if that segment took longer than the specified duration



303
304
305
306
307
308
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 303

def append_backtrace(segment, duration)
  if (duration >= Agent.config[:'transaction_tracer.stack_trace_threshold'] ||
      Thread.current[:capture_deep_tt])
    segment[:backtrace] = caller.join("\n")
  end
end

#append_new_message(old_message, message) ⇒ Object

Allows the addition of multiple pieces of metadata to one segment - i.e. traced method calls multiple sql queries



293
294
295
296
297
298
299
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 293

def append_new_message(old_message, message)
  if old_message
    old_message + ";\n" + message
  else
    message
  end
end

#build_database_statement(sql, config, explainer) ⇒ Object 



321
322
323
324
325
326
327
328
329
330
331
332
333
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 321

def build_database_statement(sql, config, explainer)
  statement = Database::Statement.new(self.class.truncate_message(sql))
  if config
    statement.adapter = config[:adapter]
    statement.config = config
  end
  if Agent.config[:override_sql_obfuscation_adapter]
    statement.adapter = Agent.config[:override_sql_obfuscation_adapter]
  end
  statement.explainer = explainer

  statement
end

#builder ⇒ Object

The current thread-local transaction sample builder



456
457
458
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 456

def builder
  Thread::current[BUILDER_KEY]
end

#capture_segment_trace ⇒ Object

in developer mode, capture the stack trace with the segment. this is cpu and memory expensive and therefore should not be turned on in production mode



111
112
113
114
115
116
117
118
119
120
121
122
123
124
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 111

def capture_segment_trace
  return unless Agent.config[:developer_mode]
  segment = builder.current_segment
  if segment
    # Strip stack frames off the top that match /new_relic/agent/
    trace = caller
    while trace.first =~/\/lib\/new_relic\/agent\//
      trace.shift
    end

    trace = trace[0..39] if trace.length > 40
    segment[:backtrace] = trace
  end
end

#clamp_number_tts(tts, limit) ⇒ Object

JON - THIS CODE NEEDS A UNIT TEST



417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 417

def clamp_number_tts(tts, limit)
  tts.sort! do |a,b|
    if a.force_persist && b.force_persist
      b.duration <=> a.duration
    elsif a.force_persist
      -1
    elsif b.force_persist
      1
    else
      b.duration <=> a.duration
    end
  end

  tts[0..(limit-1)]
end

#clear_builder ⇒ Object

Sets the thread local variable storing the transaction sample builder to nil to clear it



462
463
464
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 462

def clear_builder
  Thread::current[BUILDER_KEY] = nil
end

#current_sample_id ⇒ Object

Returns the current sample id, delegated from ‘builder`



67
68
69
70
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 67

def current_sample_id
  b=builder
  b and b.sample_id
end

#enabled? ⇒ Boolean

Returns:

  • (Boolean) 


72
73
74
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 72

def enabled?
  Agent.config[:'transaction_tracer.enabled'] || Agent.config[:developer_mode]
end

#harvest(previous = []) ⇒ Object

get the set of collected samples, merging into previous samples, and clear the collected sample list. Truncates samples to a specified segment_limit to save memory and bandwith transmitting samples to the server.



398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 398

def harvest(previous=[])
  return [] if !enabled?
  result = Array(previous)

  @samples_lock.synchronize do
    result = add_samples_to(result)

    # clear previous transaction samples
    @slowest_sample = nil
    @random_sample = nil
    @last_sample = nil
  end

  # Clamp the number of TTs we'll keep in memory and send
  result = clamp_number_tts(result, 20) if result.length > 20
  result
end

#ignore_transaction ⇒ Object

Tells the builder to ignore a transaction, if we are currently creating one. Only causes the sample to be ignored upon end of the transaction, and does not change the metrics gathered outside of the sampler



245
246
247
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 245

def ignore_transaction
  builder.ignore_transaction if builder
end

#notice_first_scope_push(time) ⇒ Object

Creates a new transaction sample builder, unless the transaction sampler is disabled. Takes a time parameter for the start of the transaction sample



88
89
90
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 88

def notice_first_scope_push(time)
  start_builder(time.to_f) if enabled?
end

#notice_nosql(key, duration) ⇒ Object

Adds non-sql metadata to a segment - generally the memcached key

duration is seconds, float value.



339
340
341
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 339

def notice_nosql(key, duration)
  notice_extra_data(key, duration, :key)
end

#notice_pop_scope(scope, time = Time.now) ⇒ Object

Informs the transaction sample builder about the end of a traced scope



136
137
138
139
140
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 136

def notice_pop_scope(scope, time = Time.now)
  return unless builder
  raise "frozen already???" if builder.sample.frozen?
  builder.trace_exit(scope, time.to_f)
end

#notice_profile(profile) ⇒ Object

For developer mode profiling support - delegates to the builder



250
251
252
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 250

def notice_profile(profile)
  builder.set_profile(profile) if builder
end

#notice_push_scope(time = Time.now) ⇒ Object

This delegates to the builder to create a new open transaction segment for the specified scope, beginning at the optionally specified time.

Note that in developer mode, this captures a stacktrace for the beginning of each segment, which can be fairly slow



98
99
100
101
102
103
104
105
106
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 98

def notice_push_scope(time=Time.now)
  return unless builder

  segment = builder.trace_entry(time.to_f)

  capture_segment_trace if Agent.config[:developer_mode]

  return segment
end

#notice_scope_empty(txn, time = Time.now, gc_time = nil) ⇒ Object

This is called when we are done with the transaction. We’ve unwound the stack to the top level. It also clears the transaction sample builder so that it won’t continue to have scopes appended to it.

It sets various instance variables to the finished sample, depending on which settings are active. See ‘store_sample`



149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 149

def notice_scope_empty(txn, time=Time.now, gc_time=nil)
  last_builder = builder
  last_builder.set_transaction_name(txn.name) if enabled? && last_builder

  return unless last_builder

  last_builder.finish_trace(time.to_f, txn.custom_parameters)
  clear_builder
  return if last_builder.ignored?

  @samples_lock.synchronize do
    @last_sample = last_builder.sample
    @last_sample.set_custom_param(:gc_time, gc_time) if gc_time
    store_sample(@last_sample)
  end
end

#notice_sql(sql, config, duration, &explainer) ⇒ Object

some statements (particularly INSERTS with large BLOBS may be very large; we should trim them to a maximum usable length config is the driver configuration for the connection duration is seconds, float value.



314
315
316
317
318
319
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 314

def notice_sql(sql, config, duration, &explainer)
  if NewRelic::Agent.is_sql_recorded?
    statement = build_database_statement(sql, config, explainer)
    notice_extra_data(statement, duration, :sql)
  end
end

#notice_transaction(uri = nil, params = {}) ⇒ Object

Delegates to the builder to store the uri, and parameters if the sampler is active



237
238
239
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 237

def notice_transaction(uri=nil, params={})
  builder.set_transaction_info(uri, params) if enabled? && builder
end

#notice_transaction_cpu_time(cpu_time) ⇒ Object

Sets the CPU time used by a transaction, delegates to the builder



255
256
257
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 255

def notice_transaction_cpu_time(cpu_time)
  builder.set_transaction_cpu_time(cpu_time) if builder
end

#reset! ⇒ Object

reset samples without rebooting the web server



434
435
436
437
438
439
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 434

def reset!
  @samples = []
  @last_sample = nil
  @random_sample = nil
  @slowest_sample = nil
end

#scope_depth ⇒ Object

Defaults to zero, otherwise delegated to the transaction sample builder



128
129
130
131
132
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 128

def scope_depth
  return 0 unless builder

  builder.scope_depth
end

#slowest_sample?(old_sample, new_sample) ⇒ Boolean

Checks to see if the old sample exists, or if its duration is less than the new sample

Returns:

  • (Boolean) 


223
224
225
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 223

def slowest_sample?(old_sample, new_sample)
  old_sample.nil? || (new_sample.duration > old_sample.duration)
end

#start_builder(time = nil) ⇒ Object

Checks to see if the transaction sampler is disabled, if transaction trace recording is disabled by a thread local, or if execution is untraced - if so it clears the transaction sample builder from the thread local, otherwise it generates a new transaction sample builder with the stated time as a starting point and saves it in the thread local variable



447
448
449
450
451
452
453
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 447

def start_builder(time=nil)
  if !enabled? || !NewRelic::Agent.is_transaction_traced? || !NewRelic::Agent.is_execution_traced?
    clear_builder
  else
    Thread::current[BUILDER_KEY] ||= TransactionSampleBuilder.new(time)
  end
end

#store_force_persist(sample) ⇒ Object 



193
194
195
196
197
198
199
200
201
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 193

def store_force_persist(sample)
  @force_persist << sample

  # WARNING - this clamp should be configurable
  if @force_persist.length > 15
    @force_persist.sort! {|a,b| b.duration <=> a.duration}
    @force_persist = @force_persist[0..14]
  end
end

#store_random_sample(sample) ⇒ Object

Only active when random sampling is true - this is very rarely used. Always store the most recent sample so that random sampling can pick a few of the samples to store, upon harvest



189
190
191
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 189

def store_random_sample(sample)
  @random_sample = sample if Agent.config[:'transaction_tracer.random_sample']
end

#store_sample(sample) ⇒ Object

Samples can be stored in three places: the random sample variable, when random sampling is active, the developer mode slower than the current occupant of that slot



170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 170

def store_sample(sample)
  sampler_methods = [ :store_slowest_sample ]
  if Agent.config[:developer_mode]
    sampler_methods << :store_sample_for_developer_mode
  end
  if Agent.config[:'transaction_tracer.random_sample']
    sampler_methods << :store_random_sample
  end

  sampler_methods.each{|sym| send(sym, sample) }

  if NewRelic::Agent::TransactionInfo.get.force_persist_sample?(sample)
    store_force_persist(sample)
  end
end

#store_sample_for_developer_mode(sample) ⇒ Object

Samples take up a ton of memory, so we only store a lot of them in developer mode - we truncate to @max_samples



205
206
207
208
209
210
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 205

def store_sample_for_developer_mode(sample)
  return unless Agent.config[:developer_mode]
  @samples = [] unless @samples
  @samples << sample
  truncate_samples
end

#store_slowest_sample(sample) ⇒ Object

Sets @slowest_sample to the passed in sample if it is slower than the current sample in @slowest_sample



214
215
216
217
218
219
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 214

def store_slowest_sample(sample)
  if slowest_sample?(@slowest_sample, sample) && sample.threshold &&
      sample.duration >= sample.threshold
    @slowest_sample = sample
  end
end

#truncate_samples ⇒ Object

Smashes the @samples array down to the length of @max_samples by taking the last @max_samples elements of the array



229
230
231
232
233
 
# File 'lib/new_relic/agent/transaction_sampler.rb', line 229

def truncate_samples
  if @samples.length > @max_samples
    @samples = @samples[-@max_samples..-1]
  end
end