Module: DeadBro::WatchTracker

Defined in:
lib/dead_bro/watch_tracker.rb

Overview

Records user-defined timed blocks (DeadBro.watch) during an instrumented request or background job. Spans include wall duration, nesting depth, and SQL attributable to the block (delta from SqlSubscriber aggregates).

SQL attribution: each span diffs the global SQL counter at block entry vs exit. Nested blocks each get their own diff; a parent span's sql_count / sql_duration_ms therefore includes queries run inside nested child spans (inclusive totals, not exclusive). Compare inner spans when you need per-block SQL; do not sum parent and child counts.

Unlike DeadBro.analyze, watch spans are sent to the DeadBro backend as part of the normal request/job payload when watch_enabled is on.

Constant Summary collapse

THREAD_LOCAL_EVENTS_KEY = 
:dead_bro_watch_events
THREAD_LOCAL_ACTIVE_STACK_KEY = 
:dead_bro_watch_active_stack
MAX_DEPTH =

Deepest depth index still recorded — depths 0..MAX_DEPTH are kept, anything nested below that yields untracked.

10
MAX_SPANS_PER_REQUEST = 
50
MAX_LABEL_LENGTH = 
200
MAX_TAGS = 
5
MAX_TAG_VALUE_LENGTH = 
100

Class Method Summary collapse

Class Method Details

.append_completed_span(events, frame) ⇒ Object 



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# File 'lib/dead_bro/watch_tracker.rb', line 151

def append_completed_span(events, frame)
  return unless events.is_a?(Array)

  slot = frame[:slot]
  return unless slot.is_a?(Integer) && slot < events.length

  elapsed_ms = begin
    ((Process.clock_gettime(Process::CLOCK_MONOTONIC) - frame[:block_start]) * 1000.0).round(2)
  rescue StandardError
    0.0
  end

  sql_after = sql_metrics_snapshot
  sql_before = frame[:sql_before] || {count: 0, duration_ms: 0.0}
  sql_count = [(sql_after[:count] || 0).to_i - (sql_before[:count] || 0).to_i, 0].max
  sql_duration_ms = [
    (sql_after[:duration_ms] || 0.0).to_f - (sql_before[:duration_ms] || 0.0).to_f,
    0.0
  ].max.round(2)

  span = {
    label: frame[:label],
    duration_ms: elapsed_ms,
    start_offset_ms: frame[:start_offset_ms],
    depth: frame[:depth],
    sql_count: sql_count,
    sql_duration_ms: sql_duration_ms,
    error: frame[:error] == true
  }
  span[:exception_class] = frame[:exception_class] if frame[:exception_class]
  tags = frame[:tags]
  span[:tags] = tags if tags.is_a?(Hash) && tags.any?

  events[slot] = span
rescue StandardError
  # Never raise from instrumentation
end

.compute_start_offset_ms ⇒ Object 



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# File 'lib/dead_bro/watch_tracker.rb', line 134

def compute_start_offset_ms
  tracking_start = Thread.current[DeadBro::TRACKING_START_TIME_KEY]
  return 0.0 unless tracking_start

  ((Time.now - tracking_start) * 1000.0).round(2)
rescue StandardError
  0.0
end

.enabled? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/dead_bro/watch_tracker.rb', line 30

def enabled?
  DeadBro.configuration.watch_enabled?
rescue StandardError
  false
end

.sanitize_label(label) ⇒ Object 



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# File 'lib/dead_bro/watch_tracker.rb', line 111

def sanitize_label(label)
  text = label.to_s.strip
  text = "block" if text.empty?
  (text.length > MAX_LABEL_LENGTH) ? text[0, MAX_LABEL_LENGTH] + "..." : text
rescue StandardError
  "block"
end

.sanitize_tags(tags) ⇒ Object 



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# File 'lib/dead_bro/watch_tracker.rb', line 119

def sanitize_tags(tags)
  return {} unless tags.is_a?(Hash) && tags.any?

  tags.first(MAX_TAGS).each_with_object({}) do |(key, value), out|
    k = key.to_s.strip[0, 50]
    next if k.empty?

    v = value.to_s.strip
    v = v[0, MAX_TAG_VALUE_LENGTH] + "..." if v.length > MAX_TAG_VALUE_LENGTH
    out[k] = v
  end
rescue StandardError
  {}
end

.sql_metrics_snapshot ⇒ Object 



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# File 'lib/dead_bro/watch_tracker.rb', line 143

def sql_metrics_snapshot
  return {count: 0, duration_ms: 0.0} unless defined?(DeadBro::SqlSubscriber)

  DeadBro::SqlSubscriber.current_sql_metrics
rescue StandardError
  {count: 0, duration_ms: 0.0}
end

.start_request_tracking ⇒ Object 



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# File 'lib/dead_bro/watch_tracker.rb', line 42

def start_request_tracking
  Thread.current[THREAD_LOCAL_EVENTS_KEY] = []
  Thread.current[THREAD_LOCAL_ACTIVE_STACK_KEY] = []
end

.stop_request_tracking ⇒ Object 



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# File 'lib/dead_bro/watch_tracker.rb', line 47

def stop_request_tracking
  events = Thread.current[THREAD_LOCAL_EVENTS_KEY]
  Thread.current[THREAD_LOCAL_EVENTS_KEY] = nil
  Thread.current[THREAD_LOCAL_ACTIVE_STACK_KEY] = nil
  # compact drops reserved slots whose block never completed — can't happen
  # for a lexical block, but keeps a nil out of the payload if it ever does.
  events.is_a?(Array) ? events.compact : []
rescue StandardError
  []
end

.tracking_active? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/dead_bro/watch_tracker.rb', line 36

def tracking_active?
  Thread.current[THREAD_LOCAL_EVENTS_KEY].is_a?(Array)
rescue StandardError
  false
end

.watch(label = nil, **tags) ⇒ Object 



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# File 'lib/dead_bro/watch_tracker.rb', line 58

def watch(label = nil, **tags)
  return yield unless block_given?
  return yield unless enabled?
  return yield unless tracking_active?

  events = Thread.current[THREAD_LOCAL_EVENTS_KEY]
  active_stack = Thread.current[THREAD_LOCAL_ACTIVE_STACK_KEY]
  return yield unless events.is_a?(Array) && active_stack.is_a?(Array)

  depth = active_stack.length
  return yield if depth > MAX_DEPTH
  return yield if events.length >= MAX_SPANS_PER_REQUEST

  sanitized_label = sanitize_label(label)
  sanitized_tags = sanitize_tags(tags)
  start_offset_ms = compute_start_offset_ms
  sql_before = sql_metrics_snapshot
  block_start = Process.clock_gettime(Process::CLOCK_MONOTONIC)

  frame = {
    label: sanitized_label,
    depth: depth,
    tags: sanitized_tags,
    start_offset_ms: start_offset_ms,
    sql_before: sql_before,
    block_start: block_start,
    error: false,
    exception_class: nil
  }
  # Reserve the slot on entry so spans come out in start order. Blocks only
  # complete inner-first, so appending on completion would emit a nested span
  # ahead of its own parent; the placeholder keeps parents before children.
  # It also makes MAX_SPANS_PER_REQUEST count blocks still in flight.
  frame[:slot] = events.length
  events << nil
  active_stack << frame

  begin
    yield
  rescue StandardError => e
    frame[:error] = true
    # Anonymous classes (Class.new(StandardError)) have a nil name — leave the
    # field unset rather than shipping an empty string the dashboard would
    # render as a blank exception.
    class_name = e.class.name
    frame[:exception_class] = class_name[0, 200] if class_name
    raise
  ensure
    active_stack.pop if active_stack.last.equal?(frame)
    append_completed_span(events, frame)
  end
end