Module: MetrixWire::Instrument::Helpers

Defined in:
lib/metrixwire/instrument/helpers.rb

Overview

Shared helpers used by every low-level patch (PG, mysql2, Net::HTTP, …). These attach spans to the current trace only; if there's no active trace (work outside a request), they no-op. Never throw.

Class Method Summary collapse

Class Method Details

.add_span(type, description, duration_ms, meta: nil, source_location: :auto) ⇒ Object

Add a span to the active trace. duration_ms is a float; description is e.g. the SQL text or "GET https://host/path".



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# File 'lib/metrixwire/instrument/helpers.rb', line 13

def add_span(type, description, duration_ms, meta: nil, source_location: :auto)
  trace = Context.current
  return if trace.nil? || description.nil? || description.to_s.empty?

  loc = source_location == :auto ? SourceLocation.nearest : source_location
  span = Span.new(
    type: type,
    description: description.to_s,
    started_at: MetrixWire.iso8601(Time.now - (duration_ms / 1000.0)),
    duration_ms: [duration_ms, 0].max.round,
    source_location: loc,
    meta: (meta && !meta.empty? ? meta : nil)
  )
  trace.add_span(span)
rescue StandardError
  # instrumentation must never throw
end

.db_query(sql) ⇒ Object

Time a block, then record a db_query span. Returns the block's result.



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# File 'lib/metrixwire/instrument/helpers.rb', line 32

def db_query(sql)
  return yield if Context.current.nil?

  t0 = MetrixWire.monotonic_ms
  result = yield
  add_span("db_query", sql, MetrixWire.monotonic_ms - t0, meta: row_count_meta(result))
  result
rescue StandardError
  raise
end

.extract_row_count(result) ⇒ Object

Best-effort row count across PG::Result / Mysql2::Result / Array / etc.



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# File 'lib/metrixwire/instrument/helpers.rb', line 51

def extract_row_count(result)
  if result.respond_to?(:cmd_tuples) && result.respond_to?(:ntuples)
    # PG::Result: prefer affected rows for writes, tuple count for reads.
    nt = result.ntuples
    return nt if nt && nt > 0

    ct = result.cmd_tuples
    return ct if ct && ct >= 0

    nt
  elsif result.respond_to?(:count) && !result.is_a?(String)
    result.count
  elsif result.respond_to?(:size)
    result.size
  end
rescue StandardError
  nil
end

.row_count_meta(result) ⇒ Object 



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# File 'lib/metrixwire/instrument/helpers.rb', line 43

def row_count_meta(result)
  n = extract_row_count(result)
  n.nil? ? nil : { rowCount: n }
rescue StandardError
  nil
end