Class: OpenTrace::Middleware

Inherits:
Object
  • Object
show all
Defined in:
lib/opentrace/middleware.rb

Constant Summary collapse

FIBER_KEYS =

All Fiber-local keys managed by this middleware. Centralised so cleanup never misses one.

%i[
  opentrace_collector
  opentrace_cached_context
  opentrace_sql_count
  opentrace_sql_total_ms
  opentrace_trace_id
  opentrace_span_id
  opentrace_parent_span_id
  opentrace_transaction_name
  opentrace_breadcrumbs
  opentrace_session_id
  opentrace_pending_explains
  opentrace_buffer
  opentrace_buffer_allocation_bytes
].freeze

Instance Method Summary collapse

Constructor Details

#initialize(app) ⇒ Middleware

Returns a new instance of Middleware.



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# File 'lib/opentrace/middleware.rb', line 27

def initialize(app)
  @app = app
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/opentrace/middleware.rb', line 31

def call(env)
  # When OpenTrace is disabled, pass through with zero overhead
  return @app.call(env) unless OpenTrace.enabled?
  return @app.call(env) if ignored_path?(env["PATH_INFO"])

  # Sampling: skip ALL Fiber-local setup for unsampled requests.
  # Subscribers check Fiber-locals and return instantly when nil.
  unless OpenTrace.sampler.sample?(env)
    OpenTrace.send(:client).stats.increment(:sampled_out)
    return @app.call(env)
  end

  request_id = env["action_dispatch.request_id"] || env["HTTP_X_REQUEST_ID"]
  OpenTrace.current_request_id = request_id
  Fiber[:opentrace_sql_count] = 0
  Fiber[:opentrace_sql_total_ms] = 0.0

  # Extract or generate trace context
  if OpenTrace.config.trace_propagation
    trace_id, parent_span_id = extract_trace_context(env)
    span_id = TraceContext.generate_span_id

    Fiber[:opentrace_trace_id] = trace_id
    Fiber[:opentrace_span_id] = span_id
    Fiber[:opentrace_parent_span_id] = parent_span_id
  end

  # Session tracking (opt-in)
  if OpenTrace.config.session_tracking
    session_id = extract_session_id(env)
    Fiber[:opentrace_session_id] = session_id if session_id
  end

  # Create RequestCollector only when features that need it are enabled
  cfg = OpenTrace.config
  needs_collector = cfg.request_summary &&
    (cfg.view_tracking || cfg.cache_tracking || cfg.http_tracking ||
     cfg.timeline || cfg.memory_tracking)

  if needs_collector
    max_timeline = cfg.timeline ? cfg.timeline_max_events : 0
    collector = OpenTrace::RequestCollector.new(max_timeline: max_timeline)
    Fiber[:opentrace_collector] = collector

    if cfg.memory_tracking
      collector.memory_before = current_rss_mb
    end
  end

  # ── Deep capture: set up InstrumentationContext ──
  buffer = setup_buffer(env, cfg) if request_capture_enabled?(cfg)

  # ── Call the downstream app ──
  start_time = Process.clock_gettime(Process::CLOCK_MONOTONIC)
  had_error = false

  status, headers, body = @app.call(env)

  # ── Capture response data into the buffer ──
  capture_response(buffer, status, headers, body) if buffer

  [status, headers, body]
rescue StandardError => e
  had_error = true
  raise
ensure
  # Calculate duration
  duration_ms = if start_time
                  ((Process.clock_gettime(Process::CLOCK_MONOTONIC) - start_time) * 1000).round(2)
                end

  # Memory snapshot after request (opt-in)
  collector = Fiber[:opentrace_collector]
  if collector && OpenTrace.config.memory_tracking && collector.memory_before
    collector.memory_after = current_rss_mb
  end

  # ── Deep capture: teardown and enqueue ──
  begin
    if Fiber[:opentrace_buffer]
      doc = InstrumentationContext.teardown(
        status: status,
        duration_ms: duration_ms,
        error: had_error
      )
      OpenTrace.client_enqueue_raw(doc) if doc
    end
  rescue StandardError
    # Never affect the host app
  end

  cleanup_fiber_locals
  OpenTrace.current_request_id = nil
end