Class: Rack::Tracer

Inherits:
Object
  • Object
show all
Defined in:
lib/rack/tracer.rb

Constant Summary collapse

REQUEST_URI = 
'REQUEST_URI'.freeze
REQUEST_METHOD = 
'REQUEST_METHOD'.freeze

Instance Method Summary collapse

Constructor Details

#initialize(app, tracer: OpenTracing.global_tracer, on_start_span: nil, on_finish_span: nil, trust_incoming_span: true, errors: [StandardError]) ⇒ Tracer

Create a new Rack Tracer middleware.

Parameters:

  • app —

    The Rack application/middlewares stack.

  • tracer (OpenTracing::Tracer) (defaults to: OpenTracing.global_tracer) —

    A tracer to be used when start_span, and extract is called.

  • on_start_span (Proc, nil) (defaults to: nil) —

    A callback evaluated after a new span is created.

  • on_finish_span (Proc, nil) (defaults to: nil) —

    A callback evaluated after a span is finished.

  • errors (Array<Class>) (defaults to: [StandardError]) —

    An array of error classes to be captured by the tracer as errors. Errors are not muted by the middleware, they’re re-raised afterwards.



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# File 'lib/rack/tracer.rb', line 19

def initialize(app, # rubocop:disable Metrics/ParameterLists
               tracer: OpenTracing.global_tracer,
               on_start_span: nil,
               on_finish_span: nil,
               trust_incoming_span: true,
               errors: [StandardError])
  @app = app
  @tracer = tracer
  @on_start_span = on_start_span
  @on_finish_span = on_finish_span
  @trust_incoming_span = trust_incoming_span
  @errors = errors
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/rack/tracer.rb', line 33

def call(env)
  method = env[REQUEST_METHOD]

  context = @tracer.extract(OpenTracing::FORMAT_RACK, env) if @trust_incoming_span
  scope = @tracer.start_active_span(
    method,
    child_of: context,
    tags: {
      'component' => 'rack',
      'span.kind' => 'server',
      'http.method' => method,
      'http.url' => env[REQUEST_URI]
    }
  )
  span = scope.span

  @on_start_span.call(span) if @on_start_span

  env['rack.span'] = span

  @app.call(env).tap do |status_code, _headers, _body|
    span.set_tag('http.status_code', status_code)

    route = route_from_env(env)
    span.operation_name = route if route
  end
rescue *@errors => e
  route = route_from_env(env)
  span.operation_name = route if route
  span.record_exception(e)
  raise
ensure
  begin
    scope.close
  ensure
    @on_finish_span.call(span) if @on_finish_span
  end
end