Class: OpenTelemetry::Instrumentation::Rack::Middlewares::TracerMiddleware

Inherits:
Object
  • Object
show all
Defined in:
lib/opentelemetry/instrumentation/rack/middlewares/tracer_middleware.rb

Overview

TracerMiddleware propagates context and instruments Rack requests by way of its middleware system

Constant Summary collapse

EMPTY_HASH = 
{}.freeze

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(app) ⇒ TracerMiddleware

Returns a new instance of TracerMiddleware.



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# File 'lib/opentelemetry/instrumentation/rack/middlewares/tracer_middleware.rb', line 54

def initialize(app)
  @app = app
  @untraced_endpoints = config[:untraced_endpoints]
end

Class Method Details

.allowed_rack_request_headers ⇒ Object 



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# File 'lib/opentelemetry/instrumentation/rack/middlewares/tracer_middleware.rb', line 17

def allowed_rack_request_headers
  @allowed_rack_request_headers ||= Array(config[:allowed_request_headers]).each_with_object({}) do |header, memo|
    key = header.to_s.upcase.gsub(/[-\s]/, '_')
    case key
    when 'CONTENT_TYPE', 'CONTENT_LENGTH'
      memo[key] = build_attribute_name('http.request.header.', header)
    else
      memo["HTTP_#{key}"] = build_attribute_name('http.request.header.', header)
    end
  end
end

.allowed_response_headers ⇒ Object 



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# File 'lib/opentelemetry/instrumentation/rack/middlewares/tracer_middleware.rb', line 29

def allowed_response_headers
  @allowed_response_headers ||= Array(config[:allowed_response_headers]).each_with_object({}) do |header, memo|
    memo[header] = build_attribute_name('http.response.header.', header)
    memo[header.to_s.upcase] = build_attribute_name('http.response.header.', header)
  end
end

.build_attribute_name(prefix, suffix) ⇒ Object 



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# File 'lib/opentelemetry/instrumentation/rack/middlewares/tracer_middleware.rb', line 36

def build_attribute_name(prefix, suffix)
  prefix + suffix.to_s.downcase.gsub(/[-\s]/, '_')
end

.config ⇒ Object 



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# File 'lib/opentelemetry/instrumentation/rack/middlewares/tracer_middleware.rb', line 40

def config
  Rack::Instrumentation.instance.config
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/opentelemetry/instrumentation/rack/middlewares/tracer_middleware.rb', line 59

def call(env)
  if untraced_request?(env)
    OpenTelemetry::Common::Utilities.untraced do
      return @app.call(env)
    end
  end

  original_env = env.dup
  extracted_context = OpenTelemetry.propagation.extract(
    env,
    getter: OpenTelemetry::Common::Propagation.rack_env_getter
  )
  frontend_context = create_frontend_span(env, extracted_context)

  # restore extracted context in this process:
  OpenTelemetry::Context.with_current(frontend_context || extracted_context) do
    request_span_name = create_request_span_name(env['REQUEST_URI'] || original_env['PATH_INFO'], env)
    request_span_kind = frontend_context.nil? ? :server : :internal
    tracer.in_span(request_span_name,
                   attributes: request_span_attributes(env: env),
                   kind: request_span_kind) do |request_span|
      OpenTelemetry::Instrumentation::Rack.with_span(request_span) do
        @app.call(env).tap do |status, headers, response|
          set_attributes_after_request(request_span, status, headers, response)
          config[:response_propagators].each { |propagator| propagator.inject(headers) }
        end
      end
    end
  end
ensure
  finish_span(frontend_context)
end