class Instana::Rack

Public Class Methods

new(app) click to toggle source
# File lib/instana/instrumentation/rack.rb, line 9
def initialize(app)
  @app = app
end

Public Instance Methods

call(env) click to toggle source
# File lib/instana/instrumentation/rack.rb, line 13
def call(env)
  req = InstrumentedRequest.new(env)
  kvs = {
    http: req.request_tags,
    service: ENV['INSTANA_SERVICE_NAME']
  }.reject { |_, v| v.nil? }

  current_span = ::Instana.tracer.log_start_or_continue(:rack, {}, req.incoming_context)

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

  if ::Instana.tracer.tracing?
    unless req.correlation_data.empty?
      current_span[:crid] = req.correlation_data[:id]
      current_span[:crtp] = req.correlation_data[:type]
    end

    if !req.instana_ancestor.empty? && req.continuing_from_trace_parent?
      current_span[:ia] = req.instana_ancestor
    end

    if req.continuing_from_trace_parent?
      current_span[:tp] = true
    end

    if req.external_trace_id?
      current_span[:lt] = req.external_trace_id
    end

    if req.synthetic?
      current_span[:sy] = true
    end

    # In case some previous middleware returned a string status, make sure that we're dealing with
    # an integer.  In Ruby nil.to_i, "asdfasdf".to_i will always return 0 from Ruby versions 1.8.7 and newer.
    # So if an 0 status is reported here, it indicates some other issue (e.g. no status from previous middleware)
    # See Rack Spec: https://www.rubydoc.info/github/rack/rack/file/SPEC#label-The+Status
    kvs[:http][:status] = status.to_i

    if status.to_i.between?(500, 511)
      # Because of the 5xx response, we flag this span as errored but
      # without a backtrace (no exception)
      ::Instana.tracer.log_error(nil)
    end

    # If the framework instrumentation provides a path template,
    # pass it into the span here.
    # See: https://www.instana.com/docs/tracing/custom-best-practices/#path-templates-visual-grouping-of-http-endpoints
    kvs[:http][:path_tpl] = env['INSTANA_HTTP_PATH_TEMPLATE'] if env['INSTANA_HTTP_PATH_TEMPLATE']

    # Save the span context before the trace ends so we can place
    # them in the response headers in the ensure block
    trace_context = ::Instana.tracer.current_span.context
  end

  [status, headers, response]
rescue Exception => e
  ::Instana.tracer.log_error(e) if ::Instana.tracer.tracing?
  raise
ensure
  if ::Instana.tracer.tracing?
    if headers
      # Set response headers; encode as hex string
      if trace_context.active?
        headers['X-Instana-T'] = trace_context.trace_id_header
        headers['X-Instana-S'] = trace_context.span_id_header
        headers['X-Instana-L'] = '1'

        headers['Tracestate'] = trace_context.trace_state_header
      else
        headers['X-Instana-L'] = '0'
      end

      headers['Traceparent'] = trace_context.trace_parent_header
      headers['Server-Timing'] = "intid;desc=#{trace_context.trace_id_header}"
    end

    ::Instana.tracer.log_end(:rack, kvs)
  end
end