Class: XRay::Rack::Middleware

Inherits:
Object
  • Object
show all
Includes:
Facets::Helper
Defined in:
lib/aws-xray-sdk/facets/rack.rb

Overview

Rack middleware that generates a segment for each request/response cycle.

Constant Summary collapse

X_FORWARD = 
'HTTP_X_FORWARDED_FOR'.freeze
SCHEME_SEPARATOR = 
"://".freeze

Constants included from Facets::Helper

Facets::Helper::TRACE_HEADER, Facets::Helper::TRACE_HEADER_PROXY

Instance Method Summary collapse

Methods included from Facets::Helper

#construct_header, #prep_header_str, #should_sample?

Constructor Details

#initialize(app, recorder: nil) ⇒ Middleware

Returns a new instance of Middleware.



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# File 'lib/aws-xray-sdk/facets/rack.rb', line 13

def initialize(app, recorder: nil)
  @app = app
  @recorder = recorder || XRay.recorder
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/aws-xray-sdk/facets/rack.rb', line 18

def call(env)
  header = construct_header(headers: env)
  req = ::Rack::Request.new(env)

  # params required for path based sampling
  host = req.host
  url_path = req.path
  method = req.request_method
  # get segment name from host header if applicable
  seg_name = @recorder.segment_naming.provide_name(host: req.host)

  # get sampling decision
  sampled = should_sample?(
    header_obj: header, recorder: @recorder, sampling_req:
    { host: host, http_method: method, url_path: url_path, service: seg_name }
  )

  # begin the segment
  segment = @recorder.begin_segment seg_name, trace_id: header.root, parent_id: header.parent_id,
                                              sampled: sampled

  # add neccessary http request metadata to the segment
  req_meta = extract_request_meta(req)
  segment.merge_http_request request: req_meta unless req_meta.empty?
  begin
    status, headers, body = @app.call env
    resp_meta = {}
    resp_meta[:status] = status
    # Don't set content_length if it is not available on headers.
    resp_obj = ::Rack::Response.new body: body, status: status, headers: headers
    if len = resp_obj.content_length
      resp_meta[:content_length] = len
    end
    segment.merge_http_response response: resp_meta
    trace_header = {TRACE_HEADER => TraceHeader.from_entity(entity: segment).root_string}
    headers.merge!(trace_header)
    [status, headers, body]
  rescue Exception => e
    segment.apply_status_code status: 500
    segment.add_exception exception: e
    raise e
  ensure
    @recorder.end_segment
  end
end