Class: TraceView::Rack

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

Overview

TraceView::Rack

The TraceView::Rack middleware used to sample a subset of incoming requests for instrumentation and reporting. Tracing context can be received here (via the X-Trace HTTP header) or initiated here based on configured tracing mode.

After the rack layer passes on to the following layers (Rails, Sinatra, Padrino, Grape), then the instrumentation downstream will automatically detect whether this is a sampled request or not and act accordingly. (to instrument or not)

Direct Known Subclasses

Oboe::Rack

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(app) ⇒ Rack

Returns a new instance of Rack.



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# File 'lib/traceview/inst/rack.rb', line 24

def initialize(app)
  @app = app
end

Instance Attribute Details

#app ⇒ Object (readonly)

Returns the value of attribute app.



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# File 'lib/traceview/inst/rack.rb', line 22

def app
  @app
end

Instance Method Details

#call(env) ⇒ Object 



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# File 'lib/traceview/inst/rack.rb', line 63

def call(env)
  rack_skipped = false

  # In the case of nested Ruby apps such as Grape inside of Rails
  # or Grape inside of Grape, each app has it's own instance
  # of rack middleware.  We avoid tracing rack more than once and
  # instead start instrumenting from the first rack pass.

  # If we're already tracing a rack layer, dont't start another one.
  if TraceView.tracing? && TraceView.layer == :rack
    rack_skipped = true
    TraceView.logger.debug "[traceview/rack] Rack skipped!"
    return @app.call(env)
  end

  req = ::Rack::Request.new(env)
  report_kvs = {}

  if TraceView::Config[:rack][:log_args]
    report_kvs[:URL] = ::CGI.unescape(req.fullpath)
  else
    report_kvs[:URL] = ::CGI.unescape(req.path)
  end

  # Detect and log AVW headers for sampling analysis
  report_kvs['X-TV-Meta'] = env['HTTP_X_TV_META'] if env.key?('HTTP_X_TV_META')

  # Check for and validate X-Trace request header to pick up tracing context
  xtrace = env.is_a?(Hash) ? env['HTTP_X_TRACE'] : nil
  xtrace_header = xtrace if xtrace && TraceView::XTrace.valid?(xtrace)

  # Under JRuby, JTraceView may have already started a trace.  Make note of this
  # if so and don't clear context on log_end (see traceview/api/logging.rb)
  TraceView.has_incoming_context = TraceView.tracing?
  TraceView.has_xtrace_header = xtrace_header
  TraceView.is_continued_trace = TraceView.has_incoming_context || TraceView.has_xtrace_header

  TraceView::API.log_start(:rack, xtrace_header, report_kvs)

  # We only trace a subset of requests based off of sample rate so if
  # TraceView::API.log_start really did start a trace, we act accordingly here.
  if TraceView.tracing?
    report_kvs = collect(req, env)

    # We log an info event with the HTTP KVs found in TraceView::Rack.collect
    # This is done here so in the case of stacks that try/catch/abort
    # (looking at you Grape) we're sure the KVs get reported now as
    # this code may not be returned to later.
    TraceView::API.log_info(:rack, report_kvs)

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

    xtrace = TraceView::API.log_end(:rack, :Status => status)
  else
    status, headers, response = @app.call(env)
  end

  [status, headers, response]
rescue Exception => e
  unless rack_skipped
    TraceView::API.log_exception(:rack, e)
    xtrace = TraceView::API.log_end(:rack, :Status => 500)
  end
  raise
ensure
  if !rack_skipped && headers && TraceView::XTrace.valid?(xtrace)
    unless defined?(JRUBY_VERSION) && TraceView.is_continued_trace?
      headers['X-Trace'] = xtrace if headers.is_a?(Hash)
    end
  end
end

#collect(req, env) ⇒ Object 



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# File 'lib/traceview/inst/rack.rb', line 28

def collect(req, env)
  report_kvs = {}

  begin
    report_kvs[:'HTTP-Host']        = req.host
    report_kvs[:Port]             = req.port
    report_kvs[:Proto]            = req.scheme
    report_kvs[:Method]            = req.request_method
    report_kvs[:AJAX]             = true if req.xhr?
    report_kvs[:ClientIP]         = req.ip

    if TraceView::Config[:rack][:log_args]
      report_kvs[:'Query-String']     = ::CGI.unescape(req.query_string) unless req.query_string.empty?
    end

    # Report any request queue'ing headers.  Report as 'Request-Start' or the summed Queue-Time
    report_kvs[:'Request-Start']     = env['HTTP_X_REQUEST_START']    if env.key?('HTTP_X_REQUEST_START')
    report_kvs[:'Request-Start']     = env['HTTP_X_QUEUE_START']      if env.key?('HTTP_X_QUEUE_START')
    report_kvs[:'Queue-Time']        = env['HTTP_X_QUEUE_TIME']       if env.key?('HTTP_X_QUEUE_TIME')

    report_kvs[:'Forwarded-For']     = env['HTTP_X_FORWARDED_FOR']    if env.key?('HTTP_X_FORWARDED_FOR')
    report_kvs[:'Forwarded-Host']    = env['HTTP_X_FORWARDED_HOST']   if env.key?('HTTP_X_FORWARDED_HOST')
    report_kvs[:'Forwarded-Proto']   = env['HTTP_X_FORWARDED_PROTO']  if env.key?('HTTP_X_FORWARDED_PROTO')
    report_kvs[:'Forwarded-Port']    = env['HTTP_X_FORWARDED_PORT']   if env.key?('HTTP_X_FORWARDED_PORT')

    report_kvs[:'Ruby.TraceView.Version'] = ::TraceView::Version::STRING
    report_kvs[:ProcessID]         = Process.pid
    report_kvs[:ThreadID]          = Thread.current.to_s[/0x\w*/]
  rescue StandardError => e
    # Discard any potential exceptions. Debug log and report whatever we can.
    TraceView.logger.debug "[traceview/debug] Rack KV collection error: #{e.inspect}"
  end
  report_kvs
end