Module: NewRelic::Agent::Instrumentation::Rack

Includes:
ControllerInstrumentation
Defined in:
lib/new_relic/agent/instrumentation/rack.rb

Overview

Instrumentation for Rack

New Relic will instrument a #call method as if it were a controller action, collecting transaction traces and errors. The middleware will be identified only by its class, so if you want to instrument multiple actions in a middleware, you need to use NewRelic::Agent::Instrumentation::ControllerInstrumentation::ClassMethods#add_transaction_tracer

Example:

require 'newrelic_rpm'
require 'new_relic/agent/instrumentation/rack'
class Middleware
  def call(env)
    ...
  end
  # Do the include after the call method is defined:
  include NewRelic::Agent::Instrumentation::Rack
end

Instrumenting Metal and Cascading Middlewares

Metal apps and apps belonging to Rack::Cascade middleware follow a convention of returning a 404 for all requests except the ones they are set up to handle. This means that New Relic needs to ignore these calls when they return a 404.

In these cases, you should not include or extend the Rack module but instead include NewRelic::Agent::Instrumentation::ControllerInstrumentation. Here’s how that might look for a Metal app:

require 'new_relic/agent/instrumentation/controller_instrumentation'
class MetalApp
  extend NewRelic::Agent::Instrumentation::ControllerInstrumentation
  def self.call(env)
    if should_do_my_thing?
      perform_action_with_newrelic_trace(:category => :rack) do
        return my_response(env)
      end
    else
      return [404, {"Content-Type" => "text/html"}, ["Not Found"]]
    end
  end
end

Overriding the metric name

By default the middleware is identified only by its class, but if you want to be more specific and pass in name, then omit including the Rack instrumentation and instead follow this example:

require 'newrelic_rpm'
require 'new_relic/agent/instrumentation/controller_instrumentation'
class Middleware
  include NewRelic::Agent::Instrumentation::ControllerInstrumentation
  def call(env)
    ...
  end
  add_transaction_tracer :call, :category => :rack, :name => 'my app'
end

Class Method Summary collapse

Instance Method Summary collapse

Methods included from ControllerInstrumentation

#newrelic_metric_path, #perform_action_with_newrelic_trace

Class Method Details

.extended(middleware) ⇒ Object

:nodoc:



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# File 'lib/new_relic/agent/instrumentation/rack.rb', line 87

def self.extended middleware #:nodoc:
  middleware.class_eval do
    class << self
      alias call_without_newrelic call
      alias call call_with_newrelic
    end
  end
end

.included(middleware) ⇒ Object

:nodoc:



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# File 'lib/new_relic/agent/instrumentation/rack.rb', line 80

def self.included middleware #:nodoc:
  middleware.class_eval do
    alias call_without_newrelic call
    alias call call_with_newrelic
  end
end

Instance Method Details

#call_with_newrelic(*args) ⇒ Object 



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# File 'lib/new_relic/agent/instrumentation/rack.rb', line 71

def call_with_newrelic(*args)
  @newrelic_request = ::Rack::Request.new(args.first)
  perform_action_with_newrelic_trace(:category => :rack, :request => @newrelic_request) do
    result = call_without_newrelic(*args)
    # Ignore cascaded calls
    MetricFrame.abort_transaction! if result.first == 404
    result
  end
end

#newrelic_request_headers ⇒ Object 



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# File 'lib/new_relic/agent/instrumentation/rack.rb', line 68

def newrelic_request_headers
  @newrelic_request.env
end