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 it’s 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 '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

If you are using Metal, be sure and extend the your Metal class with the Rack instrumentation:

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

Cascading or chained calls

You should avoid instrumenting nested calls. So if you are using Rack::Cascade to fall through the action, or you are chaining through to the next middleware which will have it’s own controller instrumentation, then you will want to instrument only when you are the endpoint.

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:

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

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 98

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 91

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 82

def call_with_newrelic(*args)
  @newrelic_env = args.first
  perform_action_with_newrelic_trace(:category => :rack, :params => {:uri => @newrelic_env['REQUEST_PATH']}) 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 79

def newrelic_request_headers
  @newrelic_env
end