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