Class: Appsignal::Rack::EventHandler

Inherits:
Object
  • Object
show all
Includes:
Rack::Events::Abstract
Defined in:
lib/appsignal/rack/event_handler.rb

Overview

Instrumentation middleware using Rack’s Events module.

We recommend using this in combination with the InstrumentationMiddleware.

This middleware will report the response status code as the ‘response_status` tag on the sample. It will also report the response status as the `response_status` metric.

This middleware will ensure the AppSignal transaction is always completed for every request.

Examples:

Add EventHandler to a Rack app

# Add this middleware as the first middleware of an app
use ::Rack::Events, [Appsignal::Rack::EventHandler.new]

# Then add the InstrumentationMiddleware
use Appsignal::Rack::InstrumentationMiddleware

See Also:

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ EventHandler

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns a new instance of EventHandler.



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# File 'lib/appsignal/rack/event_handler.rb', line 43

def initialize
  @id = SecureRandom.uuid
end

Instance Attribute Details

#id ⇒ Object (readonly)

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/appsignal/rack/event_handler.rb', line 40

def id
  @id
end

Class Method Details

.safe_execution(name) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/appsignal/rack/event_handler.rb', line 31

def self.safe_execution(name)
  yield
rescue => e
  Appsignal.internal_logger.error(
    "Error occurred in #{name}: #{e.class}: #{e}: #{e.backtrace}"
  )
end

Instance Method Details

#on_error(request, _response, error) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/appsignal/rack/event_handler.rb', line 91

def on_error(request, _response, error)
  return unless Appsignal.active?

  self.class.safe_execution("Appsignal::Rack::EventHandler#on_error") do
    return unless request_handler?(request.env[APPSIGNAL_EVENT_HANDLER_ID])

    transaction = request.env[APPSIGNAL_TRANSACTION]
    return unless transaction

    request.env[APPSIGNAL_EVENT_HANDLER_HAS_ERROR] = true
    transaction.set_error(error)
  end
end

#on_finish(request, response) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/appsignal/rack/event_handler.rb', line 106

def on_finish(request, response)
  return unless Appsignal.active?
  return unless request_handler?(request.env[APPSIGNAL_EVENT_HANDLER_ID])

  transaction = request.env[APPSIGNAL_TRANSACTION]
  return unless transaction

  self.class.safe_execution("Appsignal::Rack::EventHandler#on_finish") do
    transaction.finish_event("process_request.rack", "", "")
    transaction.add_params_if_nil { request.params }
    transaction.add_headers_if_nil { request.env }
    transaction.add_session_data_if_nil do
      request.session if request.respond_to?(:session)
    end
    queue_start = Appsignal::Rack::Utils.queue_start_from(request.env)
    transaction.set_queue_start(queue_start) if queue_start
    response_status =
      if response
        response.status
      elsif request.env[APPSIGNAL_EVENT_HANDLER_HAS_ERROR] == true
        500
      end
    if response_status
      transaction.add_tags(:response_status => response_status)
      Appsignal.increment_counter(
        :response_status,
        1,
        :status => response_status,
        :namespace => format_namespace(transaction.namespace)
      )
    end
  end

  # Make sure the current transaction is always closed when the request
  # is finished
  Appsignal::Transaction.complete_current!
end

#on_start(request, _response) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future. 



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# File 'lib/appsignal/rack/event_handler.rb', line 53

def on_start(request, _response)
  return unless Appsignal.active?

  event_handler = self
  self.class.safe_execution("Appsignal::Rack::EventHandler#on_start") do
    request.env[APPSIGNAL_EVENT_HANDLER_ID] ||= id
    return unless request_handler?(request.env[APPSIGNAL_EVENT_HANDLER_ID])

    transaction = Appsignal::Transaction.create(Appsignal::Transaction::HTTP_REQUEST)
    request.env[APPSIGNAL_TRANSACTION] = transaction

    request.env[RACK_AFTER_REPLY] ||= []
    request.env[RACK_AFTER_REPLY] << proc do
      next unless event_handler.request_handler?(request.env[APPSIGNAL_EVENT_HANDLER_ID])

      Appsignal::Rack::EventHandler
        .safe_execution("Appsignal::Rack::EventHandler's after_reply") do
        transaction.finish_event("process_request.rack", "", "")
        queue_start = Appsignal::Rack::Utils.queue_start_from(request.env)
        transaction.set_queue_start(queue_start) if queue_start
      end

      # Make sure the current transaction is always closed when the request
      # is finished. This is a fallback for in case the `on_finish`
      # callback is not called. This is supported by servers like Puma and
      # Unicorn.
      #
      # The EventHandler.on_finish callback should be called first, this is
      # just a fallback if that doesn't get called.
      #
      # One such scenario is when a Puma "lowlevel_error" occurs.
      Appsignal::Transaction.complete_current!
    end
    transaction.start_event
  end
end

#request_handler?(given_id) ⇒ Boolean

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns:

  • (Boolean) 


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# File 'lib/appsignal/rack/event_handler.rb', line 48

def request_handler?(given_id)
  id == given_id
end