Add ActionCable support

lib/appsignal/hooks.rb

@@ -86,6 +86,7 @@ def extract_value(object_or_hash, field, default_value = nil, convert_to_s = fal
   end
 end
 
+require "appsignal/hooks/action_cable"
 require "appsignal/hooks/active_support_notifications"
 require "appsignal/hooks/celluloid"
 require "appsignal/hooks/delayed_job"

lib/appsignal/hooks/action_cable.rb

@@ -0,0 +1,99 @@
+module Appsignal
+  class Hooks
+    # @api private
+    class ActionCableHook < Appsignal::Hooks::Hook
+      register :action_cable
+
+      def dependencies_present?
+        defined?(::ActiveSupport::Notifications::Instrumenter) &&
+          defined?(::ActionCable)
+      end
+
+      def install
+        patch_perform_action
+        install_callbacks
+      end
+
+      private
+
+      def patch_perform_action
+        ActionCable::Channel::Base.class_eval do
+          alias_method :original_perform_action, :perform_action
+
+          def perform_action(*args, &block)
+            # The request is only the original websocket request
+            request = ActionDispatch::Request.new(connection.env)
+            transaction = Appsignal::Transaction.create(
+              request.request_id,
+              Appsignal::Transaction::ACTION_CABLE,
+              request
+            )
+
+            begin
+              original_perform_action(*args, &block)
+            rescue => exception
+              transaction.set_error(exception)
+              raise exception
+            ensure
+              transaction.params = args.first
+              transaction.set_action_if_nil("#{self.class}##{args.first["action"]}")
+              transaction.set_metadata("path", request.path)
+              transaction.set_metadata("method", "websocket")
+              Appsignal::Transaction.complete_current!
+            end
+          end
+        end
+      end
+
+      def install_callbacks
+        ActionCable::Channel::Base.set_callback :subscribe, :around, :prepend => true do |channel, inner|
+          # The request is only the original websocket request
+          request = ActionDispatch::Request.new(channel.connection.env)
+          transaction = Appsignal::Transaction.create(
+            request.request_id,
+            Appsignal::Transaction::ACTION_CABLE,
+            request
+          )
+
+          begin
+            Appsignal.instrument "subscribed.action_cable" do
+              inner.call
+            end
+          rescue => exception
+            transaction.set_error(exception)
+            raise exception
+          ensure
+            transaction.set_action_if_nil("#{channel.class}#subscribed")
+            transaction.set_metadata("path", request.path)
+            transaction.set_metadata("method", "websocket")
+            Appsignal::Transaction.complete_current!
+          end
+        end
+
+        ActionCable::Channel::Base.set_callback :unsubscribe, :around, :prepend => true do |channel, inner|
+          # The request is only the original websocket request
+          request = ActionDispatch::Request.new(channel.connection.env)
+          transaction = Appsignal::Transaction.create(
+            request.request_id,
+            Appsignal::Transaction::ACTION_CABLE,
+            request
+          )
+
+          begin
+            Appsignal.instrument "unsubscribed.action_cable" do
+              inner.call
+            end
+          rescue => exception
+            transaction.set_error(exception)
+            raise exception
+          ensure
+            transaction.set_action_if_nil("#{channel.class}#unsubscribed")
+            transaction.set_metadata("path", request.path)
+            transaction.set_metadata("method", "websocket")
+            Appsignal::Transaction.complete_current!
+          end
+        end
+      end
+    end
+  end
+end

lib/appsignal/transaction.rb

@@ -4,6 +4,7 @@ module Appsignal
   class Transaction
     HTTP_REQUEST   = "http_request".freeze
     BACKGROUND_JOB = "background_job".freeze
+    ACTION_CABLE   = "action_cable".freeze
     FRONTEND       = "frontend".freeze
     BLANK          = "".freeze