Add solid queue support (#508)

Based entirely on existing Good Job work.

lib/scout_apm.rb

@@ -68,6 +68,7 @@ module ScoutApm
 require 'scout_apm/background_job_integrations/que'
 require 'scout_apm/background_job_integrations/legacy_sneakers'
 require 'scout_apm/background_job_integrations/good_job'
+require 'scout_apm/background_job_integrations/solid_queue'
 
 require 'scout_apm/framework_integrations/rails_2'
 require 'scout_apm/framework_integrations/rails_3_or_4'

lib/scout_apm/background_job_integrations/solid_queue.rb

@@ -0,0 +1,47 @@
+module ScoutApm
+  module BackgroundJobIntegrations
+    class SolidQueue
+      UNKNOWN_QUEUE_PLACEHOLDER = 'default'.freeze
+      attr_reader :logger
+
+      def name
+        :solid_queue
+      end
+
+      def present?
+        defined?(::SolidQueue::VERSION)
+      end
+
+      def forking?
+        false
+      end
+
+      def install
+        ActiveSupport.on_load(:active_job) do
+          include ScoutApm::Tracer
+
+          around_perform do |job, block|
+            req = ScoutApm::RequestManager.lookup
+            latency = Time.now - (job.scheduled_at || job.enqueued_at) rescue 0
+            req.annotate_request(queue_latency: latency)
+
+            begin
+              req.start_layer ScoutApm::Layer.new("Queue", job.queue_name.presence || UNKNOWN_QUEUE_PLACEHOLDER)
+              started_queue = true # Following Convention
+              req.start_layer ScoutApm::Layer.new("Job", job.class.name)
+              started_job = true # Following Convention
+
+              block.call
+            rescue
+              req.error!
+              raise
+            ensure
+              req.stop_layer if started_job
+              req.stop_layer if started_queue
+            end
+          end
+        end
+      end
+    end
+  end
+end

lib/scout_apm/environment.rb

@@ -32,6 +32,7 @@ class Environment
       ScoutApm::BackgroundJobIntegrations::Que.new,
       ScoutApm::BackgroundJobIntegrations::Faktory.new,
       ScoutApm::BackgroundJobIntegrations::GoodJob.new,
+      ScoutApm::BackgroundJobIntegrations::SolidQueue.new,
     ]
 
     FRAMEWORK_INTEGRATIONS = [