Use with_advisory_lock to lock/check if a publication is already in t…

…he make-me-finalizer process (see papyri#169)

Gemfile

@@ -41,5 +41,6 @@ gem 'warbler'
 gem 'puma'
 gem 'database_cleaner'
 gem 'sucker_punch', '~> 1.0'
+gem 'with_advisory_lock'
 
 gem 'test_after_commit', :group => :test

Gemfile.lock

@@ -165,6 +165,7 @@ GEM
     test_after_commit (0.4.1)
       activerecord (>= 3.2)
     thor (0.19.1)
+    thread_safe (0.3.5-java)
     tilt (1.4.1)
     timers (4.1.1)
       hitimes
@@ -180,6 +181,9 @@ GEM
       jruby-rack (>= 1.1.1, < 1.3)
       rake (>= 0.9.6)
       rubyzip (>= 0.9, < 1.2)
+    with_advisory_lock (3.0.0)
+      activerecord (>= 3.2)
+      thread_safe
 
 PLATFORMS
   java
@@ -215,6 +219,7 @@ DEPENDENCIES
   test_after_commit
   uglifier (>= 1.0.3)
   warbler
+  with_advisory_lock
 
 BUNDLED WITH
    1.11.2

app/controllers/publications_controller.rb

@@ -301,14 +301,18 @@ def become_finalizer
     # TODO make sure we don't steal it from someone who is working on it
     @publication = Publication.find(params[:id].to_s)
     original_publication_owner_id = @publication.owner.id
+
     @publication.with_lock do
-      #note this can only be called on a board owned publication
       if @publication.owner_type != "Board"
+        #note this can only be called on a board owned publication
         flash[:error] = "Can't change finalizer on non-board copy of publication."
         redirect_to show
+      elsif @publication.advisory_lock_exists?("become_finalizer_#{@publication.id}")
+        flash[:notice] = "Another user is currently making themselves the finalizer."
+        redirect_to show
+      else
+        SendToFinalizerJob.new.async.perform(@publication.id, @current_user.id)
       end
-
-      SendToFinalizerJob.new.async.perform(@publication.id, @current_user.id)
     end
 
     flash[:notice] = "Finalizer change running. Check back in a few minutes."

app/jobs/send_to_finalizer_job.rb

@@ -9,8 +9,10 @@ def perform(publication_id, user_id = nil)
       ActiveRecord::Base.connection_pool.with_connection do
         publication = Publication.find(publication_id)
         publication.with_lock do
-          user = User.find(user_id) unless user_id.nil?
-          publication.send_to_finalizer(user)
+          publication.with_advisory_lock("become_finalizer_#{publication_id}") do
+            user = User.find(user_id) unless user_id.nil?
+            publication.send_to_finalizer(user)
+          end
         end
       end
     ensure