explicitely use transactions for messages seems to fix foodcoops#1055

plugins/messages/app/controllers/messages_controller.rb

@@ -31,13 +31,20 @@ def new
 
   # Creates a new message.
   def create
-    @message = @current_user.send_messages.new(params[:message])
-    if @message.save
-      DeliverMessageJob.perform_later(@message)
-      redirect_to messages_url, notice: I18n.t('messages.create.notice')
-    else
-      render action: 'new'
+    ActiveRecord::Base.transaction do
+      @current_user.with_lock do
+        @message = @current_user.send_messages.new(params[:message])
+        if @message.save
+          DeliverMessageJob.perform_later(@message)
+          redirect_to messages_url, notice: I18n.t('messages.create.notice')
+        else
+          raise ActiveRecord::Rollback # Rollback the transaction if the save fails
+        end
+      end
     end
+    rescue ActiveRecord::RecordInvalid => e
+      # Handle validation errors
+      render action: 'new'
   end
 
   # Shows a single message.

plugins/messages/app/mail_receivers/messages_mail_receiver.rb

@@ -31,24 +31,26 @@ def received(data)
     body = EmailReplyTrimmer.trim(body)
     raise BlankBodyException if body.empty?
 
-    message = @user.send_messages.new body: body,
-                                      group: @message.group,
-                                      private: @message.private,
-                                      received_email: data
-    message.reply_to_message = if @message.reply_to
-                                 @message.reply_to_message
-                               else
-                                 @message
-                               end
-    message.subject = if mail.subject
-                        mail.subject.gsub("[#{FoodsoftConfig[:name]}] ", '')
-                      else
-                        I18n.t('messages.model.reply_subject', subject: message.reply_to_message.subject)
-                      end
-    message.add_recipients [@message.sender_id]
+    ActiveRecord::Base.transaction do
+      message = @user.send_messages.new body: body,
+                                        group: @message.group,
+                                        private: @message.private,
+                                        received_email: data
+      message.reply_to_message = if @message.reply_to
+                                   @message.reply_to_message
+                                 else
+                                   @message
+                                 end
+      message.subject = if mail.subject
+                          mail.subject.gsub("[#{FoodsoftConfig[:name]}] ", '')
+                        else
+                          I18n.t('messages.model.reply_subject', subject: message.reply_to_message.subject)
+                        end
+      message.add_recipients [@message.sender_id]
 
-    message.save!
-    DeliverMessageJob.perform_later(message)
+      message.save!
+      DeliverMessageJob.perform_later(message)
+    end
   end
 
   private