From 13c16b4e95c134d883b54e796e842c7f72cbbe21 Mon Sep 17 00:00:00 2001
From: Eugen Rochko <eugen@zeonfederated.com>
Date: Thu, 4 May 2017 04:34:57 +0200
Subject: [PATCH] Likely fix #2458, fix #2031 - handle out-of-order deletes for
 statuses (#2734)

* Likely fix #2458, fix #2031 - handle out-of-order deletes for statuses

If a delete arrives before the original status, cache that information
for 6h, and if the original status arrives in that window, ignore it

* Add test case
---
 app/services/process_feed_service.rb       | 17 ++++++++-
 spec/services/process_feed_service_spec.rb | 44 ++++++++++++++++++++++
 2 files changed, 60 insertions(+), 1 deletion(-)

diff --git a/app/services/process_feed_service.rb b/app/services/process_feed_service.rb
index 4d23a6262..70c05c938 100644
--- a/app/services/process_feed_service.rb
+++ b/app/services/process_feed_service.rb
@@ -42,6 +42,11 @@ class ProcessFeedService < BaseService
     private
 
     def create_status
+      if redis.exists("delete_upon_arrival:#{id}")
+        Rails.logger.debug "Delete for status #{id} was queued, ignoring"
+        return
+      end
+
       Rails.logger.debug "Creating remote status #{id}"
       status, just_created = status_from_xml(@xml)
 
@@ -84,7 +89,13 @@ class ProcessFeedService < BaseService
     def delete_status
       Rails.logger.debug "Deleting remote status #{id}"
       status = Status.find_by(uri: id)
-      RemoveStatusService.new.call(status) unless status.nil?
+
+      if status.nil?
+        redis.setex("delete_upon_arrival:#{id}", 6 * 3_600, id)
+      else
+        RemoveStatusService.new.call(status)
+      end
+
       nil
     end
 
@@ -273,5 +284,9 @@ class ProcessFeedService < BaseService
     def account?(xml = @xml)
       !xml.at_xpath('./xmlns:author', xmlns: TagManager::XMLNS).nil?
     end
+
+    def redis
+      Redis.current
+    end
   end
 end
diff --git a/spec/services/process_feed_service_spec.rb b/spec/services/process_feed_service_spec.rb
index 19054ecd4..f16dda4d4 100644
--- a/spec/services/process_feed_service_spec.rb
+++ b/spec/services/process_feed_service_spec.rb
@@ -154,4 +154,48 @@ XML
     expect(created_statuses.first.reblog.account_id).to eq good_actor.id
     expect(created_statuses.first.reblog.text).to eq 'Overwatch rocks'
   end
+
+  it 'ignores statuses with an out-of-order delete' do
+    sender = Fabricate(:account, username: 'tracer', domain: 'overwatch.com')
+
+    delete_body = <<XML
+<?xml version="1.0"?>
+<entry xmlns="http://www.w3.org/2005/Atom" xmlns:thr="http://purl.org/syndication/thread/1.0" xmlns:activity="http://activitystrea.ms/spec/1.0/" xmlns:poco="http://portablecontacts.net/spec/1.0" xmlns:media="http://purl.org/syndication/atommedia" xmlns:ostatus="http://ostatus.org/schema/1.0" xmlns:mastodon="http://mastodon.social/schema/1.0">
+  <id>tag:overwatch.com,2017-04-27:objectId=4487555:objectType=Status</id>
+  <published>2017-04-27T13:49:25Z</published>
+  <updated>2017-04-27T13:49:25Z</updated>
+  <activity:object-type>http://activitystrea.ms/schema/1.0/note</activity:object-type>
+  <activity:verb>http://activitystrea.ms/schema/1.0/delete</activity:verb>
+  <author>
+    <id>https://overwatch.com/users/tracer</id>
+    <activity:object-type>http://activitystrea.ms/schema/1.0/person</activity:object-type>
+    <uri>https://overwatch.com/users/tracer</uri>
+    <name>tracer</name>
+  </author>
+</entry>
+XML
+
+    status_body = <<XML
+<?xml version="1.0"?>
+<entry xmlns="http://www.w3.org/2005/Atom" xmlns:thr="http://purl.org/syndication/thread/1.0" xmlns:activity="http://activitystrea.ms/spec/1.0/" xmlns:poco="http://portablecontacts.net/spec/1.0" xmlns:media="http://purl.org/syndication/atommedia" xmlns:ostatus="http://ostatus.org/schema/1.0" xmlns:mastodon="http://mastodon.social/schema/1.0">
+  <id>tag:overwatch.com,2017-04-27:objectId=4487555:objectType=Status</id>
+  <published>2017-04-27T13:49:25Z</published>
+  <updated>2017-04-27T13:49:25Z</updated>
+  <activity:object-type>http://activitystrea.ms/schema/1.0/note</activity:object-type>
+  <activity:verb>http://activitystrea.ms/schema/1.0/post</activity:verb>
+  <author>
+    <id>https://overwatch.com/users/tracer</id>
+    <activity:object-type>http://activitystrea.ms/schema/1.0/person</activity:object-type>
+    <uri>https://overwatch.com/users/tracer</uri>
+    <name>tracer</name>
+  </author>
+  <content type="html">Overwatch rocks</content>
+</entry>
+XML
+
+    subject.call(delete_body, sender)
+    created_statuses = subject.call(status_body, sender)
+
+    expect(created_statuses).to be_empty
+  end
 end