From 34fa305a001f18855fea2711c8d44da65b84ef24 Mon Sep 17 00:00:00 2001
From: ThibG <thib@sitedethib.com>
Date: Tue, 19 Sep 2017 21:44:18 +0200
Subject: [PATCH] Fix race condition when processing incoming OStatus messages
 (#5013)

* Avoid races in incoming OStatus toots processing

* oops

* oops again
---
 app/lib/ostatus/activity/creation.rb | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

diff --git a/app/lib/ostatus/activity/creation.rb b/app/lib/ostatus/activity/creation.rb
index 4f4ef2971e..2687776f94 100644
--- a/app/lib/ostatus/activity/creation.rb
+++ b/app/lib/ostatus/activity/creation.rb
@@ -14,14 +14,22 @@ class OStatus::Activity::Creation < OStatus::Activity::Base
       return result if result.first.present?
     end
 
+    RedisLock.acquire(lock_options) do |lock|
+      if lock.acquired?
+        # Return early if status already exists in db
+        @status = find_status(id)
+        return [@status, false] unless @status.nil?
+        @status = process_status
+      end
+    end
+
+    [@status, true]
+  end
+
+  def process_status
     Rails.logger.debug "Creating remote status #{id}"
-
-    # Return early if status already exists in db
-    status = find_status(id)
-
-    return [status, false] unless status.nil?
-
     cached_reblog = reblog
+    status = nil
 
     ApplicationRecord.transaction do
       status = Status.create!(
@@ -55,7 +63,7 @@ class OStatus::Activity::Creation < OStatus::Activity::Base
     LinkCrawlWorker.perform_async(status.id) unless status.spoiler_text?
     DistributionWorker.perform_async(status.id)
 
-    [status, true]
+    status
   end
 
   def perform_via_activitypub
@@ -179,4 +187,8 @@ class OStatus::Activity::Creation < OStatus::Activity::Base
       Account.where(uri: href).or(Account.where(url: href)).first || FetchRemoteAccountService.new.call(href)
     end
   end
+
+  def lock_options
+    { redis: Redis.current, key: "create:#{id}" }
+  end
 end