From ded6aed15e74e5a12aa28971b7bd2e2ba87283cd Mon Sep 17 00:00:00 2001
From: Andrei Prigorshnev <a.prigorshnev@gmail.com>
Date: Mon, 6 Feb 2023 20:32:45 +0400
Subject: [PATCH] FIX: avoid race condition when setting user status (#19817)
 (#20182)

This is a backport of 84e13e9.

We caught it in logs, race condition led to this error:

    ActiveRecord::RecordNotUnique
    (PG::UniqueViolation: ERROR:  duplicate key value violates unique constraint "user_statuses_pkey"
    DETAIL:  Key (user_id)=(15) already exists.)


The reason the problem happened was that we were checking if a user has status and if not inserting status:

    if user_status
      ...
    else
      self.user_status = UserStatus.create!(status)
    end

The problem is that it's possible that another request will insert status just after we check if status exists and just before our request call `UserStatus.create!(status)`. Using `upsert` fixes the problem because under the hood `upsert` generates the only SQL request that uses "INSERT ... ON CONFLICT DO UPDATE". So we do everything in one SQL query, and that query takes care of resolving possible conflicts.
---
 app/models/user.rb | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/app/models/user.rb b/app/models/user.rb
index d0d9846a433..51dd41348b5 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -1789,14 +1789,17 @@ class User < ActiveRecord::Base
   end
 
   def set_status!(description, emoji, ends_at = nil)
-    status = { description: description, emoji: emoji, set_at: Time.zone.now, ends_at: ends_at }
-
-    if user_status
-      user_status.update!(status)
-    else
-      self.user_status = UserStatus.create!(status)
-    end
+    status = {
+      description: description,
+      emoji: emoji,
+      set_at: Time.zone.now,
+      ends_at: ends_at,
+      user_id: id,
+    }
+    validate_status!(status)
+    UserStatus.upsert(status)
 
+    reload_user_status
     publish_user_status(user_status)
   end
 
@@ -2174,6 +2177,10 @@ class User < ActiveRecord::Base
       )
     SQL
   end
+
+  def validate_status!(status)
+    UserStatus.new(status).validate!
+  end
 end
 
 # == Schema Information