Fix account deletion sometimes failing because of optimistic locks (m…

…astodon#16317) * Fix account deletion sometimes failing because of optimistic locks In some rare occasions[1], deleting accounts would fail with a `StaleObjectError` exception. Indeed, account deletion manually sets the `AccountStat` values without handling cases where the optimistic locking on `AccountStat` would fail. To my knowledge, with the rewrite of account counters in mastodon#15913, the `DeleteAccountService` is now the only place that changes the counters in a way that is not atomic. Since in this specific case, we do not care about the previous values of the account counters, it appears we don't need locking at all for this table anymore. [1]: https://discourse.joinmastodon.org/t/account-cant-be-deleted/3602 * Bump MAX_SUPPORTED_VERSION in maintenance script
hachyderm · Jun 2, 2021 · 526332c · 526332c
1 parent be8079f
commit 526332c
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Showing 5 changed files with 13 additions and 6 deletions.
diff --git a/app/models/account_stat.rb b/app/models/account_stat.rb
@@ -11,10 +11,11 @@
 #  created_at      :datetime         not null
 #  updated_at      :datetime         not null
 #  last_status_at  :datetime
-#  lock_version    :integer          default(0), not null
 #
 
 class AccountStat < ApplicationRecord
+  self.locking_column = nil
+
   belongs_to :account, inverse_of: :account_stat
 
   update_index('accounts#account', :account)

diff --git a/app/models/concerns/account_counters.rb b/app/models/concerns/account_counters.rb
@@ -49,7 +49,6 @@ def update_count!(key, value)
               ON CONFLICT (account_id) DO UPDATE
               SET #{key} = account_stats.#{key} + :value,
                   last_status_at = now(),
-                  lock_version = account_stats.lock_version + 1,
                   updated_at = now()
               RETURNING id;
             SQL
@@ -59,7 +58,6 @@ def update_count!(key, value)
                 VALUES (:account_id, :default_value, now(), now())
               ON CONFLICT (account_id) DO UPDATE
               SET #{key} = account_stats.#{key} + :value,
-                  lock_version = account_stats.lock_version + 1,
                   updated_at = now()
               RETURNING id;
             SQL

diff --git a/db/post_migrate/20210526193025_remove_lock_version_from_account_stats.rb b/db/post_migrate/20210526193025_remove_lock_version_from_account_stats.rb
@@ -0,0 +1,9 @@
+# frozen_string_literal: true
+
+class RemoveLockVersionFromAccountStats < ActiveRecord::Migration[5.2]
+  def change
+    safety_assured do
+      remove_column :account_stats, :lock_version, :integer, null: false, default: 0
+    end
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2021_05_07_001928) do
+ActiveRecord::Schema.define(version: 2021_05_26_193025) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
@@ -111,7 +111,6 @@
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
     t.datetime "last_status_at"
-    t.integer "lock_version", default: 0, null: false
     t.index ["account_id"], name: "index_account_stats_on_account_id", unique: true
   end
 

diff --git a/lib/mastodon/maintenance_cli.rb b/lib/mastodon/maintenance_cli.rb
@@ -14,7 +14,7 @@ def self.exit_on_failure?
     end
 
     MIN_SUPPORTED_VERSION = 2019_10_01_213028
-    MAX_SUPPORTED_VERSION = 2021_05_07_001928
+    MAX_SUPPORTED_VERSION = 2021_05_26_193025
 
     # Stubs to enjoy ActiveRecord queries while not depending on a particular
     # version of the code/database