From 62f60e86c281ae1cd0356a7630dbb76069e2ffde Mon Sep 17 00:00:00 2001 From: Eugen Rochko Date: Wed, 2 Oct 2019 04:59:37 +0200 Subject: [PATCH] Fix account counters being overwritten by parallel writes (#12045) --- app/models/account_stat.rb | 22 ++++++++ ...13028_add_lock_version_to_account_stats.rb | 15 ++++++ db/schema.rb | 3 +- spec/models/account_stat_spec.rb | 53 +++++++++++++++++++ 4 files changed, 92 insertions(+), 1 deletion(-) create mode 100644 db/migrate/20191001213028_add_lock_version_to_account_stats.rb diff --git a/app/models/account_stat.rb b/app/models/account_stat.rb index 1351f7d8a4d..c84e4217c8c 100644 --- a/app/models/account_stat.rb +++ b/app/models/account_stat.rb @@ -11,6 +11,7 @@ # created_at :datetime not null # updated_at :datetime not null # last_status_at :datetime +# lock_version :integer default(0), not null # class AccountStat < ApplicationRecord @@ -20,10 +21,26 @@ class AccountStat < ApplicationRecord def increment_count!(key) update(attributes_for_increment(key)) + rescue ActiveRecord::StaleObjectError + begin + reload_with_id + rescue ActiveRecord::RecordNotFound + # Nothing to do + else + retry + end end def decrement_count!(key) update(key => [public_send(key) - 1, 0].max) + rescue ActiveRecord::StaleObjectError + begin + reload_with_id + rescue ActiveRecord::RecordNotFound + # Nothing to do + else + retry + end end private @@ -33,4 +50,9 @@ class AccountStat < ApplicationRecord attrs[:last_status_at] = Time.now.utc if key == :statuses_count attrs end + + def reload_with_id + self.id = find_by!(account: account).id if new_record? + reload + end end diff --git a/db/migrate/20191001213028_add_lock_version_to_account_stats.rb b/db/migrate/20191001213028_add_lock_version_to_account_stats.rb new file mode 100644 index 00000000000..47f37cca29d --- /dev/null +++ b/db/migrate/20191001213028_add_lock_version_to_account_stats.rb @@ -0,0 +1,15 @@ +require Rails.root.join('lib', 'mastodon', 'migration_helpers') + +class AddLockVersionToAccountStats < ActiveRecord::Migration[5.2] + include Mastodon::MigrationHelpers + + disable_ddl_transaction! + + def up + safety_assured { add_column_with_default :account_stats, :lock_version, :integer, allow_null: false, default: 0 } + end + + def down + remove_column :account_stats, :lock_version + end +end diff --git a/db/schema.rb b/db/schema.rb index 557b777e01f..2d516965c5f 100644 --- 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: 2019_09_27_232842) do +ActiveRecord::Schema.define(version: 2019_10_01_213028) do # These are extensions that must be enabled in order to support this database enable_extension "plpgsql" @@ -97,6 +97,7 @@ ActiveRecord::Schema.define(version: 2019_09_27_232842) do 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/spec/models/account_stat_spec.rb b/spec/models/account_stat_spec.rb index a94185109c7..8adc0d1d638 100644 --- a/spec/models/account_stat_spec.rb +++ b/spec/models/account_stat_spec.rb @@ -1,4 +1,57 @@ require 'rails_helper' RSpec.describe AccountStat, type: :model do + describe '#increment_count!' do + it 'increments the count' do + account_stat = AccountStat.create(account: Fabricate(:account)) + expect(account_stat.followers_count).to eq 0 + account_stat.increment_count!(:followers_count) + expect(account_stat.followers_count).to eq 1 + end + + it 'increments the count in multi-threaded an environment' do + account_stat = AccountStat.create(account: Fabricate(:account), statuses_count: 0) + increment_by = 15 + wait_for_start = true + + threads = Array.new(increment_by) do + Thread.new do + true while wait_for_start + AccountStat.find(account_stat.id).increment_count!(:statuses_count) + end + end + + wait_for_start = false + threads.each(&:join) + + expect(account_stat.reload.statuses_count).to eq increment_by + end + end + + describe '#decrement_count!' do + it 'decrements the count' do + account_stat = AccountStat.create(account: Fabricate(:account), followers_count: 15) + expect(account_stat.followers_count).to eq 15 + account_stat.decrement_count!(:followers_count) + expect(account_stat.followers_count).to eq 14 + end + + it 'decrements the count in multi-threaded an environment' do + account_stat = AccountStat.create(account: Fabricate(:account), statuses_count: 15) + decrement_by = 10 + wait_for_start = true + + threads = Array.new(decrement_by) do + Thread.new do + true while wait_for_start + AccountStat.find(account_stat.id).decrement_count!(:statuses_count) + end + end + + wait_for_start = false + threads.each(&:join) + + expect(account_stat.reload.statuses_count).to eq 5 + end + end end