From 96f905f40913b915496039d188297a7949b1a6db Mon Sep 17 00:00:00 2001 From: ThibG Date: Wed, 6 Mar 2019 19:53:57 +0100 Subject: [PATCH] Add optimistic lock to avoid race conditions when handling votes (#10196) * Add optimistic lock to avoid race conditions when handling votes * Force-reload polls when getting `ActiveRecord::StaleObjectError` --- app/models/poll.rb | 1 + app/models/poll_vote.rb | 3 +++ db/migrate/20190306145741_add_lock_version_to_polls.rb | 6 ++++++ db/schema.rb | 3 ++- 4 files changed, 12 insertions(+), 1 deletion(-) create mode 100644 db/migrate/20190306145741_add_lock_version_to_polls.rb diff --git a/app/models/poll.rb b/app/models/poll.rb index ab7236d455..da2e25e715 100644 --- a/app/models/poll.rb +++ b/app/models/poll.rb @@ -15,6 +15,7 @@ # last_fetched_at :datetime # created_at :datetime not null # updated_at :datetime not null +# lock_version :integer default(0), not null # class Poll < ApplicationRecord diff --git a/app/models/poll_vote.rb b/app/models/poll_vote.rb index 9ad66bbf8c..ad24eb6914 100644 --- a/app/models/poll_vote.rb +++ b/app/models/poll_vote.rb @@ -32,5 +32,8 @@ class PollVote < ApplicationRecord def increment_counter_cache poll.cached_tallies[choice] = (poll.cached_tallies[choice] || 0) + 1 poll.save + rescue ActiveRecord::StaleObjectError + poll.reload + retry end end diff --git a/db/migrate/20190306145741_add_lock_version_to_polls.rb b/db/migrate/20190306145741_add_lock_version_to_polls.rb new file mode 100644 index 0000000000..cf506404da --- /dev/null +++ b/db/migrate/20190306145741_add_lock_version_to_polls.rb @@ -0,0 +1,6 @@ +class AddLockVersionToPolls < ActiveRecord::Migration[5.2] + def change + add_column :polls, :lock_version, :integer, null: false, default: 0 + end +end + diff --git a/db/schema.rb b/db/schema.rb index 161619dcf5..3d52602709 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_03_04_152020) do +ActiveRecord::Schema.define(version: 2019_03_06_145741) do # These are extensions that must be enabled in order to support this database enable_extension "plpgsql" @@ -464,6 +464,7 @@ ActiveRecord::Schema.define(version: 2019_03_04_152020) do t.datetime "last_fetched_at" t.datetime "created_at", null: false t.datetime "updated_at", null: false + t.integer "lock_version", default: 0, null: false t.index ["account_id"], name: "index_polls_on_account_id" t.index ["status_id"], name: "index_polls_on_status_id" end