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`
This commit is contained in:
ThibG 2019-03-06 19:53:57 +01:00 committed by Eugen Rochko
parent b3668a79ec
commit 96f905f409
4 changed files with 12 additions and 1 deletions

View file

@ -15,6 +15,7 @@
# last_fetched_at :datetime # last_fetched_at :datetime
# created_at :datetime not null # created_at :datetime not null
# updated_at :datetime not null # updated_at :datetime not null
# lock_version :integer default(0), not null
# #
class Poll < ApplicationRecord class Poll < ApplicationRecord

View file

@ -32,5 +32,8 @@ class PollVote < ApplicationRecord
def increment_counter_cache def increment_counter_cache
poll.cached_tallies[choice] = (poll.cached_tallies[choice] || 0) + 1 poll.cached_tallies[choice] = (poll.cached_tallies[choice] || 0) + 1
poll.save poll.save
rescue ActiveRecord::StaleObjectError
poll.reload
retry
end end
end end

View file

@ -0,0 +1,6 @@
class AddLockVersionToPolls < ActiveRecord::Migration[5.2]
def change
add_column :polls, :lock_version, :integer, null: false, default: 0
end
end

View file

@ -10,7 +10,7 @@
# #
# It's strongly recommended that you check this file into your version control system. # 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 # These are extensions that must be enabled in order to support this database
enable_extension "plpgsql" enable_extension "plpgsql"
@ -464,6 +464,7 @@ ActiveRecord::Schema.define(version: 2019_03_04_152020) do
t.datetime "last_fetched_at" t.datetime "last_fetched_at"
t.datetime "created_at", null: false t.datetime "created_at", null: false
t.datetime "updated_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 ["account_id"], name: "index_polls_on_account_id"
t.index ["status_id"], name: "index_polls_on_status_id" t.index ["status_id"], name: "index_polls_on_status_id"
end end