Commit 96f905f4 authored by ThibG's avatar ThibG Committed by Eugen Rochko

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`
parent b3668a79
......@@ -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
......
......@@ -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
class AddLockVersionToPolls < ActiveRecord::Migration[5.2]
def change
add_column :polls, :lock_version, :integer, null: false, default: 0
end
end
......@@ -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
......
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