ORM call in async or concurrent context (ARCH6043)

Key ruby.async.activerecord-in-thread · Severity warning · Category async

ActiveRecord checks out one connection per thread. Spawned threads that do not manage the connection explicitly drain the pool and never return their connections. Each thread should wrap its core work in with_connection (or checkout/checkin).

Incorrect

ids.each_slice(100).map do |slice|
  Thread.new do
    User.where(id: slice).update_all(active: true)
  end
end.each(&:join)

Correct

ids.each_slice(100).map do |slice|
  Thread.new do
    ActiveRecord::Base.connection_pool.with_connection do
      User.where(id: slice).update_all(active: true)
    end
  end
end.each(&:join)

Fix

Wrap every ORM call inside a thread in ActiveRecord::Base.connection_pool.with_connection so the connection returns to the pool.