When running an application in multiple servers, we can end up have issues such as doubling our requests. That's the moment to recur to find a solution and here we are going to solve using locking.

Based on: https://medium.com/flatiron-labs/database-locking-with-ecto-in-elixir-9804cdbd1866

Futher exploring: using Ecto.Multi to create larger transactions and optimizing lock.

If available in Hex, the package can be installed by adding ecto_lock to your list of dependencies in mix.exs:

def deps do
  [
    {:ecto_lock, "~> 0.1.0"}
  ]
end

mix deps.get
mix ecto.gen.repo -r EctoLock.Repo
mix ecto.create
mix ecto.migrate

iex -S mix

On iex you can run:

EctoLock.Helper.create_invoices
EctoLock.Helper.bill_from_two_servers # true for loking

Documentation can be generated with ExDoc and published on HexDocs. Once published, the docs can be found at https://hexdocs.pm/ecto_lock.