EtsLock

EtsLock is an Elixir library for acquiring exclusive locks on data in ETS tables.

Using with_ets_lock/4, you can process all {key, value} tuples for a given key while being sure other processes using with_ets_lock/4 are not mutating the data stored for this key.

Processing is performed in a separate process so that an execution timeout (:exec_timeout) can be enforced.

For high concurrent performance, all locks are stored in a separate ETS table, and no GenServers or other processes are used to coordinate access. This is in contrast to the (erlang-ets-lock library)[https://github.com/afiskon/erlang-ets-lock/], which uses a single GenServer to serialize access to ETS.

Docs

Full documentation is available on (Hexdocs.pm)[https://hexdocs.pm/ets_lock/EtsLock.html].

Example usage

iex> table = :ets.new(:whatever, [:set, :public]) iex> spawn(fn -> ...> ## Wait 50ms, try to acquire lock, then insert ...> Process.sleep(50) ...> EtsLock.with_ets_lock(table, :key, fn _ -> ...> :ets.insert(table, {:key, :yup}) ...> end) ...> end) iex> spawn(fn -> ...> ## Acquire lock immediately, hold it for 100ms, then insert ...> EtsLock.with_ets_lock(table, :key, fn _ -> ...> Process.sleep(100) ...> :ets.insert(table, {:key, :nope}) ...> end) ...> end) iex> Process.sleep(200) iex> :ets.lookup(table, :key) [{:key, :yup}]

Options

• :wait_timeout - Milliseconds to wait when acquiring a lock. Default 5000. Set to :infinity to try forever to acquire a lock.

• :exec_timeout - Milliseconds to allow fun to hold the lock before its execution is cancelled and the lock is released. Default 5000. Set to :infinity to hold the lock indefinitely until fun has finished.

• :fail_timeout - Milliseconds to wait before forcibly deleting a lock after it should have been released, but wasn't. Default 1000. Provides protection against permanently hanging locks in the case that both the caller and the spawned task crash. Set to :infinity to disable this protection (not recommended).

• :spin_delay - Milliseconds to wait between every attempt to acquire a lock. Default 2.

• :lock_table - ETS table in which to store locks. Default EtsLock.Locks.

Installation

Add ets_lock to your list of dependencies in mix.exs:

def deps do
  [
    {:ets_lock, "~> 0.2.0"}
  ]
end

Authorship and License

EtsLock is copyright 2019, Appcues, Inc.

EtsLock is released under the MIT License, available at LICENSE.txt.