Shards

ETS tables on steroids!

Sharding for ETS tables out-of-box.

Why might we need Sharding/Partitioning for the ETS tables? The main reason is to keep the lock contention under control enabling ETS tables to scale out and support higher levels of concurrency without lock issues; specially write-locks, which most of the cases might cause significant performance degradation.

Therefore, one of the most common and proven strategies to deal with these problems is Sharding or Partitioning; the principle is pretty similar to DHTs.

This is where shards comes in. Shards is an Erlang/Elixir library fully compatible with the ETS API, but it implements sharding or partitioning on top of the ETS tables, completely transparent and out-of-box.

See the getting started guide and the online documentation.

Installation

Erlang

In your rebar.config:

{deps, [
  {shards, "~> 1.0"}
]}.

Elixir

In your mix.exs:

def deps do
  [{:shards, "~> 1.0"}]
end

For more information and examples, see the getting started guide.

Important links

• Documentation - Hex Docs.

• Blog Post - Transparent and out-of-box sharding support for ETS tables in Erlang/Elixir.

• Projects using shards:

  • shards_dist - Distributed version of shards. It was moved to a separate repo since v1.0.0.
  • ExShards – Elixir wrapper for shards; with extra and nicer functions.
  • Nebulex – Distributed Caching framework for Elixir.
  • KVX – Simple Elixir in-memory Key/Value Store using shards (default adapter).
  • Cacherl Distributed Cache using shards.

Testing

$ make test

You can find tests results in _build/test/logs, and coverage in _build/test/cover.

NOTE: shards comes with a helper Makefile, but it is just a simple wrapper on top of rebar3, therefore, you can do everything using rebar3 directly as well (e.g.: rebar3 do ct, cover).

Generating Edoc

$ make docs

NOTE: Once you run the previous command, you will find the generated HTML documentation within doc folder; open doc/index.html.

Contributing

Contributions to shards are very welcome and appreciated!

Use the issue tracker for bug reports or feature requests. Open a pull request when you are ready to contribute.

When submitting a pull request you should not update the CHANGELOG.md, and also make sure you test your changes thoroughly, include unit tests alongside new or changed code.

Before to submit a PR it is highly recommended to run make check before and ensure all checks run successfully.

Copyright and License

Copyright (c) 2016 Carlos Andres Bolaños R.A.

Shards source code is licensed under the MIT License.