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# Shards
> ### ETS tables on steroids!
> Sharding support for ETS tables out-of-box.
[](https://github.com/cabol/shards/actions)
[](https://hex.pm/packages/shards)
Why might we need **Sharding** on ETS tables? Well, the main reason is
to keep the lock contention under control, in order to scale-out ETS tables
(linearly) 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][sharding] or [Partitioning][partitioning]; the principle
is pretty similar to [DHTs][dht].
This is where **Shards** comes in. **Shards** is an **Erlang/Elixir** library
compatible with the current [ETS API][ets_api], which implements
[Sharding][sharding] or [Partitioning][partitioning] on top of ETS tables,
completely transparent and out-of-box.
See the [getting started][getting_started] guide
and the [online documentation](https://hexdocs.pm/shards/).
> [List of compatible ETS functions](https://github.com/cabol/shards/issues/1)
[ets_api]: http://erlang.org/doc/man/ets.html
[sharding]: https://en.wikipedia.org/wiki/Shard_(database_architecture)
[partitioning]: https://en.wikipedia.org/wiki/Partition_(database)
[dht]: https://en.wikipedia.org/wiki/Distributed_hash_table
[getting_started]: https://github.com/cabol/shards/blob/master/guides/getting-started.md
## Installation
### Erlang
In your `rebar.config`:
```erlang
{deps, [
{shards, "0.6.1"}
]}.
```
### Elixir
In your `mix.exs`:
```elixir
def deps do
[{:shards, "~> 0.6"}]
end
```
> Check out the [getting started][getting_started] guide to learn
more about it.
## Important links
* [Documentation](https://hexdocs.pm/shards) - Hex Docs.
* [Blog Post](http://cabol.github.io/posts/2016/04/14/sharding-support-for-ets.html) -
Transparent and out-of-box sharding support for ETS tables in Erlang/Elixir.
* [ExShards](https://github.com/cabol/ex_shards) – Elixir wrapper for
`shards`; with extra and nicer functions.
* [Nebulex](https://github.com/cabol/nebulex) – Distributed Caching
framework for Elixir.
* [KVX](https://github.com/cabol/kvx) – Simple Elixir in-memory Key/Value
Store using `shards` (default adapter).
* [Cacherl](https://github.com/ferigis/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`).
## Building Edoc
```
$ make doc
```
> **NOTE:** Once you run the previous command, a new folder `doc` is created,
and you'll have a pretty nice HTML documentation.
## Copyright and License
Copyright (c) 2016 Carlos Andres Bolaños R.A.
**Shards** source code is licensed under the [MIT License](LICENSE.md).
