Nebulex.Adapters.Redis

Nebulex adapter for Redis (including Redis Cluster support).

About

This adapter uses Redix; a Redis driver for Elixir.

The adapter supports different configurations modes which are explained in the next sections.

[!NOTE]
This README refers to the main branch of nebulex_redis_adapter, not the latest released version on Hex. Please reference the official documentation for the latest stable release.

Installation

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

defp deps do
  [
    {:nebulex_redis_adapter, "~> 3.0.0-rc.1"},
    {:crc, "~> 0.10"},        #=> Needed when using `:redis_cluster` mode
    {:ex_hash_ring, "~> 6.0"} #=> Needed when using `:client_side_cluster` mode
  ]
end

The adapter dependencies are optional to give more flexibility and loading only needed ones. For example:

:crc - Required when using the adapter in mode :redis_cluster. See Redis Cluster.
:ex_hash_ring - Required when using the adapter in mode :client_side_cluster.

Then run mix deps.get to fetch the dependencies.

Usage

After installing, we can define our cache to use Redis adapter as follows:

defmodule MyApp.RedisCache do
  use Nebulex.Cache,
    otp_app: :my_app,
    adapter: Nebulex.Adapters.Redis
end

The rest of Redis configuration is set in our application environment, usually defined in your config/config.exs:

config :my_app, MyApp.RedisCache,
  conn_opts: [
    # Redix options
    host: "127.0.0.1",
    port: 6379
  ]

Since this adapter is implemented by means of Redix, it inherits the same options, including regular Redis options and connection options as well. For more information about the options, please check out Nebulex.Adapters.Redis module and also Redix.

See online documentation and Redis cache example for more information.

Distributed Caching

There are different ways to support distributed caching when using Nebulex.Adapters.Redis.

Redis Cluster

Redis Cluster is a built-in feature in Redis since version 3, and it may be the most convenient and recommendable way to set up Redis in a cluster and have a distributed cache storage out-of-box. This adapter provides the :redis_cluster mode to set up Redis Cluster from the client-side automatically and be able to use it transparently.

First of all, ensure you have Redis Cluster configured and running.

Then we can define our cache which will use Redis Cluster:

defmodule MyApp.RedisClusterCache do
  use Nebulex.Cache,
    otp_app: :my_app,
    adapter: Nebulex.Adapters.Redis
end

The config:

config :my_app, MyApp.RedisClusterCache,
  # Enable redis_cluster mode
  mode: :redis_cluster,

  # For :redis_cluster mode this option must be provided
  redis_cluster: [
    # Configuration endpoints
    # This is where the client will connect and send the "CLUSTER SHARDS"
    # (Redis >= 7) or "CLUSTER SLOTS" (Redis < 7) command to get the cluster
    # information and set it up on the client side.
    configuration_endpoints: [
      endpoint1_conn_opts: [
        host: "127.0.0.1",
        port: 6379,
        # Add the password if &#39;requirepass&#39; is on
        password: "password"
      ]
    ]
  ]

The pool of connections to the different master nodes is automatically configured by the adapter once it gets the cluster slots info.

This one could be the easiest and recommended way for distributed caching using Redis and Nebulex.Adapters.Redis.

Client-side Cluster

Nebulex.Adapters.Redis also brings with a simple client-side cluster implementation based on sharding distribution model.

We define our cache normally:

defmodule MyApp.ClusteredCache do
  use Nebulex.Cache,
    otp_app: :my_app,
    adapter: Nebulex.Adapters.Redis
end

The config:

config :my_app, MyApp.ClusteredCache,
  # Enable client-side cluster mode
  mode: :client_side_cluster,

  # For :client_side_cluster mode this option must be provided
  client_side_cluster: [
    # Nodes config (each node has its own options)
    nodes: [
      node1: [
        # Node pool size
        pool_size: 10,

        # Redix options to establish the pool of connections against this node
        conn_opts: [
          host: "127.0.0.1",
          port: 9001
        ]
      ],
      node2: [
        pool_size: 4,
        conn_opts: [
          url: "redis://127.0.0.1:9002"
        ]
      ],
      node3: [
        conn_opts: [
          host: "127.0.0.1",
          port: 9003
        ]
      ]
      # Maybe more ...
    ]
  ]

Using a Redis Proxy

The other option is to use a proxy, like Envoy proxy or Twemproxy on top of Redis. In this case, the proxy does the distribution work, and from the adparter's side (Nebulex.Adapters.Redis), it would be only configuration. Instead of connect the adapter against the Redis nodes, we connect it against the proxy nodes, this means, in the config, we setup the pool with the host and port pointing to the proxy.

Using the adapter as a Redis client

Since the Redis adapter works on top of Redix and provides features like connection pools, "Redis Cluster", etc., it may also work as a Redis client. The Redis API is quite extensive, and there are many useful commands we may want to run, leveraging the Redis adapter features. Therefore, the adapter provides additional functions to do so.

iex> conn = MyCache.fetch_conn!()
iex> Redix.command!(conn, ["LPUSH", "mylist", "world"])
1
iex> Redix.command!(conn, ["LPUSH", "mylist", "hello"])
2
iex> Redix.command!(conn, ["LRANGE", "mylist", "0", "-1"])
["hello", "world"]

iex> conn = MyCache.fetch_conn!(key: "mylist")
iex> Redix.pipeline!(conn, [
...>   ["LPUSH", "mylist", "world"],
...>   ["LPUSH", "mylist", "hello"],
...>   ["LRANGE", "mylist", "0", "-1"]
...> ])
[1, 2, ["hello", "world"]]

[!NOTE]
The :name may be needed when using dynamic caches, and the :key is required when using the :redis_cluster or :client_side_cluster mode.

Testing

To run the Nebulex.Adapters.Redis tests you will have to have Redis running locally. Nebulex.Adapters.Redis requires a complex setup for running tests (since it needs a few instances running, for standalone, cluster and Redis Cluster). For this reason, there is a docker-compose.yml file in the repo so that you can use Docker and docker-compose to spin up all the necessary Redis instances with just one command. Make sure you have Docker installed and then just run:

$ docker-compose up

Since Nebulex.Adapters.Redis uses the support modules and shared tests from Nebulex and by default its test folder is not included in the Hex dependency, the following steps are required for running the tests.

First of all, make sure you set the environment variable NEBULEX_PATH to nebulex:

export NEBULEX_PATH=nebulex

Second, make sure you fetch :nebulex dependency directly from GtiHub by running:

mix nbx.setup

Third, fetch deps:

mix deps.get

Finally, you can run the tests:

mix test

Running tests with coverage:

mix coveralls.html

You will find the coverage report within cover/excoveralls.html.

Benchmarks

Benchmarks were added using benchee; to learn more, see the benchmarks directory.

To run the benchmarks:

$ MIX_ENV=test mix run benchmarks/benchmark.exs

Benchmarks use default Redis options (host: "127.0.0.1", port: 6379).

Contributing

Contributions to Nebulex 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 mix test.ci and ensure all checks run successfully.

Copyright and License

Nebulex.Adapters.Redis source code is licensed under the MIT License.