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 configuration modes, which are explained in the following sections.

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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.

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🚀 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 provide more flexibility and load only the needed ones. For example:

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

Then run mix deps.get to fetch the dependencies.

💻 Usage

After installing, you can define your cache to use the Redis adapter as follows:

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

The Redis configuration is set in your 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 using Redix, it inherits the same options, including regular Redis options and connection options. For more information about the options, please check out the Nebulex.Adapters.Redis module and also Redix.

See the 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 recommended way to set up Redis in a cluster and have distributed cache storage out-of-the-box. This adapter provides the :redis_cluster mode to set up Redis Cluster from the client-side automatically and use it transparently.

First, ensure you have Redis Cluster configured and running.

Then you can define your cache which will use Redis Cluster:

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

The configuration:

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 'requirepass' is enabled
        password: "password"
      ]
    ]
  ]

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

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

🔗 Client-side Cluster

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

Define your cache normally:

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

The configuration:

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 nodes...
    ]
  ]

🌉 Using a Redis Proxy

Another option is to use a proxy, such as Envoy proxy or Twemproxy, on top of Redis. In this case, the proxy handles the distribution work, and from the adapter's side (Nebulex.Adapters.Redis), it would only require configuration. Instead of connecting the adapter to the Redis nodes, you connect it to the proxy nodes. This means in the config, you set up 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 can also work as a Redis client. The Redis API is quite extensive, and there are many useful commands you 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 need to have Redis running locally. Nebulex.Adapters.Redis requires a complex setup for running tests (since it needs several instances running for standalone, cluster, and Redis Cluster modes). For this reason, there is a docker-compose.yml file in the repo so 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, make sure you set the environment variable NEBULEX_PATH to nebulex:

export NEBULEX_PATH=nebulex

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

mix nbx.setup

Third, fetch the dependencies:

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 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, including unit tests alongside new or changed code.

Before submitting a PR, it is highly recommended to run mix test.ci and ensure all checks run successfully.

📄 Copyright and License

Copyright (c) 2018, Carlos Bolaños.

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