Zexbox

Installation

The can be installed by adding zexbox to your list of dependencies in mix.exs:

def deps do
  [
    {:zexbox, "~> 0.8.0"}
  ]
end

LaunchDarkly Feature Flags

Configuration

Configuration is fairly simple, with the only required piece of configuration being the sdk_key. For production environments we recommend also including :email as a private attribute:

config :zexbox, :flags,
  sdk_key: System.fetch_env!("LAUNCH_DARKLY_SDK_KEY"),
  private_attributes: [:email]

For local development and testing you'll probably want to read flags from a local file and ensure there is no interaction with the LaunchDarkly API. While the two configurations will be very similar you should have different ones to put to different files. You're configurations will look something like this following:

config :zexbox, :flags,
  sdk_key: "dev-launch-darkly-key",
  file_datasource: true,
  send_events: false,
  file_auto_update: true,
  file_poll_interval: 1000,
  feature_store: :ldclient_storage_map,
  file_paths: ["flags.json"]

Implementing

In order to use feature flags you need to start the LaunchDarkly client using. You should do this in the start/2 function of your Application module:

def start(_type, _args) do
  Zexbox.Flags.start()
  ...
end

You should laso make sure that the client shuts down when your app does in the stop/2 function of your Application module:

def stop(_type, _args) do
  Zexbox.Flags.stop()
  ...
end

Evaluating a flag can be achieved by simply calling the variation/3 function.

Zexbox.Flags.variation(
  "my-flag",
  %{key: "user-hash", email: "user@email.com"},
  "my_default_value"
)

Metrics and Logging

Configuration

In order to setup metrics with InfluxDB you'll need to add the following configuration

config :zexbox, Zexbox.Metrics.Connection,
  host: "localhost:8086",
  auth: [
    method: :token,
    token: "token"
  ],
  bucket: "my_app",
  org: "zappi",
  version: :v2

By default both metrics and logging will be enabled, you can customise this with the following configuration

config :zexbox, :features,
  capture_telemetry_metric_events: true,
  capture_telemetry_log_events: true

Implementing

In order to make use of metrics and logging you'll need to add the Zexbox module to your application's Supervisor tree

defmodule MyApp.Application do
  use Application

  @impl Application
  def start(_type, args) do
    ...
    children = [
      ...
      {Zexbox, []}
    ]
    ...
    Supervisor.start_link(children, opts)
  end
end

This will attach the telemetry and logging events to your controllers (assuming that they are enable in the :features config)

Adding Custom Controller Metrics

You can easily add your own controller metrics using the Zexbox.Metrics.Client module

metric = %Zexbox.Metrics.Series{
  measurement: "my_measurement",
  fields: %{
    "my_field" => 1
  },
  tags: %{
    "my_tag" => "my_value"
  }
}
Zexbox.Metrics.Client.write_metric(metric)

Copyright and License

Copyright (c) 2024, Zappistore.

Zexbox source code is licensed under the MIT License.