# Zexbox
[](https://hex.pm/packages/zexbox)
[](https://github.com/Intellection/zexbox/actions/workflows/ci.yml)
[](https://hexdocs.pm/zexbox/api-reference.html)
## Installation
```elixir
def deps do
[
{:zexbox, "~> 1.4.1"}
]
end
```
## LaunchDarkly Feature Flags
The Zexbox library provides an idiomatic Elixir wrapper around the LaunchDarkly Erlang SDK with support for contexts, multi-contexts, and all modern LaunchDarkly features.
### 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:
```elixir
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](https://docs.launchdarkly.com/sdk/features/flags-from-files) 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:
```elixir
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. You should do this in the `start/2` function of your `Application` module:
```elixir
def start(_type, _args) do
Zexbox.Flags.start()
...
end
```
This will initialise a LauncDarkly client with the `:default` tag and using the configuration you've defined in your app.
If you wish to use a different tag you can make use of `Zexbox.Flags.start/1`
```elixir
Zexbox.Flags.start(:my_tag)
```
Additionally, if you don't want to make use of the application config you can use `Zexbox.Flags.start/2`
```elixir
Zexbox.Flags.start(
%{
sdk_key: "my-sdk-key", # This key is required
private_attributes: [:email]
},
:my_tag
)
```
You can then shut the `:default` client down when your app does in the `Zexbox.Flags.stop/0` function of your `Application` module:
```elixir
def stop(_type, _args) do
Zexbox.Flags.stop()
end
```
Stopping a client with a custom tag can be done using the `Zexbox.Flags.stop/1` function.
### Using Contexts
Contexts are the recommended way to evaluate feature flags. They provide type safety and support for multi-entity targeting:
```elixir
alias Zexbox.Flags.Context
# Simple user context
context = Context.new("user-123")
Zexbox.Flags.variation("my-flag", context, false)
# Context with attributes
context =
Context.new("user-123")
|> Context.set("email", "user@example.com")
|> Context.set("plan", "enterprise")
|> Context.set_private_attributes(["email"])
Zexbox.Flags.variation("premium-feature", context, false)
# Multi-context (target based on user AND organization)
user = Context.new("user-123", "user")
org = Context.new("org-456", "organization")
multi = Context.new_multi([user, org])
Zexbox.Flags.variation("enterprise-feature", multi, false)
```
**Backward Compatibility**: Raw maps are still supported:
```elixir
Zexbox.Flags.variation(
"my-flag",
%{key: "user-hash", email: "user@email.com"},
"my_default_value"
)
```
For more details, see the [Context Module Guide](CONTEXT_MODULE_GUIDE.md).
## Logging
Default logging can be attached to your controllers by calling `Zexbox.Logging.attach_controller_logs!` in the `start/2` function of your `Application` module:
```elixir
def start(_type, _args) do
Zexbox.Logging.attach_controller_logs!()
...
end
```
This sets up handlers for the `[:phoenix, :endpoint, :start]` and `[:phoenix, :endpoint, :stop]` [events](https://hexdocs.pm/phoenix/1.4.12/Phoenix.Endpoint.html#module-instrumentation) which are dispatched by `Plug.Telemetry` at the beginning and end of each request. The handlers are named `phoenix_controller_logs_stop` and `phoenix_controller_logs_start` respectively. The handlers log structured data (reports) in the following form `[info] [event: <event_params>, measurements: <measurement_data>, metadata: <metadat>, config: <config>]`.
### Adding your own logs
Adding your own logs is as simple as calling the `Zexbox.Telementry.attach/4` (which is just a wrapper around `:telemetry.attach/4`)
```elixir
Zexbox.Telemetry.attach(:my_event, [:my, :event], &MyAppHandler.my_handler/3, nil)
```
## Metrics
In order to setup metrics with InfluxDB you'll need to add the following configuration:
```elixir
config :zexbox, Zexbox.Metrics.Connection,
auth: [
method: :token,
token: "token"
],
host: "localhost",
port: "8086",
version: :v2,
org: "zappi",
bucket: "my_app"
```
A more indepth explanation on the configuration can be found in the `Instream.Connection` [hexdocs](https://hexdocs.pm/instream/Instream.html).
In order to make use of metrics you'll need to add the `Zexbox` module to your application's `Supervisor` tree
```elixir
defmodule MyApp.Application do
use Application
@impl Application
def start(_type, args) do
...
children = [
...
{Zexbox.Metrics, []}
]
...
Supervisor.start_link(children, opts)
end
end
```
This will write metrics to InfluxDB after every Phoenix DB request. The structure of the metrics is defined by the `Zexbox.Metrics.ControllerSeries` module.
### Adding Custom Controller Metrics
You can easily add your own controller metrics using the `Zexbox.Metrics.Client` module
```elixir
metric = %Zexbox.Metrics.Series{
measurement: "my_measurement",
fields: %{
"my_field" => 1
},
tags: %{
"my_tag" => "my_value"
}
}
Zexbox.Metrics.Client.write_metric(metric)
```
### Disabling Metrics For a Single Request/Process
If you want to suppress metrics for a specific request (for example: test traffic, synthetic checks, or health probes), disable metrics for the **current process**:
```elixir
Zexbox.Metrics.disable_for_process()
```
All metric writes from that process will be skipped (including the default controller metrics and any custom calls to `Zexbox.Metrics.Client.write_metric/1`). If you spawn tasks using `Task.async/1`, the disabled state is also respected in the spawned task via the caller chain.
To re-enable metrics for the current process:
```elixir
Zexbox.Metrics.enable_for_process()
```
## Copyright and License
Copyright (c) 2024, Zappistore.
Zexbox source code is licensed under the [MIT License](LICENSE.md).
