# Erlang Server SDK

## Getting Started​

The following will outline how to get up and running with Statsig for Erlang.

### Create an Account​

To work with the SDK, you will need a Statsig account. If you don't yet have an account, you can sign up for a free one here. You could skip this for now, but you will need an SDK key and some gates/experiments to use with the SDK in just a minute.

### Installation​

##### warning

We have not yet published a production version of the erlang SDK. The erlang SDK repository, and this docs site, are a work in progress. If you are trying to use Statsig in erlang or elixir, please reach out to support@statsig.com, or in our Slack community

% While developing the sdk/adding integration tests, you can depend on main% A production version of the sdk has not been published.  This sdk is a work in progress.{deps, [..., {statsig,".*",{git,"https://github.com/statsig-io/erlang-sdk",{branch, main}}}]}.

### Initialize the SDK​

After installation, you will need to initialize the SDK using a Server Secret Key from the statsig console.

##### info

Do NOT embed your Server Secret Key in client side applications, or expose it in any external facing documents. However, if you accidentally exposed it, you can create a new one in Statsig console.

There is also an optional parameter named options that allows you to pass in a StatsigOptions to customize the SDK.

Define the application in your .app.src.

{applications, [..., statsig]},

Set your server secret key as a config for the statsig application. In app.config, or your system configuration file

[{statsig, [statsig_api_key, <<"secret-">>]}].

Then, ensure statsig starts with:

application:ensure_all_started(statsig)
initialize will perform a network request. After initialize completes, virtually all SDK operations will be synchronous (See Evaluating Feature Gates in the Statsig SDK). The SDK will fetch updates from Statsig in the background, independently of your API calls.

## Working with the SDK​

### Checking a Gate​

Now that your SDK is initialized, let's fetch a Feature Gate. Feature Gates can be used to create logic branches in code that can be rolled out to different users from the Statsig Console. Gates are always CLOSED or OFF (think return false;) by default.

From this point on, all APIs will require you to specify the user (see Statsig user) associated with the request. For example, check a gate for a certain user like this:

User = #{<<"userID">> => UserID},GateVal = statsig:check_gate(User, GateName),

Feature Gates can be very useful for simple on/off switches, with optional but advanced user targeting. However, if you want to be able send a different set of values (strings, numbers, and etc.) to your clients based on specific user attributes, e.g. country, Dynamic Configs can help you with that. The API is very similar to Feature Gates, but you get an entire json object you can configure on the server and you can fetch typed parameters from it. For example:

User = #{<<"userID">> => UserID},Config = statsig:get_config(User, ConfigName),

### Getting an Layer/Experiment​

Then we have Layers/Experiments, which you can use to run A/B/n experiments. We offer two APIs, but we recommend the use of layers to enable quicker iterations with parameter reuse.

##### info

The Erland SDK currently only supports get_experiment. If you need the get_layer, please let us know

User = #{<<"userID">> => UserID},Experiment = statsig:get_experiment(User, ExperimentName),EnableFeature = maps:get(<<"feature_enabled">>, Experiment, false),

### Logging an Event​

Now that you have a Feature Gate or an Experiment set up, you may want to track some custom events and see how your new features or different experiment groups affect these events. This is super easy with Statsig - simply call the Log Event API and specify the user and event name to log; you additionally provide some value and/or an object of metadata to be logged together with the event:

User = #{<<"userID">> => UserID},EventName = <<"Purchase">>,Value = 100,Metadata = #{<<"category">> => <<"sport">>},statsig:log_event(User, EventName, Value, Metadata),

## Statsig User​

When calling APIs that require a user, you should pass as much information as possible in order to take advantage of advanced gate and config conditions (like country or OS/browser level checks), and correctly measure impact of your experiments on your metrics/events. The userID field is required because it's needed to provide a consistent experience for a given user (click here to understand further why it's important to always provide a userID).

Besides userID, we also have email, ip, userAgent, country, locale and appVersion as top-level fields on StatsigUser. In addition, you can pass any key-value pairs in an object/dictionary to the custom field and be able to create targeting based on them.

### Private Attributes​

Have sensitive user PII data that should not be logged? No problem, we have a solution for it! On the StatsigUser object we also have a field called privateAttributes, which is a simple object/dictionary that you can use to set private user attributes. Any attribute set in privateAttributes will only be used for evaluation/targeting, and removed from any logs before they are sent to Statsig server.

For example, if you have feature gates that should only pass for users with emails ending in "@statsig.com", but do not want to log your users' email addresses to Statsig, you can simply add the key-value pair { email: "my_user@statsig.com" } to privateAttributes on the user and that's it!

## Statsig Options​

You can specify optional parameters in the papplication config.

The available parameters are:

• statsig_api: default "https://statsigapi.net/v1/". The endpoint to use for network requests to load gates/experiments and flush log events
• statsig_polling_interval: default 60000, How frequently to poll for changes to gates/experiments in your statsig project, in ms
• statsig_environment_tier: default undefined, The environment tier to set for this instance of the statsig erlang sdk. "production", "staging", "development" or your own custom tiers

## Shutting Statsig Down​

Because we batch and periodically flush events, some events may not have been sent when your app/server shuts down.

To make sure all logged events are properly flushed, you should tell Statsig to shutdown when your app/server is closing:

statsig.flush()

Optionally followed by shutting down the application:

application:stop(statsig)