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Erlang Server SDK

Statsig server SDK for Erlang applications. This SDK is open source and hosted on github.

The Basics

Get started in a few quick steps.

  1. Create a free account on statsig.com
  2. Install the SDK
  3. Initialize the SDK
  4. Fetch Feature Gates, Dynamic Configs, or Experiments
  5. Log a custom event

Step 1 - Create a free account on www.statsig.com

You could skip this for now, but you will need an SDK Key and some Feature Gates or Dynamic Configs to use with the SDK in just a minute.

Step 2 - Install the SDK

warning

This is a pre-release version of the erlang/elixir SDK. You can use the main branch at your own risk

Add a dependency on statsig to your rebar config:

{deps, [..., {statsig,".*",{git,"https://github.com/statsig-io/erlang-sdk",{branch, main}}}]}.

Step 3 - 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 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 synchronous1--the SDK will fetch updates from Statsig in the background, independently of your API calls.

Step 4 - Fetch Feature Gates, Dynamic Configs, or Experiments

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),

Then we have Experiments, which you can use to run A/B/n experiments and use advanced features like layers (coming soon) to avoid collision and enable quicker iterations with parameter reuse.

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

Step 5 - Log a custom 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.

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 down Statsig

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)

Reference

(Coming soon)

FAQ

How do I run experiments for logged out users?

You can run experiments for arbitrary unit IDs (sessionID, groupID, etc), rather than at the userID level, if you choose. These custom unit IDs must be predefined in your Statsig project, and then selected in the Experiment creation flow. For more information, see our guide on experimenting on custom ID types