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Java/Kotlin Server SDK

Server vs. Client

These docs are for using our Java/Kotlin SDK in a multi-user, server side context. For client side android applications, check out our Android SDK or one of the other client SDKs for your client side applications.

This SDK is written in Kotlin, but exposes methods and overrides to Java based applications.

Installation​

v1.X.X+ of the SDK is now published only to Maven Central.

To install the SDK, set the Maven Central repository in your build.gradle. You probably already have this for other dependencies.

repositories {
    mavenCentral()
}

Then add the dependency:

implementation 'com.statsig:serversdk:1.X.X' // replace with the most up to date version
// For >v1.24.0 If you are not using streaming and want to reduce the package size you can:
implementation 'com.statsig:serversdk:1.X.X' {
    exclude(group = "io.grpc", module = "*") 
}

You can find the versions in the github releases of the open source sdk repository, or from the maven central repository.

Jitpack Deprecation​

v0.X.X versions of the SDK are available from jitpack, but newer versions will not be published to jitpack.

NOTE: If you update Statsig to be pulled from Maven Central instead of jitpack, you can remove maven { url 'https://jitpack.io' } if Statsig was the only library you got from jitpack and you previously relied on v0.X.X of the SDK.

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 expose it, you can create a new one in the Statsig console.

There is also an optional parameter named options that allows you to pass in a StatsigOptions to customize the SDK.
import com.statsig.sdk.Statsig;

StatsigOptions options = new StatsigOptions();
// Customize options as needed. For example:
// options.initTimeoutMs = 9999;
Future initFuture = Statsig.initializeAsync("server-secret-key", options);
initFuture.get();

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 Feature Flag/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:


StatsigUser user = new StatsigUser("user_id");
Boolean isFeatureOn = Statsig.checkGateSync(user, "use_new_feature");

if (isFeatureOn) {
  // Gate is on, use new feature
} else {
  // Gate is off
}

Reading a Dynamic Config​

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:


DynamicConfig config = Statsig.getConfigSync(user, "awesome_product_details");

// The 2nd parameter is the default value to be used in case the given parameter name does not exist on
// the Dynamic Config object. This can happen when there is a typo, or when the user is offline and the
// value has not been cached on the client.
String itemName = config.getString("product_name", "Awesome Product v1");
Double price = config.getDouble("price", 10.0);
Boolean shouldDiscount = config.getBoolean("discount", false);

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.

// Values via getLayer

Layer layer = Statsig.getLayerSync(user, "user_promo_experiments");
String promoTitle = layer.getString("title", "Welcome to Statsig!");
Double discount = layer.getDouble("discount", 0.1);

// or, via getExperiment

DynamicConfig titleExperiment = Statsig.getExperimentSync(user, "new_user_promo_title");
DynamicConfig priceExperiment = Statsig.getExperimentSync(user, "new_user_promo_price");

String promoTitle = titleExperiment.getString("title", "Welcome to Statsig!");
Double discount = priceExperiment.getDouble("discount", 0.1);

...

Double price = msrp * (1 - discount);

Asynchronous APIs

We mentioned earlier that after calling initialize most SDK APIs would run synchronously, so why are getConfig and checkGate asynchronous?

The main reason is that older versions of the SDK might not know how to interpret new types of gate conditions. In such cases the SDK will make an asynchronous call to our servers to fetch the result of a check. This can be resolved by upgrading the SDK, and we will warn you if this happens.

For more details, read our blog post about SDK evaluations. If you have any questions, please ask them in our Feedback Repository.

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:

Statsig.logEvent(user, "purchase", 2.99, Map.of("item_name", "remove_ads"));

Learn more about identifying users, group analytics, and best practices for logging events in the logging events guide.

Retrieving Feature Gate Metadata​

In certain scenarios, you may need more information about a gate evaluation than just a boolean value. For additional metadata about the evaluation, use the Get Feature Gate API, which returns a FeatureGate object


APIFeatureGate featureGate = Statsig.getFeatureGate(user, "a_gate");
System.out.println("Feature Gate: " + featureGate.getName() + ", Is Enabled?: " + featureGate.getValue());

String reason = featureGate.getReason() != null ? featureGate.getReason().toString() : "No specific reason";
System.out.println("Evaluation Reason: " + reason);

The APIFeatureGate data class encapsulates the evaluation result of a feature gate for a specific user. It's mostly about getting metadata about the gate.

Properties​

  • name ( String ): name of the feature gate.

  • value ( Boolean ): Indicates the feature gate's status for the user.

  • ruleID ( String? ): The identifier of the rule applied to determine the feature gate's status. It can be null if the evaluation falls back to a default status or if no specific rule was matched.

  • secondaryExposures ( ArrayList<Map<String, String>> ): A collection of secondary exposures encountered during the feature gate's evaluation.

  • reason ( EvaluationReason? ): The reason behind the feature gate's evaluation result.

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.

Note that while typing is lenient on the StatsigUser object to allow you to pass in numbers, strings, arrays, objects, and potentially even enums or classes, the evaluation operators will only be able to operate on primitive types - mostly strings and numbers. While we attempt to smartly cast custom field types to match the operator, we cannot guarantee evaluation results for other types. For example, setting an array as a custom field will only ever be compared as a string - there is no operator to match a value in that array.

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 pass in an optional parameter options in addition to the server secret during initialization to customize the Statsig client. Here are the current options and we are always adding more to the list:

  • initTimeoutMs: double, default 3000
    • used to decide how long the Statsig client waits for the initial network request to respond before calling the completion block. The Statsig client will return either cached values (if any) or default values if checkGate/getConfig/getExperiment is called before the initial network request completes.
    • if you always want to wait for the latest values fetched from Statsig server, you should set this to 0 so we do not timeout the network request.
    • unit is milliseconds.
  • environment tier: string, default null
    • used to signal the environment tier the user is currently in
    • e.g. passing in a value of "staging" will allow your users to pass any condition that pass for the staging environment tier, and fail any condition that only passes for other environment tiers.
    • example:
val options = StatsigOptions()
options.setTier("staging")

  • bootstrapValues: string?, default null

    • a string that represents all rules for all feature gates, dynamic configs and experiments. It can be provided to bootstrap the Statsig server SDK at initialization in case your server runs into network issue or Statsig server is down temporarily.

  • rulesUpdatedCallback: ((rules: String) -> Unit)?, default null

    • a callback function that's called whenever we have an update for the rules; it's called with a JSON string (used as is for bootstrapValues mentioned above) and a timestamp.

  • localMode - boolean, default false

    • Pass true to this option to turn on Local Mode for the SDK, which will stop the SDK from issuing any network requests and make it only operate with only local overrides (If supported) and cache.
      Note: Since no network requests will be made, a dummy SDK key starting with "secret-" can be used. (eg "secret-key")

  • api - String?, default null

    • The API endpoint to use for initialization and logging. Default to STATSIG_API_URL_BASE

  • rulesetsSyncIntervalMs - Long, default 10 * 1000

  • idListsSyncIntervalMs - Long, default 60 * 1000

  • dataStore

  • userPersistentStorage: IUserPersistentStorage default nil

  • customLogger - LoggerInterface

  • disableAllLogging - Boolean, default false

  • proxyConfig - ProxyConfig

      /**
      * Represents configuration for a proxy.
      *
      * @property proxyHost The hostname or IP address of the proxy server.
      * @property proxyPort The port number of the proxy server.
      * @property proxyAuth Optional: Authentication credentials for the proxy server. 
      *                     Pass in `Credentials.basic("username", "password")`.
      * @property proxySchema The protocol scheme used by the proxy server. Defaults to "https".
      */
      data class ProxyConfig @JvmOverloads constructor(
          var proxyHost: String,
          var proxyPort: Int,
          var proxyAuth: String? = null,
          val proxySchema: String = "https"
      )

    Example Usage


      import okhttp3.Credentials;

      // Create a ProxyConfig object With Auth
      ProxyConfig proxyConfigWithAuth = new ProxyConfig("localhost", 8080, Credentials.basic("username", "password"), "https");

      // Create a ProxyConfig object Without Auth
      ProxyConfig proxyConfig = new ProxyConfig("localhost", 8080);

      StatsigOptions options = new StatsigOptions();
      options.setProxyConfig(proxyConfig);
      Future initFuture = Statsig.initializeAsync(apiKey, options);
      initFuture.get();

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.shutdown();

Client SDK Bootstrapping | SSR v1.4.1+​

The Java/Kotlin server SDK, starting in 1.4.1 supports generating the initializeValues needed to bootstrap a Statsig Client SDK preventing a round trip to Statsig servers. This can also be used with web [ @statsig/js-client, @statsig/react-bindings] SDKs to perform server side rendering (SSR).

Available in v1.4.1+


StatsigUser user = new StatsigUser("user_id");
Map<String, Object> initializeValues = driver.getClientInitializeResponse(user);

// pass initializeValues to a client SDK to initialize without a network request

Working with IP or UserAgent Values​

This will not automatically use the ip, or userAgent for gate evaluation as Statsig servers would, since there is no request from the client SDK specifying these values. If you want to use conditions like IP, or conditions which are inferred from the IP/UA like: Browser Name or Version, OS Name or Version, Country, you must manually set the ip and userAgent field on the user object when calling getClientInitializeResponse.

Working with stableID​

There is no auto-generated stableID for device based experimentation, since the server generates the initialize response without any information from the client SDK. If you wish to run a device based experiment while using the server to generate the initialize response, we recommend you:

  1. Create a customID in the Statsig console. See experimenting on custom IDs for more information.
  2. Generate an ID on the server, and set it in a cookie to be used on the client side as well.
  3. Set that ID as the customID on the StatsigUser object when generating the initialize response from the SDK.
  4. Get that ID from the cookie, and set it as the customID on the StatsigUser object when using the client SDK, so all event data and exposure checks tie back to the same user.

Alternatively, if you wish to use the stableID field rather than a custom ID, you still need to do step (2) above. Then:

  • Override the stableID in the client SDK by getting the value from the cookie and setting the overrideStableID parameter in StatsigOptions
  • Set the stableID field on the StatsigUser object in the customIDs map when generating the initialize response from the SDK

Local Overrides ​

If you want to locally override gates/configs/experiments/layers, there are a set of override APIs as follows. Coupling this with StatsigOptions.localMode can be useful when writing unit tests.

// Overrides the given gate to the specified value
Statsig.overrideGate("a_gate_name", true);

// Overrides the given config (dynamic config or experiment) to the provided value
Statsig.overrideConfig("a_config_or_experiment_name", Map.of("key", "value"));

// Overrides the given layer to the provided value
Statsig.overrideLayer("a_layer_name", Map.of("key", "value"));

// Removing gate overrides
Statsig.removeGateOverride("a_gate_name");

// Removing config/experiment overrides
Statsig.removeConfigOverride("a_config_or_experiment_name");

// Removing layer overrides
Statsig.removeLayerOverride("a_layer_name");
note
  1. These only apply locally - they do not update definitions in the Statsig console or elsewhere.
  2. The local override API is not designed to be a full mock. They are only a convenient way to override the value of the gate/config/etc.

User Persistent Storage​

A custom storage adapter that allows the SDK the persist values for users in active experiments. In other words, allowing you to run experiments with sticky bucketing. You can provide a persistent storage adapter via StatsigOptions.UserPersistentStorage.

You can read more about the concept here.

Storage Interface​

You can write you own custom storage that implements the following interface:

typealias UserPersistedValues = Map<String, StickyValues>

interface IUserPersistentStorage {
    /**
     * Returns the full map of persisted values for a specific user key
     * @param key user key
     */
    suspend fun load(key: String): UserPersistedValues

    /**
     * Save the persisted values of a config given a specific user key
     * @param key user key
     * @param configName Name of the config/experiment
     * @param data Object representing the persistent assignment to store for the given user-config
     */
    fun save(key: String, configName: String, data: StickyValues)

    /**
     * Delete the persisted values of a config given a specific user key
     * @param key user key
     * @param configName Name of the config/experiment
     */
    fun delete(key: String, configName: String)
}

Example Implementation​

class KongUserPersistedStorageAdapter() : IUserPersistentStorage {
    private var value: MutableMap<String, UserPersistedValues> = mutableMapOf()

    override suspend fun load(key: String): UserPersistedValues {
        return value[key] ?: mapOf()
    }

    override fun save(key: String, experimentName: String, data: StickyValues) {
        val userPersistedValue = (value[key] ?: mutableMapOf()) as MutableMap<String, StickyValues>
        userPersistedValue[experimentName] = data
        value[key] = userPersistedValue
    }

    override fun delete(key: String, experiment: String) {
        value.remove(key)
    }
}

Multiple Statsig SDK Instances​

Our documentation up to this point guides you through setting up your Statsig integration via the singleton Statsig.

There are cases where you may need to create multiple instances of the Statsig SDK. Each SDK supports this as well - the Statsig singleton wraps a single instance of the SDK that you can instantiate. NOTE: currently all sdk instances will use the same keys when interacting with a Data Store/Data Adapter. You will not be able to isolate multiple instances of the sdk in your data store.

All top level static methods from the singleton carry over as instance methods. To create an instance of the Statsig sdk:

StatsigServer sdkInstance = new StatsigServer();
Future initFuture = sdkInstance.initializeAsync(serverSecret, options);
initFuture.get();

Proxy Configurations v1.24.0+​

Advance SDK Network setup, provide options to configure network protocol and proxy address for individual network endpoint. This option is provided for better integration with Statsig Forward Proxy

Authentication v1.30.0+​

With more advanced requirements on security, we also support TLS and mTLS for grpc streaming (protocol=GRPC_WEBSOCKET) You need to configure ProxyConfig for each endpoint

authentication_mode: TLS, mTLS, disabled // default is disabled
tlsPrivateKeyPassword // Input stream to client certification 
tlsPrivateKey // Input stream to client key password
tlsCertChain  // Input stream to root TLS certificate

Installation

We are still in the testing phase of this feature. Package deployment / installation will be different.

To install the Beta SDK Version with Forward Proxy Support, you will need to install a separate test project

repositories {
    mavenCentral()
}

Then add the dependency:

implementation 'com.statsig:serversdk-test:0.24.0' // 0.24.0 is the only version with proxy config support

If you are using shadowJar, include below lines in your build file

tasks.named<com.github.jengelman.gradle.plugins.shadow.tasks.ShadowJar>("shadowJar") {
    mergeServiceFiles()
}

Initialization

To setup grpc streaming for download config spec. And use default behavior for get_id_lists and log_events endpoints.

  String address = "0.0.0.0:50051";
  Map<NetworkEndpoint, ForwardProxyConfig> proxyConfigs = new HashMap();
  proxyConfigs.put(NetworkEndpoint.DOWNLOAD_CONFIG_SPECS, new ForwardProxyConfig(address, NetworkProtocol.GRPC_WEBSOCKET));
  StatsigOptions options = new StatsigOptions();
  options.setEndpointProxyConfigs(proxyConfigs);
  Statsig.initializeAsync(secret_key, options).join();

FAQ​

How do I run experiments for logged out users?​

See the guide on device level experiments

How can I mock Statsig for testing?​

First, there is a StatsigOptions parameter called localMode. Setting localMode to true will cause the SDK to never hit the network, and only return default values. This is perfect for dummy environments or test environments that should not access the network.

Next, there are the overrideGate and overrideConfig APIs on the global Statsig interface, see Local Overrides.

These can be used to set a gate or config value to be be returned for the given name.

We suggest you enable localMode and then override gates/configs to specific values to test the various code flows you are building.

You can view LocalOverridesTest to see overrides being used in test.

How can I bootstrap an on-device evaluation sdk?​

If you are using a client on-device evaluation SDK, it consumes the same payload as Statsig server SDKs to do local evaluation.

The Java Server SDK v1.31.0+ exposes this payload via:

getOnDeviceEvalInitializeResponse(clientSDKKey: String? = null): Map<String, Any>

The method returns a map which is the JSON payload that a client SDK will need to initialize synchronously.

You can use the clientSDKKey parameter to get the initialize response for a specific client key. This enables you to use Target Apps to filter down the list of gates/configs/experiments/layers accessible by that client key. If not specified, the entire payload the server is operating with will be returned.

You can then use the synchronous initialization method on the client SDK to initialize with this payload.

Reference​

StatsigUser​

/**
 * An object of properties relating to the current user
 * Provide as many as possible to take advantage of advanced conditions in the Statsig console
 * A dictionary of additional fields can be provided under the "custom" field
 * @property userID - string - REQUIRED - a unique identifier for the user.  Why is this required?  See https://docs.statsig.com/messages/serverRequiredUserID/
 * @property email - string - an email associated with the current user
 * @property ip - string - the ip address of the requests for the user
 * @property userAgent - string - the user agent of the requests for this user
 * @property country - string - the two letter country code of the user
 * @property locale - string - the locale for the user
 * @property appVersion - string -  the current version of the app
 * @property custom - Map<string, string> - any additional custom user attributes for custom conditions in the console
 * @property privateAttributes - Map<string, Object> - any user attributes that should be used in evaluation only and removed in any logs.
 * @property customIDs - Map<string, string> - Map of ID name to ID value for custom identifiers
 */
data class StatsigUser

StatsigOptions and StatsigEnvironment​

private const val TIER_KEY: String = "tier"
private const val DEFAULT_API_URL_BASE: String = "https://statsigapi.net/v1"
private const val DEFAULT_INIT_TIME_OUT_MS: Long = 3000L
private const val CONFIG_SYNC_INTERVAL_MS: Long = 10 * 1000
private const val ID_LISTS_SYNC_INTERVAL_MS: Long = 60 * 1000


/**
 * A SAM for Java compatibility
 */
@FunctionalInterface
fun interface RulesUpdatedCallback {
    fun accept(rules: String)
}

enum class Tier {
    PRODUCTION,
    STAGING,
    DEVELOPMENT,
}

class StatsigOptions(
    var api: String = DEFAULT_API_URL_BASE,
    var initTimeoutMs: Long? = DEFAULT_INIT_TIME_OUT_MS,
    var bootstrapValues: String? = null,
    var rulesUpdatedCallback: RulesUpdatedCallback? = null,
    var localMode: Boolean = false,
    var rulesetsSyncIntervalMs: Long = CONFIG_SYNC_INTERVAL_MS,
    var idListsSyncIntervalMs: Long = ID_LISTS_SYNC_INTERVAL_MS,
    var dataStore: IDataStore? = null,
    var customLogger: LoggerInterface = defaultLogger,
    var disableAllLogging: Boolean = false,
) {

    // to set the environment tier
    fun setTier(tier : Tier);
}

DataStore​

abstract class IDataStore {
    abstract fun get(key: String): String?
    abstract fun set(key: String, value: String)
    abstract fun shutdown()
}

LoggerInterface​

interface LoggerInterface {
    fun warning(message: String)
    fun info(message: String)
}

val defaultLogger = object : LoggerInterface {

    override fun warning(message: String) {
        println(message)
    }

    override fun info(message: String) {
        println(message)
    }
}