Kotlin (JVM) - GrowthBook Documentation

This SDK supports Kotlin and Java backend applications running on the JVM, including server applications, CLI tools, and worker processes. It’s optimized for server-side usage with suspend-first APIs and production-safe defaults.

Android Development?If you’re building Android applications, see the Kotlin (Android) documentation instead, which includes Android-specific guidance for Gradle Android plugin, Android engines, and AARs.

Supported Platforms

JVM: Java 8+ and Kotlin 1.5+
Server Applications: Ktor, Spring Boot, Micronaut, Quarkus
CLI Tools: Command-line applications and scripts
Worker Processes: Background jobs and data processing
Microservices: Containerized applications and serverless functions

Installation

Add the GrowthBook JVM SDK and a network dispatcher to your project:

dependencies {
    implementation("io.growthbook.sdk:GrowthBook-jvm:7.1.0")

    // Choose ONE network dispatcher (JVM-safe):
    implementation("io.growthbook.sdk:NetworkDispatcherOkHttp-jvm:1.0.7") // Recommended for servers
    // OR
    implementation("io.growthbook.sdk:NetworkDispatcherKtor-jvm:1.0.12")  // If using Ktor CIO

    // Optional: JSON serialization helpers
    implementation("io.growthbook.sdk:GrowthBookKotlinxSerialization-jvm:1.0.0")
}

dependencies {
    implementation 'io.growthbook.sdk:GrowthBook-jvm:7.1.0'

    // Choose ONE network dispatcher (JVM-safe):
    implementation 'io.growthbook.sdk:NetworkDispatcherOkHttp-jvm:1.0.7' // Recommended for servers
    // OR
    implementation 'io.growthbook.sdk:NetworkDispatcherKtor-jvm:1.0.12'  // If using Ktor CIO

    // Optional: JSON serialization helpers
    implementation 'io.growthbook.sdk:GrowthBookKotlinxSerialization-jvm:1.0.0'
}

<dependencies>
    <dependency>
        <groupId>io.growthbook.sdk</groupId>
        <artifactId>GrowthBook-jvm</artifactId>
        <version>7.1.0</version>
    </dependency>

    {/* Choose ONE network dispatcher (JVM-safe): */}
    <dependency>
        <groupId>io.growthbook.sdk</groupId>
        <artifactId>NetworkDispatcherOkHttp-jvm</artifactId>
        <version>1.0.7</version>
    </dependency>
    {/* OR */}
    <dependency>
        <groupId>io.growthbook.sdk</groupId>
        <artifactId>NetworkDispatcherKtor-jvm</artifactId>
        <version>1.0.12</version>
    </dependency>

    {/* Optional: JSON serialization helpers */}
    <dependency>
        <groupId>io.growthbook.sdk</groupId>
        <artifactId>GrowthBookKotlinxSerialization-jvm</artifactId>
        <version>1.0.0</version>
    </dependency>
</dependencies>

Important: Use JVM-specific ArtifactsAlways use the -jvm variants of the artifacts for server applications. Do not include Android artifacts or the Ktor Android engine, as they will add unnecessary dependencies and increase your application size.

Quick Start

Here’s a minimal example to get started with the GrowthBook Kotlin JVM SDK:

import com.sdk.growthbook.GBSDKBuilder
import com.sdk.growthbook.model.GBExperiment
import com.sdk.growthbook.model.toGbString
import com.sdk.growthbook.network.GBNetworkDispatcherOkHttp

suspend fun main() {
    // User attributes for targeting and experiments
    val attributes = mapOf(
        "id" to "user_123".toGbString(),
        "environment" to "production".toGbString(),
        "organization" to "acme-corp".toGbString(),
        "role" to "admin".toGbString()
    )

    // Create network dispatcher (OkHttp recommended for servers)
    val networkDispatcher = GBNetworkDispatcherOkHttp()

    // Build GrowthBook SDK instance
    val growthBook = GBSDKBuilder(
        apiKey = "sdk_abc123",
        apiHost = "https://cdn.growthbook.io/",
        attributes = attributes,
        networkDispatcher = networkDispatcher,
        trackingCallback = { experiment, result ->
            // Track experiment views in your analytics
            println("Experiment: ${experiment.key}, Variation: ${result.variationId}")
        }
    ).initialize()

    // Fetch feature definitions
    growthBook.refreshCache()

    // Evaluate feature flags
    val newFeatureEnabled = growthBook.feature("new-checkout-flow").on
    val maxRetries = growthBook.featureValue<Int>("max-retries") ?: 3

    println("New checkout flow: $newFeatureEnabled")
    println("Max retries: $maxRetries")

    // Run inline experiments
    val buttonColorExperiment = growthBook.run(
        GBExperiment(
            key = "button-color-test",
            variations = listOf("blue", "red", "green").map { it.toGbString() }
        )
    )

    println("Button color: ${buttonColorExperiment.value}")
}

Network Dispatchers

The GrowthBook SDK requires a network dispatcher for fetching feature definitions. Choose the appropriate one for your use case:

OkHttp Dispatcher (Recommended)

Best for most server applications due to its smaller dependency footprint:

import com.sdk.growthbook.network.GBNetworkDispatcherOkHttp

val networkDispatcher = GBNetworkDispatcherOkHttp(
    // Optional configuration
    client = customOkHttpClient, // Use your existing OkHttp client
    enableLogging = false,       // Enable SDK-level request logging
    maxRetries = 10,             // Max SSE reconnection retries
    initialRetryDelayMs = 1_000L,
    maxRetryDelayMs = 30_000L
)

Ktor CIO Dispatcher

Use this if you’re already using Ktor in your application:

import com.sdk.growthbook.network.GBNetworkDispatcherKtor
import io.ktor.client.HttpClient
import io.ktor.client.engine.cio.*

val networkDispatcher = GBNetworkDispatcherKtor(
    // Optional: supply a pre-configured Ktor HttpClient (CIO engine required for JVM)
    client = HttpClient(CIO) {
        // configure Ktor plugins here if needed
    },
    enableLogging = false,
    maxRetries = 10,
    initialRetryDelayMs = 1_000L,
    maxRetryDelayMs = 30_000L
)

Avoid Android EnginesWhen using Ktor, always specify the CIO engine explicitly. Do not use the Android engine in server applications as it will add unnecessary dependencies.

Configuration

Configure the GrowthBook SDK for your server environment:

val growthBook = GBSDKBuilder(
    // Required
    apiKey = "sdk_abc123",
    apiHost = "https://cdn.growthbook.io/",
    attributes = userAttributes,
    networkDispatcher = networkDispatcher,

    // Optional configuration
    trackingCallback = { experiment, result ->
        // Your analytics tracking
        analyticsService.track("experiment_viewed", mapOf(
            "experiment_id" to experiment.key,
            "variation_id" to result.variationId,
            "user_id" to userAttributes["id"]
        ))
    },

    // Enable local caching (enabled by default)
    cachingEnabled = true,

    // Enable debug logging to stdout
    enableLogging = false
)
    // Disable randomization for QA testing
    .setQAMode(false)
    // Callback fired when features are refreshed from the server
    .setRefreshHandler { success, error ->
        if (success) {
            logger.info("Features refreshed successfully")
        } else {
            logger.error("Feature refresh failed: ${error?.errorMessage}")
        }
    }
    .initialize()

Evaluating Features and Running Experiments

Feature Flags

Evaluate feature flags to control application behavior:

// Simple boolean feature
val newFeatureEnabled = growthBook.feature("new-checkout-flow").on
if (newFeatureEnabled) {
    // Show new checkout flow
    showNewCheckoutFlow()
} else {
    // Show legacy checkout
    showLegacyCheckout()
}

// Feature with default value
val maxRetries = growthBook.featureValue<Int>("max-retries") ?: 3
val timeout = growthBook.featureValue<Long>("api-timeout") ?: 5000L

// Complex feature values
val config = growthBook.feature("service-config").gbValue as? GBJson
val enabledServices = (config?.get("enabled") as? GBArray)
    ?.mapNotNull { (it as? GBString)?.value }
    ?: emptyList()

Feature Evaluation with Context

Update user attributes for different contexts:

// Evaluate for different users
growthBook.setAttributes(mapOf(
    "id" to "user_123".toGbString(),
    "plan" to "premium".toGbString(),
    "country" to "US".toGbString()
))
val premiumFeature = growthBook.feature("premium-dashboard").on

// Switch to different user context
growthBook.setAttributes(mapOf(
    "id" to "user_456".toGbString(),
    "plan" to "free".toGbString(),
    "country" to "CA".toGbString()
))
val freeUserFeature = growthBook.feature("premium-dashboard").on // Will be different

Running Experiments

Run A/B tests and experiments directly:

// Simple A/B test
val experiment = GBExperiment(
    key = "button-color-test",
    variations = listOf("blue", "red", "green").map { it.toGbString() }
).apply {
    weights = listOf(0.33f, 0.33f, 0.34f)
}

val result = growthBook.run(experiment)
val buttonColor = result.value
val inExperiment = result.inExperiment

if (inExperiment) {
    println("User is in experiment, showing $buttonColor button")
    setButtonColor(buttonColor)
} else {
    println("User not in experiment, using default")
    setButtonColor("blue") // default
}

// Complex experiment with targeting
val pricingExperiment = GBExperiment(
    key = "pricing-test",
    variations = listOf(9.99, 14.99, 19.99).map { it.toGbNumber() }
).apply {
    weights = listOf(0.5f, 0.3f, 0.2f)
    condition = JsonObject(mapOf(
        "country" to JsonPrimitive("US"),
        "plan" to JsonPrimitive("premium")
    ))
}

val pricingResult = growthBook.run(pricingExperiment)
if (pricingResult.inExperiment) {
    val price = pricingResult.value as GBNumber
    displayPrice(price)
}

Experiment Tracking

Track experiment exposures for analytics:

val growthBook = GBSDKBuilder(
    // ... other config
    trackingCallback = { experiment, result ->
        // Send to your analytics platform
        analytics.track("experiment_viewed", mapOf(
            "experiment_id" to experiment.key,
            "variation_id" to result.variationId,
            "variation_value" to result.value,
            "user_id" to attributes["id"],
            "in_experiment" to result.inExperiment
        ))

        println("Tracked: ${experiment.key} -> ${result.value}")
    }
).initialize()

Advanced Features

For more advanced usage including sticky bucketing, encrypted features, custom attributes, and mobile-specific considerations, see the Kotlin (Android) documentation which covers these topics in detail.

Serialization Support

The optional serialization module provides helpers for working with GBValue and kotlinx.serialization:

import com.sdk.growthbook.serialization.*

@Serializable
data class FeatureConfig(
    val maxRetries: Int,
    val timeout: Long,
    val enabledFeatures: List<String>
)

// Convert GBValue to typed objects
val configValue = growthBook.feature("service-config").gbValue
val config: FeatureConfig? = configValue.decodeAs<FeatureConfig>()

// Use the configuration
config?.let {
    println("Max retries: ${it.maxRetries}")
    println("Timeout: ${it.timeout}")
}

When to Use SerializationYou only need the serialization module if you want to work with complex JSON feature values as typed Kotlin objects. For simple boolean, string, and number features, you can skip this dependency.

Caching and Server-Sent Events

Caching

The builder exposes a cachingEnabled flag. On JVM, fetched features remain in the SDK instance after refresh, but there is no platform-provided persistent local cache layer:

val growthBook = GBSDKBuilder(
    apiKey = "sdk_abc123",
    apiHost = "https://cdn.growthbook.io/",
    attributes = attributes,
    networkDispatcher = networkDispatcher,
    trackingCallback = { _, _ -> },
    cachingEnabled = true // true by default
).initialize()

// Manually re-fetch and cache the latest features at any time
growthBook.refreshCache()

To be notified when features are refreshed, use setRefreshHandler() on the builder:

val builder = GBSDKBuilder(
    apiKey = "sdk_abc123",
    apiHost = "https://cdn.growthbook.io/",
    attributes = attributes,
    networkDispatcher = networkDispatcher,
    trackingCallback = { _, _ -> }
)
builder.setRefreshHandler { success, error ->
    if (success) {
        logger.info("Features refreshed successfully")
    } else {
        logger.warn("Feature refresh failed: ${error?.errorMessage}")
    }
}
val growthBook = builder.initialize()

Real-time Updates with SSE

Start a persistent Server-Sent Events connection for live feature updates:

val growthBook = GBSDKBuilder(
    apiKey = "sdk_abc123",
    apiHost = "https://cdn.growthbook.io/",
    streamingHost = "https://cdn.growthbook.io/", // SSE endpoint host
    attributes = attributes,
    networkDispatcher = networkDispatcher,
    trackingCallback = { _, _ -> }
).initialize()

// Collect the SSE flow in a coroutine scope
val flow = growthBook.startAutoRefreshFeatures()
flow.launchIn(coroutineScope)

// Stop the SSE connection when no longer needed
growthBook.stopAutoRefreshFeatures()

Error Handling and Observability

Exception Handling

The SDK uses suspend functions and handles errors gracefully:

try {
    growthBook.refreshCache()
} catch (e: Exception) {
    logger.error("Failed to refresh features", e)
    // Use setRefreshHandler() to observe refresh success/failure callbacks
}

Logging Integration

The SDK outputs debug information to stdout when enableLogging is set to true. You can capture this in your application by redirecting stdout to your logging framework:

val growthBook = GBSDKBuilder(
    apiKey = "sdk_abc123",
    apiHost = "https://cdn.growthbook.io/",
    attributes = attributes,
    networkDispatcher = networkDispatcher,
    trackingCallback = { _, _ -> },
    enableLogging = true // prints debug info to stdout
).initialize()

Testing

Mock Dispatchers

Use mock dispatchers for unit testing:

import com.sdk.growthbook.network.NetworkDispatcher
import com.sdk.growthbook.utils.Resource
import com.sdk.growthbook.utils.SSEConnectionController
import kotlinx.coroutines.Job
import kotlinx.coroutines.flow.Flow
import kotlinx.coroutines.flow.emptyFlow

class MockNetworkDispatcher : NetworkDispatcher {
    var mockFeatures: String = """{"features": {}}"""

    override fun consumeGETRequest(
        request: String,
        onSuccess: (String) -> Unit,
        onError: (Throwable) -> Unit
    ): Job {
        onSuccess(mockFeatures)
        return Job()
    }

    override fun consumeSSEConnection(
        url: String,
        sseController: SSEConnectionController?
    ): Flow<Resource<String>> = emptyFlow()

    override fun consumePOSTRequest(
        url: String,
        bodyParams: Map<String, Any>,
        onSuccess: (String) -> Unit,
        onError: (Throwable) -> Unit
    ) {}
}

// In your tests
@Test
fun testFeatureEvaluation() = runTest {
    val mockDispatcher = MockNetworkDispatcher()
    mockDispatcher.mockFeatures = """
        {
            "features": {
                "test-feature": {
                    "defaultValue": true,
                    "rules": []
                }
            }
        }
    """.trimIndent()

    val growthBook = GBSDKBuilder(
        apiKey = "test",
        apiHost = "http://localhost",
        attributes = mapOf("id" to "test-user".toGbString()),
        networkDispatcher = mockDispatcher,
        trackingCallback = { _, _ -> }
    ).initialize()

    growthBook.refreshCache()

    assertTrue(growthBook.feature("test-feature").on)
}

Deterministic Testing

Use local JSON fixtures for predictable tests:

@Test
fun testExperimentVariations() = runTest {
    val testFeatures = loadResourceAsString("/test-features.json")

    val mockDispatcher = MockNetworkDispatcher()
    mockDispatcher.mockFeatures = testFeatures

    val growthBook = GBSDKBuilder(
        apiKey = "test",
        apiHost = "http://localhost",
        attributes = mapOf("id" to "user_123".toGbString()), // Deterministic user
        networkDispatcher = mockDispatcher,
        trackingCallback = { _, _ -> }
    ).initialize()

    growthBook.refreshCache()

    // Test will always get the same variation for user_123
    val result = growthBook.run(
        GBExperiment(
            key = "button-color-test",
            variations = listOf("blue", "red").map { it.toGbString() }
        )
    )

    assertEquals("blue", (result.value as GBString).value) // Deterministic based on user ID
}

Performance and Resource Usage

Connection Pooling

Configure connection pooling for high-throughput applications:

val customOkHttpClient = OkHttpClient.Builder()
    .connectionPool(ConnectionPool(10, 5, TimeUnit.MINUTES))
    .connectTimeout(10, TimeUnit.SECONDS)
    .readTimeout(30, TimeUnit.SECONDS)
    .writeTimeout(10, TimeUnit.SECONDS)
    .build()

val networkDispatcher = GBNetworkDispatcherOkHttp(client = customOkHttpClient)

Coroutine Dispatchers

Use appropriate dispatchers for different workloads:

import kotlinx.coroutines.Dispatchers
import kotlinx.coroutines.withContext

// For CPU-intensive feature evaluation
val result = withContext(Dispatchers.Default) {
    growthBook.feature("complex-feature").on
}

// For network operations (handled internally by SDK)
val refreshed = withContext(Dispatchers.IO) {
    growthBook.refreshCache()
}

Avoid Blocking Calls

Never use runBlocking on request threads in server applications:

// ❌ DON'T: Blocks the request thread
fun handleRequest(request: HttpRequest): HttpResponse {
    val feature = runBlocking {
        growthBook.feature("new-feature").on
    }
    // ...
}

// ✅ DO: Use suspend functions end-to-end
suspend fun handleRequest(request: HttpRequest): HttpResponse {
    val feature = growthBook.feature("new-feature").on
    // ...
}

Framework Integration Examples

Ktor Server

import io.ktor.server.application.*
import io.ktor.server.engine.*
import io.ktor.server.netty.*
import io.ktor.server.response.*
import io.ktor.server.routing.*

fun main() {
    embeddedServer(Netty, port = 8080) {
        // Initialize GrowthBook as singleton
        val growthBook = GBSDKBuilder(
            apiKey = System.getenv("GROWTHBOOK_API_KEY"),
            apiHost = "https://cdn.growthbook.io/",
            attributes = mapOf("environment" to "production".toGbString()),
            networkDispatcher = GBNetworkDispatcherKtor(),
            trackingCallback = { _, _ -> }
        ).initialize()

        // Refresh features on startup
        launch {
            growthBook.refreshCache()
        }

        routing {
            get("/api/features/{userId}") {
                val userId = call.parameters["userId"] ?: return@get call.respond(400)

                // Create user-specific attributes
                val userAttributes = mapOf(
                    "id" to userId.toGbString(),
                    "environment" to "production".toGbString()
                )

                // Update attributes for this request
                growthBook.setAttributes(userAttributes)

                // Evaluate features
                val features = mapOf(
                    "newDashboard" to growthBook.feature("new-dashboard").on,
                    "maxItems" to growthBook.featureValue<Int>("max-items"),
                    "theme" to growthBook.featureValue<String>("theme")
                )

                call.respond(features)
            }
        }
    }.start(wait = true)
}

Spring Boot

import org.springframework.boot.autoconfigure.SpringBootApplication
import org.springframework.boot.runApplication
import org.springframework.context.annotation.Bean
import org.springframework.context.annotation.Configuration
import org.springframework.web.bind.annotation.*

@SpringBootApplication
class Application

@Configuration
class GrowthBookConfig {

    @Bean
    suspend fun growthBook(): GrowthBookSDK {
        val growthBook = GBSDKBuilder(
            apiKey = System.getenv("GROWTHBOOK_API_KEY"),
            apiHost = "https://cdn.growthbook.io/",
            attributes = mapOf("environment" to "production".toGbString()),
            networkDispatcher = GBNetworkDispatcherOkHttp(),
            trackingCallback = { _, _ -> }
        ).initialize()

        growthBook.refreshCache()
        return growthBook
    }
}

@RestController
@RequestMapping("/api")
class FeatureController(private val growthBook: GrowthBookSDK) {

    @GetMapping("/features/{userId}")
    suspend fun getUserFeatures(@PathVariable userId: String): Map<String, Any?> {
        // Set user-specific attributes
        growthBook.setAttributes(mapOf(
            "id" to userId.toGbString(),
            "environment" to "production".toGbString()
        ))

        return mapOf(
            "newDashboard" to growthBook.feature("new-dashboard").on,
            "maxItems" to growthBook.featureValue<Int>("max-items"),
            "premiumFeatures" to growthBook.feature("premium-features").on
        )
    }

    @PostMapping("/experiments/{userId}")
    suspend fun runExperiment(
        @PathVariable userId: String,
        @RequestParam experimentKey: String
    ): Map<String, Any?> {
        growthBook.setAttributes(mapOf("id" to userId.toGbString()))

        val result = growthBook.run(
            GBExperiment(
                key = experimentKey,
                variations = listOf("control", "treatment").map { it.toGbString() }
            )
        )

        return mapOf(
            "variation" to result.value,
            "inExperiment" to result.inExperiment,
            "variationId" to result.variationId
        )
    }
}

fun main(args: Array<String>) {
    runApplication<Application>(*args)
}

CLI Application

import kotlinx.coroutines.runBlocking

fun main(args: Array<String>) = runBlocking {
    val userId = args.getOrNull(0) ?: "cli-user"

    // Initialize GrowthBook for CLI usage
    val growthBook = GBSDKBuilder(
        apiKey = System.getenv("GROWTHBOOK_API_KEY") ?: "sdk_dev_key",
        apiHost = "https://cdn.growthbook.io/",
        attributes = mapOf(
            "id" to userId.toGbString(),
            "environment" to "cli".toGbString(),
            "version" to "1.0.0".toGbString()
        ),
        networkDispatcher = GBNetworkDispatcherOkHttp(),
        trackingCallback = { _, _ -> }
    ).initialize()

    try {
        // Fetch latest features
        println("Fetching feature definitions...")
        growthBook.refreshCache()

        // Evaluate features for CLI behavior
        val verboseLogging = growthBook.feature("verbose-logging").on
        val maxConcurrency = growthBook.featureValue<Int>("max-concurrency") ?: 1
        val outputFormat = growthBook.featureValue<String>("output-format") ?: "json"

        println("Configuration:")
        println("  Verbose logging: $verboseLogging")
        println("  Max concurrency: $maxConcurrency")
        println("  Output format: $outputFormat")

        // Run your CLI logic here
        performCliTask(verboseLogging, maxConcurrency, outputFormat)

    } catch (e: Exception) {
        println("Error: ${e.message}")
        kotlin.system.exitProcess(1)
    }
}

suspend fun performCliTask(verbose: Boolean, concurrency: Int, format: String) {
    // Your CLI implementation
    if (verbose) {
        println("Running with verbose logging enabled")
    }
    println("Processing with concurrency level: $concurrency")
    println("Output format: $format")
}

Versioning and Compatibility

Module Versions

GrowthBook Kotlin JVM modules follow independent versioning:

Module	Latest Version	Purpose
`GrowthBook-jvm`	7.1.0	Core SDK
`NetworkDispatcherOkHttp-jvm`	1.0.7	OkHttp networking
`NetworkDispatcherKtor-jvm`	1.0.12	Ktor CIO networking
`GrowthBookKotlinxSerialization-jvm`	1.0.0	JSON serialization

Compatibility Matrix

SDK Version	Min Kotlin	Min JDK	OkHttp Dispatcher	Ktor Dispatcher
7.1.x	1.5.0	Java 8	1.0.7+	1.0.12+
5.x.x	1.4.0	Java 8	1.0.1+	1.0.5+

Dependency Management

Pin JVM-specific versions explicitly in monorepos:

// build.gradle.kts
dependencies {
    // Explicitly specify JVM variants
    implementation("io.growthbook.sdk:GrowthBook-jvm:7.1.0")
    implementation("io.growthbook.sdk:NetworkDispatcherOkHttp-jvm:1.0.7")

    // Avoid mixing Android and JVM artifacts
    // ❌ Don't do this in server projects:
    // implementation("io.growthbook.sdk:GrowthBook:1.1.60") // Android variant
}

Migration from Android Documentation

If you started with the Android documentation but need server-side usage:

Key Differences

Aspect	Android	JVM (Server)
Artifacts	`io.growthbook.sdk:GrowthBook:7.1.0`	`io.growthbook.sdk:GrowthBook-jvm:7.1.0`
Network	Android engines OK	Use CIO or OkHttp only
Threading	Main thread considerations	Suspend-first, no runBlocking
Lifecycle	Activity/Fragment tied	Long-running singleton
Caching	Persistent storage	No persistent local cache layer

Migration Steps

Update Dependencies: Replace Android artifacts with JVM variants
Remove Android Engines: Use OkHttp or Ktor CIO only
Update Network Dispatcher: Ensure JVM-compatible engines
Review Threading: Remove runBlocking from request handlers
Update Caching: Configure appropriate TTL for server usage

Troubleshooting

Common Issues

Problem: ClassNotFoundException for Android classes

Solution: Ensure you're using -jvm artifacts, not Android variants

Problem: Large JAR size in server deployments

Solution: Use OkHttp dispatcher instead of Ktor with Android engine

Problem: Blocking network calls in request handlers

Solution: Use suspend functions end-to-end, avoid runBlocking

Problem: Features not updating in long-running processes

Solution: Enable SSE or implement periodic cache refresh

Debug Logging

Enable debug logging to troubleshoot issues. The SDK prints to stdout when enableLogging = true:

val growthBook = GBSDKBuilder(
    apiKey = "sdk_abc123",
    apiHost = "https://cdn.growthbook.io/",
    attributes = attributes,
    networkDispatcher = networkDispatcher,
    trackingCallback = { _, _ -> },
    enableLogging = true
).initialize()

​Supported Platforms

​Installation

​Quick Start

​Network Dispatchers

​OkHttp Dispatcher (Recommended)

​Ktor CIO Dispatcher

​Configuration

​Evaluating Features and Running Experiments

​Feature Flags

​Feature Evaluation with Context

​Running Experiments

​Experiment Tracking

​Advanced Features

​Serialization Support

​Caching and Server-Sent Events

​Caching

​Real-time Updates with SSE

​Error Handling and Observability

​Exception Handling

​Logging Integration

​Testing

​Mock Dispatchers

​Deterministic Testing

​Performance and Resource Usage

​Connection Pooling

​Coroutine Dispatchers

​Avoid Blocking Calls

​Framework Integration Examples

​Ktor Server

​Spring Boot

​CLI Application

​Versioning and Compatibility

​Module Versions

​Compatibility Matrix

​Dependency Management

​Migration from Android Documentation

​Key Differences

​Migration Steps

​Troubleshooting

​Common Issues

​Debug Logging

​Supported Features

​Further Reading

Supported Platforms

Installation

Quick Start

Network Dispatchers

OkHttp Dispatcher (Recommended)

Ktor CIO Dispatcher

Configuration

Evaluating Features and Running Experiments

Feature Flags

Feature Evaluation with Context

Running Experiments

Experiment Tracking

Advanced Features

Serialization Support

Caching and Server-Sent Events

Caching

Real-time Updates with SSE

Error Handling and Observability

Exception Handling

Logging Integration

Testing

Mock Dispatchers

Deterministic Testing

Performance and Resource Usage

Connection Pooling

Coroutine Dispatchers

Avoid Blocking Calls

Framework Integration Examples

Ktor Server

Spring Boot

CLI Application

Versioning and Compatibility

Module Versions

Compatibility Matrix

Dependency Management

Migration from Android Documentation

Key Differences

Migration Steps

Troubleshooting

Common Issues

Debug Logging

Supported Features

Further Reading