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Using a custom HTTP client

By default, uses the following HTTP clients for different platforms/languages:

PlatformHTTP Client
JavaScript/Wasmfetch() / Node Fetch for HTTP, Ktor for WebSockets

Implement your own HTTP engine

You can use a different HTTP client with Apollo Kotlin by creating a custom class that implements the HttpEngine interface.

The HttpEngine interface defines two functions: execute and close. Here's an example implementation that also includes a couple of helper methods:

class MyHttpEngine(val wrappedClient: MyClient) : HttpEngine {
* Helper function to map the Apollo requests to MyClient requests
private fun HttpMethod.toMyClientRequest(): MyClientRequest {
* And the other way around
private fun MyClientResponse.toApolloResponse(): HttpResponse {
override suspend fun execute(request: HttpRequest) = suspendCancellableCoroutine { continuation ->
val call = wrappedClient.newCall(request.toMyClientRequest())
continuation.invokeOnCancellation {
// If the coroutine is cancelled, also cancel the HTTP call
success = { myResponse ->
// Success! report the response
error = { throwable ->
// Error. Wrap in an ApolloException and report the error
override fun close() {
// Dispose any resources here

This example uses an asynchronous wrappedClient that runs the network request in a separate thread. Note that because HttpEngine.execute itself is called from a background thread, you can safely block in execute().

Using your HttpEngine

After you create your HttpEngine implementation, you can register it with your ApolloClient instance using ApolloClient.Builder.httpEngine:

// Use your HttpEngine
val client = ApolloClient.Builder()
.serverUrl(serverUrl = "")
.httpEngine(httpEngine = MyHttpEngine(wrappedClient))

With this configuration, Apollo Kotlin sends all of its requests with MyHttpEngine.

Ktor engine

An implementation of HttpEngine based on Ktor is available in apollographql/apollo-kotlin-ktor-support

Other HTTP customizations

Besides implementing HttpEngine, Apollo Kotlin also supports other methods for customizing HTTP behavior:

  • No runtime: You can opt out of the Apollo Kotlin runtime completely and only use generated models and parsers. Use this option if you don't need any of the runtime features (caching, batching, , etc.).
  • HTTP interceptors: If you want to add HTTP headers and/or logging to your requests, HTTP interceptors enable you to do this with minimal code.
Using the models without apollo-runtime
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