Scalaz backend

The Scalaz backend is asynchronous. Sending a request is a non-blocking, lazily-evaluated operation and results in a response wrapped in a scalaz.concurrent.Task. There’s a transitive dependency on scalaz-concurrent.

Using async-http-client

To use, add the following dependency to your project:

"com.softwaremill.sttp.client3" %% "async-http-client-backend-scalaz" % "3.8.1"

This backend depends on async-http-client and uses Netty behind the scenes.

Next you’ll need to add an implicit value:

import sttp.client3._
import sttp.client3.asynchttpclient.scalaz.AsyncHttpClientScalazBackend

AsyncHttpClientScalazBackend().flatMap { backend => ??? }

// or, if you'd like to use custom configuration:
import org.asynchttpclient.AsyncHttpClientConfig
val config: AsyncHttpClientConfig = ???

AsyncHttpClientScalazBackend.usingConfig(config).flatMap { backend => ??? }

// or, if you'd like to use adjust the configuration sttp creates:
import org.asynchttpclient.DefaultAsyncHttpClientConfig
val sttpOptions: SttpBackendOptions = SttpBackendOptions.Default  
val adjustFunction: DefaultAsyncHttpClientConfig.Builder => DefaultAsyncHttpClientConfig.Builder = ???

AsyncHttpClientScalazBackend.usingConfigBuilder(adjustFunction, sttpOptions).flatMap { backend => ??? }

// or, if you'd like to instantiate the AsyncHttpClient yourself:
import org.asynchttpclient.AsyncHttpClient
val asyncHttpClient: AsyncHttpClient = ???

val backend = AsyncHttpClientScalazBackend.usingClient(asyncHttpClient)

Using Armeria

To use, add the following dependency to your project:

"com.softwaremill.sttp.client3" %% "armeria-backend-scalaz" % "3.8.1"

add imports:

import sttp.client3.armeria.scalaz.ArmeriaScalazBackend

create client:

val backend = ArmeriaScalazBackend()

// You can use the default client which reuses the connection pool of ClientFactory.ofDefault()

or, if you’d like to instantiate the WebClient yourself:

import com.linecorp.armeria.client.circuitbreaker._
import com.linecorp.armeria.client.WebClient

// Fluently build Armeria WebClient with built-in decorators
val client = WebClient.builder("")
             // Open circuit on 5xx server error status

val backend = ArmeriaScalazBackend.usingClient(client)


A WebClient could fail to follow redirects if the WebClient is created with a base URI and a redirect location is a different URI.

This backend is build on top of Armeria. Armeria’s ClientFactory manages connections and protocol-specific properties. Please visit the official documentation to learn how to configure it.


This backend doesn’t support non-blocking streaming.


The backend doesn’t support websockets.