Monix backends
There are several backend implementations which are monix.eval.Task
-based. These backends are asynchronous. Sending a request is a non-blocking, lazily-evaluated operation and results in a response wrapped in a Task
.
Using HttpClient
Creation of the backend can be done in two basic ways:
by creating a
Task
, which describes how the backend is created, or instantiating the backend directly. In this case, you’ll need to close the backend manually.by creating a
Resource
, which will instantiate the backend and close it after it has been used.
Firstly, add the following dependency to your project:
"com.softwaremill.sttp.client3" %% "monix" % "3.10.1"
and create the backend using:
import sttp.client3.httpclient.monix.HttpClientMonixBackend
HttpClientMonixBackend().flatMap { backend => ??? }
// or, if you'd like the backend to be wrapped in cats-effect Resource:
HttpClientMonixBackend.resource().use { backend => ??? }
// or, if you'd like to instantiate the HttpClient yourself:
import java.net.http.HttpClient
val httpClient: HttpClient = ???
val backend = HttpClientMonixBackend.usingClient(httpClient)
// or, obtain a cats-effect Resource with a custom instance of the HttpClient:
import java.net.http.HttpClient
val httpClient: HttpClient = ???
HttpClientMonixBackend.resourceUsingClient(httpClient).use { backend => ??? }
This backend is based on the built-in java.net.http.HttpClient
available from Java 11 onwards.
Host header override is supported in environments running Java 12 onwards, but it has to be enabled by system property:
-Djdk.httpclient.allowRestrictedHeaders=host
Using OkHttp
To use, add the following dependency to your project:
"com.softwaremill.sttp.client3" %% "okhttp-backend-monix" % "3.10.1"
Create the backend using:
import sttp.client3.okhttp.monix.OkHttpMonixBackend
OkHttpMonixBackend().flatMap { backend => ??? }
// or, if you'd like the backend to be wrapped in cats-effect Resource:
OkHttpMonixBackend.resource().use { backend => ??? }
// or, if you'd like to instantiate the OkHttpClient yourself:
import okhttp3._
val okHttpClient: OkHttpClient = ???
val backend = OkHttpMonixBackend.usingClient(okHttpClient)
This backend depends on OkHttp and fully supports HTTP/2.
Using Armeria
To use, add the following dependency to your project:
"com.softwaremill.sttp.client3" %% "armeria-backend-monix" % "3.10.1"
add imports:
import sttp.client3.armeria.monix.ArmeriaMonixBackend
create client:
import monix.execution.Scheduler.Implicits.global
val backend = ArmeriaMonixBackend()
// You can use the default client which reuses the connection pool of ClientFactory.ofDefault()
ArmeriaMonixBackend.usingDefaultClient()
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("https://my-service.com")
// Open circuit on 5xx server error status
.decorator(CircuitBreakerClient.newDecorator(CircuitBreaker.ofDefaultName(),
CircuitBreakerRule.onServerErrorStatus()))
.build()
val backend = ArmeriaMonixBackend.usingClient(client)
Note
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.
Streaming
The Monix backends support streaming. The streams capability is represented as sttp.client3.impl.monix.MonixStreams
. The type of supported streams in this case is Observable[ByteBuffer]
. That is, you can set such an observable as a request body (using the http-client backend as an example, but any of the above backends can be used):
import sttp.capabilities.monix.MonixStreams
import sttp.client3._
import sttp.client3.httpclient.monix.HttpClientMonixBackend
import monix.reactive.Observable
HttpClientMonixBackend().flatMap { backend =>
val obs: Observable[Array[Byte]] = ???
basicRequest
.streamBody(MonixStreams)(obs)
.post(uri"...")
.send(backend)
}
And receive responses as an observable stream:
import sttp.capabilities.monix.MonixStreams
import sttp.client3._
import sttp.client3.httpclient.monix.HttpClientMonixBackend
import monix.eval.Task
import monix.reactive.Observable
import scala.concurrent.duration.Duration
HttpClientMonixBackend().flatMap { backend =>
val response: Task[Response[Either[String, Observable[Array[Byte]]]]] =
basicRequest
.post(uri"...")
.response(asStreamUnsafe(MonixStreams))
.readTimeout(Duration.Inf)
.send(backend)
response
}
Websockets
The Monix backend supports both regular and streaming websockets.
Server-sent events
Received data streams can be parsed to a stream of server-sent events (SSE):
import monix.reactive.Observable
import monix.eval.Task
import sttp.capabilities.monix.MonixStreams
import sttp.client3.impl.monix.MonixServerSentEvents
import sttp.model.sse.ServerSentEvent
import sttp.client3._
def processEvents(source: Observable[ServerSentEvent]): Task[Unit] = ???
basicRequest.response(asStream(MonixStreams)(stream =>
processEvents(stream.transform(MonixServerSentEvents.parse))))