Scopes

Scopes are namespaces for Streams, they must be created before being referenced (no automatic creation).

import io.pravega.client.ClientConfig

import zio._
import zio.pravega._
import zio.pravega.admin._


val aScopeUIO: RIO[PravegaStreamManager,Boolean] =
   PravegaStreamManager.createScope("sales")

The aScopeUIO is a RIO[PravegaStreamManager,Boolean] that:

• will produce true if the scope was created or false if it already existed.
• depends on the PravegaStreamManager capability.

This is a common pattern in ZIO applications, where the capability is provided by the environment and the result is a ZIO value that can be composed with other ZIO values.

To provide the capability we need to create a PravegaStreamManager to this effect, which is the role of ZLayer:

val manager: RLayer[Scope & ClientConfig, PravegaStreamManager] =
                           PravegaStreamManager.live

This ZLayer in turn depends on Scope and ClientConfig capabilities, which are provided by another layers, and ZIO this will combile all these layers:

val createScope: Task[Boolean] =
    aScopeUIO
      .provide(
        Scope.default,
        PravegaClientConfig.live,
        PravegaStreamManager.live
      )

By producing a Task[Unit] value, then a runnable IO.