kalix.scalasdk.action.Action.scala Maven / Gradle / Ivy
/*
* Copyright 2021 Lightbend Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package kalix.scalasdk.action
import scala.concurrent.ExecutionContext
import scala.concurrent.Future
import kalix.scalasdk.{ DeferredCall, Metadata, SideEffect }
import kalix.scalasdk.impl.action.ActionEffectImpl
import io.grpc.Status
import kalix.javasdk.impl.action.ActionContextImpl
import kalix.scalasdk.impl.action.ScalaActionContextAdapter
import kalix.scalasdk.timer.TimerScheduler
import kalix.scalasdk.impl.timer.TimerSchedulerImpl
object Action {
/**
* An Effect is a description of what Kalix needs to do after the command is handled. You can think of it as a set of
* instructions you are passing to Kalix. Kalix will process the instructions on your behalf.
*
* Each Kalix component defines its own effects, which are a set of predefined operations that match the capabilities
* of that component.
*
* An Action Effect can either:
*
* - reply with a message to the caller
* - reply with a message to be published to a topic (in case the method is a publisher)
* - forward the message to another component
* - return an error
* - ignore the call
*
* A return type to allow returning forwards or failures, and attaching effects to messages. A return type to allow
* returning forwards or failures, and attaching effects to messages.
*
* @tparam T
* The type of the message that must be returned by this call.
*/
trait Effect[+T] {
/**
* Attach the given side effects to this reply.
*
* @param sideEffects
* The effects to attach.
* @return
* A new reply with the attached effects.
*/
def addSideEffect(sideEffects: SideEffect*): Action.Effect[T]
def addSideEffects(sideEffects: Seq[SideEffect]): Action.Effect[T]
/**
* @return
* true if this effect supports attaching side effects, if returning false addSideEffects will throw an exception.
*/
def canHaveSideEffects: Boolean
}
/**
* Construct the effect that is returned by the command handler. The effect describes next processing actions, such as
* sending a reply.
*/
object Effect {
trait Builder {
/**
* Create a message reply.
*
* @param message
* The payload of the reply.
* @return
* A message reply.
* @tparam S
* The type of the message that must be returned by this call.
*/
def reply[S](message: S): Action.Effect[S]
/**
* Create a message reply.
*
* @param message
* The payload of the reply.
* @param metadata
* The metadata for the message.
* @return
* A message reply.
* @tparam S
* The type of the message that must be returned by this call.
*/
def reply[S](message: S, metadata: Metadata): Action.Effect[S]
/**
* Create a forward reply.
*
* @param serviceCall
* The service call representing the forward.
* @return
* A forward reply.
* @tparam S
* The type of the message that must be returned by this call.
*/
def forward[S](serviceCall: DeferredCall[_, S]): Action.Effect[S]
/**
* Create an error reply.
*
* @param description
* The description of the error.
* @return
* An error reply.
* @tparam S
* The type of the message that must be returned by this call.
*/
def error[S](description: String): Action.Effect[S]
/**
* Create an error reply.
*
* @param description
* The description of the error.
* @param statusCode
* A gRPC status code.
* @return
* An error reply.
* @tparam S
* The type of the message that must be returned by this call.
*/
def error[S](description: String, statusCode: Status.Code): Action.Effect[S]
/**
* Create a message reply from an async operation result.
*
* @param message
* The future payload of the reply.
* @return
* A message reply.
* @tparam S
* The type of the message that must be returned by this call.
*/
def asyncReply[S](message: Future[S]): Action.Effect[S]
/**
* Create a reply from an async operation result returning an effect.
*
* @param futureEffect
* The future effect to reply with.
* @return
* A reply, the actual type depends on the nested Effect.
* @tparam S
* The type of the message that must be returned by this call.
*/
def asyncEffect[S](futureEffect: Future[Action.Effect[S]]): Action.Effect[S]
/**
* Ignore the current element and proceed with processing the next element if returned for an element from
* eventing in. If used as a response to a regular gRPC or HTTP request it is turned into a NotFound response.
*
* Ignore is not allowed to have side effects added with `addSideEffects`
*/
def ignore[S]: Action.Effect[S]
}
}
}
/**
* Actions are stateless components that can be used to implement different uses cases, such as:
*
* - a pure function.
* - request conversion - you can use Actions to convert incoming data into a different format before forwarding a
* call to a different component.
* - publish messages to a Topic.
* - subscribe to events from an Event Sourced Entity.
* - subscribe to state changes from a Value Entity.
* - schedule and cancel Timers.
*
* Actions can be triggered in multiple ways. For example, by:
*
* - a gRPC service call.
* - an HTTP service call.
* - a forwarded call from another component.
* - a scheduled call from a Timer.
* - an incoming message from a Topic.
* - an incoming event from an Event Sourced Entity, from within the same service or from a different service.
* - state changes notification from a Value Entity on the same service.
*
* An Action method should return an [[kalix.scalasdk.action.Action.Effect]] that describes what to do next.
*/
abstract class Action {
@volatile
private var _actionContext: Option[ActionContext] = None
/**
* An ExecutionContext to use when composing Futures inside Actions.
*/
implicit def executionContext: ExecutionContext =
scala.concurrent.ExecutionContext.Implicits.global
/**
* Additional context and metadata for a message handler.
*
* It will throw an exception if accessed from constructor.
*/
protected final def actionContext: ActionContext =
actionContext("ActionContext is only available when handling a message.")
/**
* INTERNAL API
*
* Same as actionContext, but if specific error message when accessing components.
*/
protected final def contextForComponents: ActionContext =
actionContext("Components can only be accessed when handling a message.")
private def actionContext(errorMessage: String): ActionContext =
_actionContext.getOrElse(throw new IllegalStateException(errorMessage))
/** INTERNAL API */
final def _internalSetActionContext(context: Option[ActionContext]): Unit = {
_actionContext = context
}
/**
* Returns a [[TimerScheduler]] that can be used to schedule further in time.
*/
final def timers: TimerScheduler = {
val javaActionContextImpl =
actionContext("Timers can only be scheduled or cancelled when handling a message.") match {
case ScalaActionContextAdapter(actionContext: ActionContextImpl) => actionContext
// should not happen as we always need to pass ScalaActionContextAdapter(ActionContextImpl)
case other =>
throw new RuntimeException(
s"Incompatible ActionContext instance. Found ${other.getClass}, expecting ${classOf[ActionContextImpl].getName}")
}
new TimerSchedulerImpl(javaActionContextImpl.messageCodec, javaActionContextImpl.system)
}
protected final def effects[T]: Action.Effect.Builder =
ActionEffectImpl.builder()
}