In Memory Pub/Sub Engine using Akka Actors and Streams.
Latest Version: 0.1.9
"io.github.d-exclaimation" %% "subpub" % latestVersionSubPub main goals are to:
- Handle creation, distribution, management of both the outgoing stream of data and incoming published data.
- Differentiate streams based on topic, which can used to push the proper data into the proper streams.
- Also handles creation in a lazy and concurrent safe way, no need to worry about race conditions.
- All of the above on lightweight code embedded implementation.
Similar to PubSub from graphql-subscriptions, SubPub is also
an in-memory event streaming system that only supports a single server instance. On a production environment, it is
strongly recommended to use other implementation that are backed with an external datastore such as Redis or Kafka.
Consider using Alpakka instead for this scenario.
REST + Websocket Realtime API
An example using this for HTTP + Websocket Realtime API
import io.github.dexclaimation.subpub.SubPub
object Main extends SprayJsonSupport {
// ...
val pubsub = SubPub()
val route: Route = {
(path("send" / Segment) & post & entity(as[JsValue])) { path =>
entity(as[JsValue]) {
case JsObject(body) => sendMessage(path, body)
case _ => complete(BadRequest -> JsString("Bad message"))
}
} ~ path("websocket" / Segment) { path =>
handleWebSocketMessages(websocketMessage(path))
}
}
// Handle HTTP Post and emit to websocket
def sendMessage(path: String, body: Map[String, JsValue]): Route = {
try {
val content = body("content")
val name = body("name")
val msg = JsObject(
"content" -> content,
"name" -> name,
"createdAt" -> JsString(Instant.now().toString)
)
// Push message to subpub
pubsub.publish(s"chat::$path", msg)
complete(OK -> msg)
} catch {
case NonFatal(_) =>
complete(BadRequest -> "Bad message")
}
}
// Handle Websocket Flow using the topic based Source
def websocketMessage(path: String): Flow[Message, TextMessage.Strict, _] = {
val source = pubsub
.source[JsValue](s"chat::$path")
.map(_.compactPrint)
.map(TextMessage.Strict)
val sink = Flow[Message]
.map(_ => ()) // On Websocket Message
.to(Sink.onComplete(_ => ())) // on Websocket End
Flow.fromSinkAndSource(sink, source)
}
// ...
}Realtime GraphQL API
Using with a Realtime GraphQL API with Subscription using Sangria and OverLayer.
import io.github.dexclaimation.subpub.SubPub
object Main {
// ...
val MessageType = ???
val (roomArg, stringArg, nameArg) = ???
val QueryType = ???
val MutationType = ObjectType(
"Mutation",
fields[SubPub, Unit](
// GraphQL Mutation to send message
Field("send", MessageType,
arguments = roomArg :: stringArg :: nameArg :: Nil,
resolve = { c =>
val msg = Message(c arg stringArg, c arg nameArg, Instant.now().toString)
// Publish data into subscription
c.ctx.publish[Message](c arg roomArg, msg)
msg
}
)
)
)
val SubscriptionType = ObjectType(
"Subscription",
field[SubPub, Unit](
// GraphQL Subscription to get realtime data stream
Field.subs("room", MessageType,
arguments = roomArg :: Nil,
// Use the Source from SubPub and map it to Action for Sangria
resolve = c => c.ctx.source[Message](c arg roomArg).map(Action(_))
)
)
)
val schema = Schema(QueryType, Some(MutationType), Some(SubscriptionType))
// OverLayer for handling GraphQL over Websocket
val gqlTransport = OverTransportLayer(schema, ())
val pubsub = SubPub()
val route: Route =
path("graphql" / "websocket") {
gqlTransport.applyMiddleware(pubsub)
}
}If you have any feedback, please reach out to me through the issues tab or Twitter @d_exclaimation
