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Pekko-Scala-3-Upgrade-Notes.md

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Notes on changes made to move from akka to pekko and scala-2.13.8 to 3.3.0

Changes made to switch from akka to pekko

Updated dependencies

  • Replaced akka dependencies with pekko dependencies:
  • Used these sbt resolvers:
    resolvers += "Apache Pekko Staging".at("https://repository.apache.org/content/groups/staging"),
    resolvers += "jitpack" at "https://jitpack.io",
akka dependency pekko dependency
akka-management-cluster-http pekko-management
akka-stream-kafka pekko-connectors-kafka
borer-compat-akka borer-compat-pekko
akka-http-spray-json Not needed, included
akka-http pekko-http
akka-actor pekko-actor
akka-stream pekko-stream
etc... etc...
  • Replaced akka with pekko everywhere (preserve case)
  • Renamed files: *akka* to *pekko* and *Akka* to *Pekko*
  • Replaced import pekko. with import org.apache.pekko.
  • Replaced remaining "pekko.: in source and conf files with org.apache.pekko (Care needed config files, since class refs use org.apache.pekko, but settings use just pekko)
  • Replaced dependencies on any TMT libraries that depend on akka
  • For msocket, for now using jitpack with unreleased branch allan/migrate-akka-to-pekko-scala3
  • For embedded-keycloak, for now using jitpack with unreleased branch migrate-to-pekko-scala3
  • For rtm (TMT Test reporters) now using scala3 branch via jitpack
  • For csw-docs (generate documentation) no using branch "Allan/scala3", updated dependencies, replaced akka with org.apache.pekko
  • Updated keycloak API usage to match newer version (Note: TODO: Still using older version)
  • Needed to add explicit dependency on pekko-stream when using pekko-http

Changes made to upgrade from Scala-2.13.8 to Scala-3.3.0

  • Updated all dependencies
  • Updated to use scala3 syntax for imports (._ replaced with .*)
  • Added parens around lambda arguments as required by scala3
  • Removed scala-java8-compat
  • Replaced
import scala.compat.java8.FunctionConverters.enrichAsScalaFromConsumer
import scala.compat.java8.FutureConverters.FutureOps
import scala.jdk.CollectionConverters._

with

import scala.jdk.FunctionConverters.*
import scala.jdk.FutureConverters.*
import scala.jdk.CollectionConverters.*

And changed uses of toScala, toJava, asScala, asJava as needed.

Use different dependency for async/await

  • Replaced scala-async dependency with dotty-cps-async
  • Replaced scala.async import with import cps.compat.FutureAsync.*
  • Replaced some implicits with given. For example:
  implicit class RichFuture[T](val f: Future[T]) extends AnyVal{...}

was replaced with

  class RichFuture[T](val f: Future[T]) extends AnyVal {...}

  given futureConversion[T]: Conversion[Future[T], RichFuture[T]] with
    def apply(x: Future[T]): RichFuture[T] = RichFuture(x)
  • Replaced imports of implicits with given import:
import csw.alarm.cli.utils.TestFutureExt.RichFuture

was replaced with

import csw.alarm.cli.utils.TestFutureExt.given
import scala.language.implicitConversions
  • Added some Scala methods to support JSON serialization from Java, since the CBOR library uses inline macros, which can't be accessed directly from Java
  • Removed lazy or added final to some actorSystem and other definitions in various Wiring classes, since in Scala 3 you can't import non-final lazy vals (i.e.: import Wiring.*)
  • Replaced some inherited lazy vals with defs due to new Scala 3 restrictions.
  • Replaced code like this:
sealed trait Command { self: ParameterSetType[_] => 

  def paramType: ParameterSetType[_] = self

with this:

sealed trait Command extends ParameterSetType[Command] {

  def paramType: ParameterSetType[_] = this

due to Scala3 complaints.

  • When initializing Array[Double], you now have to actually use doubles (1.0, 2.0) and not ints (1, 2)

  • Commented out one CBOR test for Java, since it is not likely to be used from Java.

  • Replaced use of App class in some cases with Scala main() as recommended for Scala 3

  • Removed (probably unnecessary) call to redisReactiveCommands.getStatefulConnection.close(), since it was deprecated

  • Commented out tests using embedded-kafka due to unknown errors (The Kafka based Event Service is not currently being used).