Migration from Apache Pekko 1.x to 2.x

Apache Pekko 2.x is not Binary Compatible with Apache Pekko 1.x.

The major difference is that some deprecated code has been removed but there are also a small number of breaking changes where deprecation was not feasible.

It is possible that some simple code compiled with Pekko 1.x libs will work with Pekko 2.x but you should not rely on this.

Pekko 1.x is still maintained and major bugs will be fixed in it.

Start by upgrading to latest Pekko 1.x releases

Some of the changes in Pekko 2.x have been backported although these changes are normally only done when they fix important bugs.

Some additional code has been deprecated in the most recent 1.x releases and the compile warnings will help you with moving onto better supported APIs.

Change any code that relies on deprecated APIs in Pekko 1.x

Not every deprecated API has been removed in Pekko 2.x but many have been.

Java API users may find that they have more deprecations to deal with because the Scala API is more stable and there were a few mistakes in the Java API where Scala classes leaked into some of the Java API methods.

Additional Breaking Changes in Pekko 2.x

An example is in the Scala DSL for Flow and Source, the watchTermination function call no longer needs an empty param list before a second param list. Instead of watchTermination(){ ... }, you now must use watchTermination{ ... }. (PR2378)

In the Java API, FSMTransitionHandlerBuilder.build and FSMTransitionHandlerBuilder.state now use pekko.japi.Pair instead of scala.Tuple2. Java users need to update their code to use Pair instead of Tuple2. (PR3378)

The Java DSL SourceWithContext graph shape now uses pekko.japi.Pair instead of scala.Tuple2. Java code that passes a SourceWithContext directly to GraphDSL must use Pair-typed stages. Code that converts it with asSource() already uses Pair and requires no changes. (PR3388)

ReceiveTimeout changed from a case object singleton to a final case class that carries the configured timeout duration. Scala pattern matches must use a type pattern (case timeout: ReceiveTimeout =>) instead of a stable identifier pattern, and the ReceiveTimeout.getInstance() method has been removed from the Java API; Java users should match on ReceiveTimeout.class instead. (PR3399)