Dear hAkkers,
we—the Akka committers—proudly present the first development milestone for Akka 2.4. Since the release of Akka 2.3.0 (already 14.5 months ago) much has happened, in particular around Streams & HTTP. It may therefore surprise you that these additions to the Akka toolkit are not yet part of the 2.4 development branch, but if you read on for a little while the pieces of the puzzle will fall into place. Besides a plethora of small improvements the main changes relative to the 2.3.x series are:
- we dropped support for Java 6 & 7 as announced in the last roadmap update, requiring now Java 8 or later
- we dropped support for Scala 2.10, kept 2.11 and added 2.12 (which is at milestone 1 currently as well); this is in keeping with our policy to support the Scala version that is “current” when the first milestone comes out plus any later version that is published during this series’ lifetime
- we added the experimental Akka Typed module previously codenamed Project Gålbma, a new way of formulating Actor interactions with full type-system support
- we promoted the ClusterSingleton, ClusterClient, DistributedPubSub and ClusterSharding patterns to fully supported Cluster tools
- ClusterSharding also learnt a few new tricks (asynchronous shard allocation, reviving entries after migration [thanks to Dominic Black], and more flexible use of roles [thanks to Richard Marscher])
- Akka Persistence can now use multiple different Journals within one ActorSystem (thanks to Andrei Pozolotin, who also split out ClusterMetrics into their own module)
- we also removed the default Journal plugin and removed the hard dependency on LevelDB (since that was not a recommended production configuration anyway)
- we added support for binding to a different host & port than what the ActorSystem advertises to its peers, a.k.a. “allow Akka to run in Docker containers”
- the SLF4J logging adapter can now apply the log filtering rules prior to sending to the EventStream, see the migration guide
- but the biggest feature is probably that Akka 2.4 will be binary backwards compatible with Akka 2.3, see the detailed description below.
Being binary compatible means that applications and libraries built on top of Akka 2.3.x continue to work with Akka 2.4.x without recompilation (subject to the conditions below), which implies that Akka Streams & HTTP as well as the upcoming Play Framework 2.4 can be combined with Akka 2.4.
Akka 2.4 Roadmap
What remains to be done before we can release 2.4.0-RC1 is to
- complete the Java API and the documentation for Akka Typed
- finalize Akka Persistence on the Write Side (i.e. PersistentActor will be non-experimental; the work on the Read Side will be deferred until Akka 2.5)
- incorporate Streams & HTTP once ready (to become an experimental module, as usual)
- incorporate Patrik’s akka-data-replication under the new module name akka-distributed-data
We will perform this work within the next weeks, releasing further milestones when appropriate. Please do what you usually do so well: try out our latest and report back when things break, not work as advertised, feel strange, or even when you are happy :-) Especially concerning binary compatibility we will need help from the community (you!) since we cannot run all possible programs ourselves; we base our BC efforts on the MiMa plugin but that is no perfect guarantee that everything will work out of the box.
Binary Compatibility
Akka 2.4.x is backwards binary compatible with previous 2.3.x versions (exceptions listed below). This means that the new JARs are a drop-in replacement for the old one (but not the other way around) as long as your build does not enable the inliner (Scala-only restriction). It should be noted that Scala 2.11.x is is not binary compatible with Scala 2.10.x, which means that Akka’s binary compatibility property only holds between versions that were built for a given Scala version—akka-actor_2.11-2.4-M1.jar is compatible with akka-actor_2.11-2.3.11.jar but not with akka-actor_2.10-2.3.11.jar.
Binary compatibility is not maintained for the following:
- akka-testkit and akka-multi-node-testkit
- experimental modules, such as akka-persistence and akka-contrib
- features, classes, methods that were deprecated in 2.3.x and removed in 2.4.x
The dependency to Netty has been updated from version 3.8.0.Final to 3.10.3.Final. The changes in those versions might not be fully binary compatible, but we believe that it will not be a problem in practice. No changes were needed to the Akka source code for this update. Users of libraries that depend on 3.8.0.Final that break with 3.10.3.Final should be able to manually downgrade the dependency to 3.8.0.Final and Akka will still work with that version.
The dependency to Typesafe Config has been updated from 1.2.1 to 1.3.0 which should be binary compatible for the vast majority users, except for obscure edge cases as its changelog points out. This change was made in order in order to use new JDK8 specific features in the library as well as to align Akka with Play which is now also depending on 1.3.0.
When migrating a code base to 2.4 please refer to the migration guide in order to profit from some of the improvements.
Additional Release Details
The artifacts comprising this release have been published to https://repo1.maven.org/maven2/ and also to Maven Central. In addition, we adopted the sbt standard of encoding the Scala binary version in the artifact name, i.e. the core actor package’s artifactId is “akka-actor_2.11” or “akka-actor_2.12.0-M1”, respectively.
The complete list of closed tickets can be found in the 2.4-M1 github issues milestone.
Credits
We are extraordinarily proud of the long list of contributors to this release, looking at the commit history we find more than 100 names! We are particularly thankful to hepin1989 (a.k.a. kerr) who contributed already 19 pull requests to Akka. Other noteworthy mentions besides Andrei Pozolotin’s, Dominic Black’s and Richard Marscher’s (which are already listed above) are:
- Improve remote watching mechanism by Thibaut Robert
- Improve AtLeastOnceDelivery by Adam Warski
- Get current topics in DistributedPubSub by Ben Poserow
2.3.0 compared to 2.4-M1:
commits added removed
140 17263 28182 Patrik Nordwall
64 9394 2486 Konrad 'ktoso' Malawski
36 6444 3433 Roland Kuhn
33 3686 734 Björn Antonssonn
27 2300 1275 Martynas Mickevičius
11 345 179 hepin
8 10253 620 Andrei Pozolotin
8 1254 136 Endre Sándor Varga
8 768 255 Viktor Klang
6 28 15 Nitsan Wakart
4 5 5 Stanislav Savulchik
3 89 14 Csongor Somogyi
3 4 4 kerr
3 58 16 Johannes Rudolph
3 90 7 Benjamin Poserow
3 144 8 Colin Godsey
3 101 65 Eugene Platonov
3 140 94 Marcin Kubala
3 128 8 Nikita Melkozerov
3 60 9 kustosz
2 110 14 Jeroen Gordijn
2 127 8 Balázs Kossovics
2 5 3 Stevo Slavić
2 916 188 Dominic Black
2 869 834 dario.rexin
2 10 9 xuwei-k
2 218 192 Thibaut Robert
2 181 68 Tomasz Lelek
1 10 2 Saeed Zarinfam
1 4 6 gfaerie
1 2 1 Kane Rogers
1 2 2 Chris Johnson
1 42 20 rmarsch
1 1 1 Richard Summerhayes
1 8 3 Mathias
1 15 15 Ben McCann
1 1 1 Piyush Mishra
1 2 2 Valerian
1 1 1 Jonas Fonseca
1 3 3 Michael Ummels
1 1 1 Katherine Fellows
1 15 1 Ahmed Soliman
1 36 39 Paweł Kaczor
1 71 1 Brendan Lawlor
1 41 18 Ostapenko Evgeniy
1 2 2 André Wolski
1 2 2 Katsunori Kanda
1 53 37 Michal Knapik
1 605 0 Martin Krasser
1 284 8 dch
1 2 2 Arnaud Gourlay
1 246 2 Michal Rus
1 440 34 Giovanni Botta
1 74 15 Martin Eigenbrodt
1 2 2 Shikhar Bhushan
1 103 29 Michael R. Maletich
1 2 2 Seulgi Kim
1 1 1 Heiko Seeberger
1 246 28 Michał Węgrzyn
1 2 2 Pavel Boldyrev
1 1 1 Goddamned Qu
1 2 2 Dale Wijnand
1 6 6 Evan Tsue
1 1 1 Raymond Roestenburg
1 219 37 Xingrun CHEN
1 439 17 Ilya Epifanov
1 1 1 Dawid Malina
1 53 7 dormidon
1 0 7 Samuel Heaney
1 78 12 adamw
1 2 2 Ruurtjan
1 630 26 Krzysztof Janosz
1 12 2 Paul Roman
1 45 0 Dan Brown
1 1 1 litomSegal
1 8 2 Gaju Bhat
1 197 121 rasummer
1 42 3 Alejandro Lujan
1 25 2 Ekin Gecikligun
1 2 3 Eric Le Goff
1 8 6 Raul Bache
1 17 10 sangche
1 394 0 Gaston M. Tonietti
1 768 768 Julian Tescher
1 7 0 John Ulric
1 1 1 Flavio W. Brasil
1 414 0 Dario Rexin
1 1 1 Duarte Nunes
1 1 1 qian miao
1 2 2 Tair Sabirgaliev
1 95 18 Łukasz Dubiel
1 44 11 Marek Prochera
1 446 0 Marcus Ljungblad
1 2 2 Sergey Kisel
1 6 1 Reid Spencer
1 5 5 nordicway
1 8 7 Pavel Zalunin
1 1 1 Ronak Buch
1 4 4 drozzy
1 1 1 Jacob Gulotta
1 1 1 LeonardMeyer
1 2 1 Arnout Engelen
1 1 1 Chris Grieger
1 8 46 Sergey Krauchenia
1 55 6 Paweł Wiejacha
1 37 15 Max Cai
Happy hAkking!