Dear hakkers,

We are excited to announce a new patch release of Akka 2.6. Notable changes relative to 2.6.9 include:

• Improvements of rolling updates and rebalance in Cluster Sharding, see below
• Quick dissemination of downing decisions, #29612
• Log message sizes in Artery, #29683
• Configurable stream restart deadline, thanks to @r-glyde, #29291
• Config for when to move to WeaklyUp, #29665
• Deliver Terminated after ordinary messages in Artery, #28695
• Support async reply in EventSourcedBehaviorTestKit, #29602
• Update Aeron to 1.30.0

As well as some important bug fixes:

• Proper threadsafe collection of stream snapshots, #28960
• Use correct heartbeat-interval for cross-dc failure detection, #29614

2.6.10 includes 53 closed issues. The complete list can be found on the 2.6.10 milestone on github.

Sharding improvements

Akka 2.6.10 includes several improvements of Cluster Sharding for better rolling updates and a new faster rebalance algorithm.

To make rolling updates as smooth as possible there is a configuration property that defines the version of the application. This is used by rolling update features to distinguish between old and new nodes, and avoid allocation to old nodes during a rolling update. See the documentation for how to enable this feature.

There is also a new health check for Cluster Sharding that you can enable when you don’t want to receive production traffic until the local shard region is ready to retrieve locations for shards.

The new rebalance algorithm can reach optimal balance in a few rebalance rounds (typically 1 or 2 rounds). You can still configure limits of how many shards to move in each round. Compared to the old algorithm that would only move one shard in each round (every 10 seconds). The new algorithm is recommended and will become the default in future versions of Akka, but currently you have to enable it explicitly as described in the documentation.

Credits

For this release we had the help of 16 committers – thank you all very much!

commits  added  removed
     23   3156      823 Patrik Nordwall
      9     17       24 yiksanchan
      6    995      137 Johan Andrén
      5    382      142 Christopher Batey
      5    159       57 Renato Cavalcanti
      4    145       14 Muskan Gupta
      3    321        8 Ignasi Marimon-Clos
      3     10        3 Arnout Engelen
      1    688      308 r-glyde
      1     24        9 Adrian
      1      3        3 Seth Tisue
      1      1        2 Johannes Rudolph
      1      1        1 Evan Chan
      1      1        1 Josep Prat
      1      1        1 Upapan Vongkiatkachorn
      1      1        1 Stefano Baghino

Lightbend employs the Akka core team. If you’re looking to take your Akka systems to the next level, let’s set up a time to discuss our enterprise-grade expert support, self-paced education courses, and technology enhancements that help you manage, monitor and secure your Akka systems - from development to production.

Happy hakking!

– The Akka Team