Akka Projections - Ditch the Message Broker, Go Faster - Read Blog

Scala sbt 1.1.4 patch notes

Eugene Yokota Scala Team, Lightbend, Inc.

Hi everyone. sbt 1.1.4 hotfix is released!

Bug fixes


Triggered execution on macOS

sbt has long had issues with triggered execution on macOS. Ethan Atkins has contributed a fix for this problem by merging MacOSXWatchService from his CloseWatch. Thanks, Ethan!

Credit also goes to Greg Methvin and Takari’s directory-watcher. #3860/#4071/io#138 by @eatkins

Running sbt with standby

One of the tricky things you come across while profiling is figuring out the process ID, while wanting to profile the beginning of the application.

For this purpose, we’ve added sbt.launcher.standby JVM flag. Starting sbt 1.1.4, you can run:

$ sbt -J-Dsbt.launcher.standby=20s exit

This will count down for 20s before doing anything else. launcher#51 by @eed3si9n

Loading performance improvement

Using Flame graph (if you haven’t yet, check out Profiling JVM applications post), Jason Zaugg identified hashing code of the build file to be one of the hot paths during sbt startup. Flame graph supports Ctrl+F to filter on method names; and when I ran it, it showed 4.5% of the time was spent in Eval#evalCommon method.


Instead of creating an intermediate Array[Byte] and passing it to MessageDigest at the end, Jason suggested that we pass the arrays to MessageDigest#update in a more procedural style. After confirming that it worked, we’ve next identified file timestamp code to be the next bottle neck using Flame graph, so that was switched to using NIO. After both changes, Eval#evalCommon’s footprint reduced to 2.3%.

This means that your build loads slightly faster on sbt 1.1.4 (about 0.54s faster on akka/akka, for example). #4067 by @eed3si9n


A huge thank you to everyone who’s helped improve sbt and Zinc 1 by using them, reporting bugs, improving our documentation, porting builds, porting plugins, and submitting and reviewing pull requests.

sbt 1.1.4 was brought to you by 11 contributors, according to git shortlog -sn --no-merges v1.1.2...v1.1.4 on sbt, zinc, librarymanagement, util, io, launcher-package, and website: Eugene Yokota, Dale Wijnand, 杨博 (Yang Bo), Ethan Atkins, Sam Halliday, Aaron S. Hawley, Gabriele Petronella, Jason Steenstra-Pickens, Jason Zaugg, Julien Jean Paul Sirocchi, and aumann.

For anyone interested in helping sbt, there are many avenues you could help, depending on your interest.

  • Migrate library builds to sbt 1, or update plugins.
  • Report bugs when you see them.
  • Send in fixes to bugs.
  • Update documentation.

If you’re interested in other ideas, come talk to us on sbt-contrib or on the brand new Lightbend Discuss.


The Total Economic Impact™
Of Lightbend Akka

  • 139% ROI
  • 50% to 75% faster time-to-market
  • 20x increase in developer throughput
  • <6 months Akka pays for itself