Bazel Blog

Bazel 0.4.0 Released

We are delighted to announce the 0.4.0 release of Bazel. This release marks major improvements in support for Windows, sandboxing and performance.

We are also moving also moving to a new domain. is already up and running and we are slowly moving every reference to point to that new domain..

Improvements from our roadmap

Java workers are now used by default

Java workers reduce the time of java compilation by keeping a hot JVM in the background. It improves java compilation speed by 5x and we decided to make it the default.

Sandboxing is now working also on OS X

With our Beta release, we added sandboxing of action to Linux. This feature ensured that the rule set does not access undeclared input, allowing correct execution of actions. We leveraged the sandbox-exec command to generate a similar sandbox on OS X.

Other major changes since 0.3.0

We provide Bazel binaries for Windows

As announced in our Bazel on Windows blog post, we are now providing binary distribution of Bazel for Windows. A chocolatey package was contributed by Peter Mounce so you can just do choco install bazel to get Bazel installed on Windows, big thanks to Peter Mounce! This release also marks a big step for us: TensorFlow PIP package can now be built on Windows with Bazel!

Skylark implementation of repository rules

We now have implementation of two repository rules (gitrepository and mavenjar) in Skylark and we recommend using them instead of the native ones, to do so simply adds the following lines at the top of your WORKSPACE file:

load("@bazel_tools//tools/build_defs/repo:maven_rules.bzl", "maven_jar")

And various more

  • The --watchfs flag is ready to be turned on by default. It improves performance of Bazel, try it out!
  • The Linux sandbox got revamped for better performance and usability: no performance hit should be perceptible and accessing system tools should be possible.

For changes since 0.3.2 (the minor version before 0.4.0), see the release notes for changes.

Future plans

Looking ahead to 0.5.0:

  • With the help of your feedback, we will resolve the last issue to make our Windows port work seamlessly for Java, C++ and Python.
  • The new distributed execution API will be stabilized.


A big thank you to our community for your continued support. Particular shout-outs to the following contributors:

Thank you all, keep the discussion and bug reports coming!