Open Source at Improbable – FlagZ and Polyglot

Last week we spoke about some of the amazing projects that help us build better software faster and more safely. This week, we are announcing the open source release of two projects, developed in house and used extensively on a daily basis: FlagZ and Polyglot.


FlagZ is an annotations-based flag library for Java, Scala and Go. FlagZ allow developers to specify variables inside their code to be externally modifiable, either through command line interface parameters at start up, or dynamically during the program’s execution. FlagZ, when used in conjunction with etcd, allows users to change any given variable on all servers simultaneously. FlagZ can be found here for Java and Scala, and here for Go.


Polyglot is a universal gRPC client. gRPC is Google’s open sourced RPC protocol, and is our weapon of choice for communication between services within our platform. Polyglot addresses the need for many small client binaries in order to test and iterate. You can find out more about Polyglot on GitHub.

Improbable at CoreOS Fest

We hope these tools provide value to some users, and welcome contributions! Don’t miss a chance to chat to FlagZ creator, Michał Witkowski, in Berlin at CoreOS Fest.

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