Gearman vs Kestrel: What are the differences?

Developers describe Gearman as "A generic application framework to farm out work to other machines or processes". Gearman allows you to do work in parallel, to load balance processing, and to call functions between languages. It can be used in a variety of applications, from high-availability web sites to the transport of database replication events. On the other hand, Kestrel is detailed as "Simple, distributed message queue system". Kestrel is based on Blaine Cook's "starling" simple, distributed message queue, with added features and bulletproofing, as well as the scalability offered by actors and the JVM.

Gearman and Kestrel can be primarily classified as "Message Queue" tools.

Some of the features offered by Gearman are:

• Open Source It’s free! (in both meanings of the word) Gearman has an active open source community that is easy to get involved with if you need help or want to contribute. Worried about licensing? Gearman is BSD
• Multi-language - There are interfaces for a number of languages, and this list is growing. You also have the option to write heterogeneous applications with clients submitting work in one language and workers performing that work in another
• Flexible - You are not tied to any specific design pattern. You can quickly put together distributed applications using any model you choose, one of those options being Map/Reduce

On the other hand, Kestrel provides the following key features:

• Written by Robey Pointer
• Starling clone written in Scala (a port of Starling from Ruby to Scala)
• Queues are stored in memory, but logged on disk

Kestrel is an open source tool with 2.8K GitHub stars and 326 GitHub forks. Here's a link to Kestrel's open source repository on GitHub.