Quasar is an open source JVM library that greatly simplifies the creation of highly concurrent software that is very easy to write and reason about, performant, and fault tolerant.
Quasar’s core implements true lightweight threads on the JVM called fibers. Fibers can be instantiated and run just like regular threads, but rather than a few thousand of threads, a single JVM can easily run hundreds of thousands or even millions of fibers.
Fibers enjoy the scalability and performance benefits of asynchronous (callback-based) programming while still maintaining the simplicity, intuitiveness and familiarity of threaded code. No need for confusing callbacks or functional constructs.
Fibers use channels (CSP), data-flow variables, or other forms of coordination, to communicate with one another efficiently.
On top of fibers, Quasar provides an actor framework that strongly resembles Erlang’s. Actors are a simple and natural way to implement a scalable and fault-tolerant business logic.