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A clojure library for all things async.
Java Clojure
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This is still a very young project. As such, do not expect stability or documentation yet.

What is Momentum?

Momentum is a high performance asynchronous networking framework built for the Clojure programming language. Momentum is still very young and currently only supports HTTP, however there are plans to make it more generic for arbitrary network programming.

Currently, Momentum provides:

  • Generic async abstractions
  • A general networking abstraction
  • Middleware for HTTP (client and server)
  • A connection pool for client HTTP connections.

Yes, the README is still quite lacking, but more will come. I just wanted to get this out to the world.


First, require the momentum namespace. Then:

    (fn [downstream env]
      (fn [evt val]
        (when (= :request evt)
          (downstream :response [200 {"content-length" "5"} "Hello"])))))

More details will come, but for now, there are fairly extensive tests.


  • More documentation
  • A lot more goodness

Why the Java?

Well, this was my first Clojure project. I'm still getting used to the idioms. Also, my use cases for this was fairly performance sensitive, and some things, I couldn't quite figure out how to do efficiently in Clojure.

Why not Aleph?

I definitely checked out Aleph & Lamina before writing Momentum. I think that Aleph is really a great project and I learned a lot reading the source to it. I wrote Momentum for a few reasons. First of all, Aleph was a lot less mature when I first started; it has evolved and grown a lot since. Second, Aleph / Lamina has no mechanism to handle slow consumers. While this might sound as a minor concern, this has fairly wide spread repercussions. Third, I wanted a base abstraction that was as light as possible. Aleph's base abstraction is a channel, which is fairly heavy weight. Momentum's base abstraction is a function and closures.

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