Awesome Open Source
Awesome Open Source


A simple, high-performance event-driven HTTP client+server for Clojure

CHANGELOG | API | current Break Version:

[http-kit "2.5.3"]  ; Published by contributors, see CHANGELOG for details
[http-kit "2.1.19"] ; Legacy, published by @shenfeng

Project status

http-kit's author (@shenfeng) unfortunately hasn't had much time to maintain http-kit recently. To help out I'll be doing basic issue triage, accepting minor/obvious PRs, etc.

A big thank you to the current contributors for keeping the project going! Additional contributors welcome: please ping me if you'd be interested in lending a hand.

See the (unmaintained, outdated) project website for original documentation, examples, benchmarks, etc.

- @ptaoussanis


  • Ring compliant: HTTP Kit is an (almost) drop-in replacement for the standard Ring Jetty adapter. So you can use it with all your current libraries (e.g. Compojure) and middleware.

  • High performance: Using an event-driven architecture like Nginx, HTTP-kit is very, very fast. It comfortably handles tens of thousands of requests/sec on even midrange hardware. Here is another test about how it stacks up with others.

  • High concurrency: It's not only fast, but efficient! Each connection costs nothing but a few kB of memory. RAM usage grows O(n) with connections.

  • Clean, simple, small: Written from the ground-up to be lean, the entire client/server is available as a single ~90kB JAR with zero dependencies and ~3k lines of (mostly Java) code.

  • Sync or async: Synchronous is simple. Asynchronous is fast & flexible. With HTTP Kit you get the best of both with a simple API that lets you mix & match to best fit your use case.

  • WebSockets and Comet: With great out-the-box support for both WebSockets and efficient handling of long-held HTTP requests, realtime web applications are a breeze to write.

Enabling client SNI support (DISABLED BY DEFAULT)

To retain backwards-compatibility with JVMs < 8, http-kit client's SNI support is DISABLED by default.

Common cause of: Received fatal alert: handshake_failure

This default may be changed in a future breaking release. In the meantime, manually enabling support is easy:

  (:require [org.httpkit.sni-client :as sni-client]) ; Needs Java >= 8, http-kit >= 2.4.0-alpha6

  ;; Change default client for your whole application:
  (alter-var-root #'org.httpkit.client/*default-client* (fn [_] sni-client/default-client))

  ;; or temporarily change default client for a particular thread context:
  (binding [org.httpkit.client/*default-client* sni-client/default-client]

See org.httpkit.client/*default-client* docstring for more details.

Hack locally

Hacker friendly: zero dependencies, written from the ground-up with only ~3.5k lines of code (including java), clean and tidy.

# Modify as you want, unit tests back you up:
lein test

# May be useful (more info), see `server_test.clj`:

# Some numbers on how fast can http-kit's client can run:
lein test :benchmark

Contact & Contribution

Please use the GitHub issues page for feature suggestions, bug reports, or general discussions. Current contributors are listed here. The project website is also on GitHub.

Native Image

http-kit server and client are compatible with GraalVM's native-image compiler.

To ensure the image can build, provide the following options to the native-image compiler:


In your reflection-config.json

{"name": "java.lang.reflect.AccessibleObject",
 "methods" : [{"name":"canAccess"}]}

Class initialization

As of version 2.5.2 add the following flags:



Copyright © 2012-2020 @shenfeng and contributors. Distributed under the Apache License Version 2.0.

Get A Weekly Email With Trending Projects For These Topics
No Spam. Unsubscribe easily at any time.
Java (705,803
Clojure (24,719
Websocket (5,268
Async (3,113
Http Server (1,440
Http Client (1,257
Related Projects