This is brand new. There are surely bugs, and things will break and change.
Drawbridge is available in Clojars. Add this
:dependency to your Leiningen
Or, add this to your Maven project's
<repository> <id>clojars</id> <url>http://clojars.org/repo</url> </repository> <dependency> <groupId>com.cemerick</groupId> <artifactId>drawbridge</artifactId> <version>0.0.6</version> </dependency>
Drawbridge is compatible with Clojure 1.2.0 - 1.4.0.
While nREPL provides a solid REPL backend for Clojure, typical socket-based channels are often unsuitable. Being able to deploy applications that allow for REPL access via HTTP and HTTPS simplifies configuration and can alleviate security concerns, and works around limitations in various deployment environments where traditional socket-based channels are limited or entirely unavailable.
In a Ring web application
Once you have added Drawbridge to your project's dependencies, just add its Ring handler to your application. For example, if you're using Compojure for routing and such:
(require 'cemerick.drawbridge) (let [nrepl-handler (cemerick.drawbridge/ring-handler)] (ANY "/repl" request (nrepl-handler request)))
With this, any HTTP or HTTPS client can send nREPL messages to the
/repl URI, and read responses from the same. Conveniently, any
security measures applied within your application will work fine in
conjunction with Drawbridge; so, if you configure its route to require
authentication or authorization to some application-specific role, those
prerequisites will apply just as with any other Ring handler in the same
Some things to be aware of when using
- It requires
POSTrequests to be routed to whatever URI to which it is mapped; other request methods result in an HTTP error response.
- It requires these standard Ring middlewares to function properly:
Especially if you are going to be connecting to your webapp's nREPL endpoint with a client that uses Drawbridge's own HTTP/HTTPS client transport (see below), this is all you need to know.
If you are interested in the implementation details and semantics,
perhaps because you'd like to implement support for Drawbridge in
non-Clojure nREPL clients, you'll want to review the documentation for
ring-handler, which contains additional important details.
In Clojure tooling
Drawbridge also provides a client-side nREPL transport implementation
for the Ring handler in
Note that the
cemerick.drawbridge.client namespace implicitly adds
implementations to the
clojure.tools.nrepl/url-connect multimethod for
"https" schemes. So, once this namespace is loaded, any
tool that uses
url-connect will use
connecting to HTTP and HTTPS nREPL endpoints.
The biggest outstanding issues are around the semantics of how HTTP session (might optionally) map onto nREPL sessions. Right now, they don't at all, though HTTP sessions are significant insofar as they retain the message queue nREPL will dispatch responses to that are emitted by asynchronous or long-running operations.
Secondarily, supporting nontextual REPL interactions over HTTP has not yet been addressed at all.
Copyright © 2012 Chas Emerick and other contributors.
Distributed under the Eclipse Public License, the same as Clojure.