Clockwork in a browser extension for Chrome and Firefox devtools, providing tools for debugging and profiling your application. This library is a Clojure backend counterpart for the extension.

There are two parts to clockwork: one is a Ring middleware and another is a couple of macros.

It's initialialized by wrapping your app in clockwork.core/wrap:

(def app (clockwork.core/wrap my-handler 
           {:authorized? (fn [req] (user/admin? req))}))

There are a couple of options for the middleware:

• :authorized? - this checks if a current user can access profiling information (by default all requests to localhost are allowed)
• :profile-request? - this checks if a request should be profiled: skipping static and media data seems logical (by default all authorized requests are profiled, except for requests for clockwork data)
• :prefix - prefix for all internal Clockwork requests (by default it's /__clockwork/)
• :store - store for Clockwork data (by default in-memory, for details see lower)

There are two types of timing information: trace and timing.

trace is a section of your code, where something happens: like request parsing, or maybe template rendering, etc - it shows up on nested timeline.

Signature: (trace section-name & body)

Example:

(clockwork/trace (str "app " (:uri req))
  (my-handler req))

timing is a call to some (external) resource, like database, cache lookup or internal http request. It shows in a DB tab.

Signature: (timing type description & body)

Example:

(defn q [query]
  (clockwork/timing "pg" (pr-str query) 
      (jdbc/query db-conn (query->args query))))
      
(defn cache-get [key]
  (clockwork/timing "cache get" key (.get memcache key)))

Default store is an in-memory one, just holding everything in an atom. Of course, this works well enough only if you have a single application process - and if you have multiple, you have to provide your own. Here is an example of using memcached as a store:

(defrecord CWStore [mc prefix]
  clockwork.store/Storage
  (save [this id data]
    (try (.set mc (str prefix id) 100000 data)
         (catch Exception e nil)))
  (fetch [this id]
    (try (.get mc (str prefix id))
         (catch Exception e nil))))