Redlock is an algorithm for distributed locks on top of a cluster of uncoordinated Redis instances. redlock-clj is a redlock implementation in Clojure leveraging on the Carmine Redis client.
Algorithm and reference implementation by Salvatore Sanfilippo.
Leiningen: add the following to the :dependencies vector in project.clj
[redlock-clj "0.1.0"]Require redlock-clj
(require '[redlock-clj.core :as redlock])Define a cluster as a vector of connection options (see Carmine for details, in particular the docs for wcar):
(def cluster [{:pool {<opts1>} :spec {<opts1>}}
{:pool {<opts2>} :spec {<opts2>}}
{:pool {<opts3>} :spec {<opts3>}}])e.g.
(def cluster [{:spec {:host "http://127.0.0.1" :port 6379}}
{:spec {:host "http://127.0.0.1" :port 6380}}
{:spec {:host "http://127.0.0.1" :port 6381}}])The API consists of two functions, used for locking and unlocking a resource:
(defn lock! [cluster resource ttl & {:keys [retry-count retry-delay clock-drift-factor]}])returning either a lock map {:validity <validity-time> :resource <resource> :value <value>}, where value is a random uuid created by the client acquiring the lock, or nil in case the lock can't be acquired;
(defn unlock! [cluster lock])which unlocks a previously acquired lock.
Look at the test for an example of a distributed lock around a file-based counter.
Run the test with lein test after starting at least two out of three redis-server instances with ports 6379, 6380, 6381.
Copyright © 2014 Luca Antiga
Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.