6.5. Agents

Clojure provides a special construct called an agent that allows for asynchronous and independent changes to shared mutable data. The agent function allows the creation of agents, which hold values that can be changed using special functions. Clojure provides two functions, send and send-off, that result in mutating the value of an agent. Both accept the agent that needs to be updated, along with a function that will be used to compute the new value. The application of the function happens at a later time, on a separate thread. By corollary, an agent is also useful to run a task (function) on a different thread, with the return value of the function becoming the new value of the agent. The functions sent to agents are called actions.

Creating an agent is similar to creating a ref: