Intemporal demo with in-memory store

Requirements

(ns intemporal.doc
  (:require
    [intemporal.store :as s]
    [intemporal.workflow :as w]
    [intemporal.activity :as a]
    [automata.fsm :as fsm]))

Implementing an FSM

(def resource-rules
  {:state/init     [{::fsm/event :event/create ::fsm/to :state/creating ::fsm/actions [:action/create]}
                    {::fsm/event :event/kill ::fsm/to :state/killed}]
   :state/creating [{::fsm/event :event/created ::fsm/to :state/down}
                    {::fsm/event :event/error ::fsm/to :state/init}]
   :state/down     [{::fsm/event :event/start ::fsm/to :state/starting ::fsm/actions [:action/start]}
                    {::fsm/event :event/kill ::fsm/to :state/killing ::fsm/actions [:action/kill]}]
   :state/starting [{::fsm/event :event/started ::fsm/to :state/up}
                    {::fsm/event :event/error ::fsm/to :state/down}]
   :state/stopping [{::fsm/event :event/stopped ::fsm/to :state/down}
                    {::fsm/event :event/error ::fsm/to :state/up}]
   :state/up       [{::fsm/event :event/stop ::fsm/to :state/stopping ::fsm/actions [:action/stop]}
                    {::fsm/event :event/kill ::fsm/to :state/killing ::fsm/actions [:action/kill]}]
   :state/killing  [{::fsm/event :event/killed ::fsm/to :state/killed}
                    {::fsm/event :event/error ::fsm/to :state/killing}]
   :state/killed   []})

Implementation

;; event producer
(defprotocol EventHandler
  (process-event [this event] "Processes the event, returns the next event"))

(defn make-event-handler []
  (reify EventHandler
    (process-event [this event]
      (let [nxt (condp = event
                  :event/create :event/created
                  :event/created :event/start
                  :event/start :event/started
                  :event/started :event/stop
                  :event/stop :event/stopped
                  :event/stopped :event/kill
                  :event/kill :event/killed
                  nil)]
        nxt))))

Workflow definition

(defn run-fsm-workflow
  [rules init-state init-event]
  (let [stub      (a/stub-protocol EventHandler (make-event-handler) {:idempotent true})
        initstate {::fsm/rules rules ::fsm/state init-state}]

    (loop [state initstate
           evt   init-event]
      (if-let [nxt (process-event stub evt)]
        (recur (fsm/transit state evt) nxt)
        state))))

Execution

(try
  (run-fsm-workflow resource-rules :state/init :event/create)
  (catch  js/Object err
    (js/console.error "Workflow failed!" err)))

Live example

Results

;;Results go here

In-browser results

Tasks

Events