altman

Kafka Streams framework for Clojure and (soon) Event Sourcing.

Hotlips O'Houlihan: I wonder how a degenerated person like that could have reached a position of responsibility in the Army Medical Corps!
Father Mulcahy: He was drafted.

Lola Johnson: What if you die some day?
Garrison Keillor: I will die.
Lola Johnson: Don't you want people to remember you?
Garrison Keillor: I don't want them to be told to remember me.

Views

The org.purefn.altman.views namespace provides an RPC layer for Kafka Streams Interactive Queries.

The component constructed by the server function in this namespace will start an Immutant web server (on port 8000 by default) which accepts edn web requests at the /state endpoint. This component should receive queryable streams apps as dependencies in this system map like so:

(require '[ladders-domains.recruiter.save-candidates :as candidate])

(component/system-map
   :views
   (component/using (views/server)
                    [:projects-view-app
                     :project-candidates-view-app]) 
   :projects-view-app
   (->> (processor/simple-processor event-processor/projects-processor
                                    :inputs ["recruiter.save.candidates.events"])
        (streams/streams-app (:projects-view config))
        (views/queryable ::candidate/project-view))
   :project-candidates-view-app
   (->> (processor/simple-processor event-processor/project-candidates-processor
                                    :inputs ["recruiter.save.candidates.events"])
        (streams/streams-app (:project-candidates-view config))
        (views/queryable ::candidate/project-candidates-view))

Any number of streams apps are supported. The namespaced keyword passed to the views/queryable function should correlate with a usage of defview, e.g.

(ns ladders-domains.recruiter.save-candidates
  (:require [org.purefn.irulan.view :as view])))

(view/defview ::project-view "ryan.platform")

This keyword is used in service discovery in the gatekeeper (Rashomon) and to access the correct streams app locally.

Once started the web server can be queried like

(require '[ladders-domains.recruiter.save-candidates :as candidate])
(require '[clj-http.client :as http])

(defn fetch-key
  [view-name k]
  (http/post "http://localhost:8000/state"
             {:form-params {:key k
                            :view-name view-name}
              :content-type :edn}))

(fetch-key ::candidate/project-view
           #uuid "00000002-0012-8002-c000-000000000000")

This is the same mechanism Rashomon uses to retrieve state for individual processors.

License

Copyright © 2017 Ladders

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.