Adds helper functions for working with transducers and two examples.

examples/simple-ledger/.gitignore

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+log/

examples/simple-ledger/README.md

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+# Simple Ledger
+
+This example creates a simple accounting ledger using transducers.

examples/simple-ledger/deps.edn

@@ -1,19 +1,28 @@
-{:deps
- {danlentz/clj-uuid {:mvn/version "0.1.7"}
-  fundingcircle/jackdaw {:mvn/version "0.6.4"}
-  org.apache.kafka/kafka-streams {:mvn/version "2.1.0"}
-  org.apache.kafka/kafka-streams-test-utils {:mvn/version "2.1.0"}
-  org.clojure/clojure {:mvn/version "1.10.0"}
-  org.clojure/tools.logging {:mvn/version "0.4.1"}}
+{:paths
+ ["src" "resources"]
 
- :mvn/repos
- {"confluent" {:url "https://packages.confluent.io/maven/"}}
-
- :paths
- ["src" "test" "dev" "../dev"]
+ :deps
+ {fundingcircle/jackdaw {:mvn/version "0.6.9-transducers-SNAPSHOT"
+                         :exclusions [org.apache.zookeeper/zookeeper]}
+  org.clojure/clojure {:mvn/version "1.10.1"}
+  org.clojure/tools.logging {:mvn/version "0.4.1"}
+  org.apache.kafka/kafka-streams {:mvn/version "2.3.0"}
+  org.apache.kafka/kafka-streams-test-utils {:mvn/version "2.3.0"}
+  ch.qos.logback/logback-classic {:mvn/version "1.2.3"}
+  integrant {:mvn/version "0.7.0"}}
 
  :aliases
- {:test {:extra-deps {com.cognitect/test-runner
-                      {:git/url "https://github.com/cognitect-labs/test-runner.git"
-                       :sha "028a6d41ac9ac5d5c405dfc38e4da6b4cc1255d5"}}
-         :main-opts ["-m" "cognitect.test-runner"]}}}
+ {:dev
+  {:extra-paths ["dev" "../../dev"]
+   :extra-deps {integrant/repl {:mvn/version "0.3.1"}
+                danlentz/clj-uuid {:mvn/version "0.1.7"
+                                   :exclusions [primitive-math]}}}
+
+  :test
+  {:extra-paths ["test"]
+   :extra-deps {com.cognitect/test-runner {:git/url "https://github.com/cognitect-labs/test-runner.git"
+                                           :sha "028a6d41ac9ac5d5c405dfc38e4da6b4cc1255d5"}}
+   :main-opts ["-m" "cognitect.test-runner"]}}
+
+ :mvn/repos
+ {"confluent" {:url "https://packages.confluent.io/maven/"}}}

examples/simple-ledger/dev/user.clj

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+(ns user
+  "Use this namespace for interactive development.
+
+  This namespace requires libs needed to reset the app and helpers
+  from `jackdaw.repl`. WARNING: Do no use `clj-refactor` (or
+  equivalent) to clean this namespace since these tools cannot tell
+  which libs are actually required."
+  (:gen-class)
+  (:require [clojure.string :as str]
+            [clojure.tools.logging :refer [info]]
+            [integrant.core :as ig]
+            [integrant.repl :refer [clear go halt prep init reset reset-all]]
+            [jackdaw.admin :as ja]
+            [jackdaw.serdes :as js]
+            [jackdaw.repl :refer :all]
+            [jackdaw.streams :as j]
+            [jackdaw.streams.xform :as jxf]
+            [simple-ledger :as sl]))
+
+
+(def repl-config
+  "The development config.
+  When the 'dev' alias is active, this config will be used."
+  {:topics {:client-config (select-keys sl/streams-config ["bootstrap.servers"])
+            :topic-metadata {:entry-added
+                             {:topic-name "entry-requested"
+                              :partition-count 15
+                              :replication-factor 1
+                              :key-serde (js/edn-serde)
+                              :value-serde (js/edn-serde)}
+
+                             :transaction-pending
+                             {:topic-name "transaction-pending"
+                              :partition-count 15
+                              :replication-factor 1
+                              :key-serde (js/edn-serde)
+                              :value-serde (js/edn-serde)}
+
+                             :transaction-added
+                             {:topic-name "transaction-added"
+                              :partition-count 15
+                              :replication-factor 1
+                              :key-serde (js/edn-serde)
+                              :value-serde (js/edn-serde)}}}
+
+   :topology {:topology-builder sl/topology-builder
+              :xforms [#'sl/xf-split-entries #'sl/xf-running-balances]
+              :swap-fn jxf/kv-store-swap-fn}
+
+   :app {:streams-config sl/streams-config
+         :topology (ig/ref :topology)
+         :topics (ig/ref :topics)}})
+
+
+(integrant.repl/set-prep! (constantly repl-config))
+
+
+(defmethod ig/init-key :topics [_ {:keys [client-config topic-metadata] :as opts}]
+  (with-open [client (ja/->AdminClient client-config)]
+    (ja/create-topics! client (vals topic-metadata)))
+  (assoc opts :topic-metadata topic-metadata))
+
+(defmethod ig/init-key :topology [_ {:keys [topology-builder xforms swap-fn]}]
+  (let [xform-map (reduce-kv (fn [m k v]
+                               (let [k (keyword (str (:ns (meta v)))
+                                                (str (:name (meta v))))]
+                                 (assoc m k #(v % jxf/kv-store-swap-fn))))
+                               {}
+                               xforms)
+        streams-builder (j/streams-builder)]
+    ((topology-builder topic-metadata xform-map) streams-builder)))
+
+(defmethod ig/init-key :app [_ {:keys [streams-config topology] :as opts}]
+  (let [streams-app (j/kafka-streams topology streams-config)]
+    (j/start streams-app)
+    (assoc opts :streams-app streams-app)))
+
+(defmethod ig/halt-key! :topics [_ {:keys [client-config topic-metadata]}]
+  (let [re (re-pattern (str "(" (->> topic-metadata
+                                     keys
+                                     (map name)
+                                     (str/join "|"))
+                            ")"))]
+    (re-delete-topics client-config re)))
+
+(defmethod ig/halt-key! :app [_ {:keys [streams-config topics streams-app]}]
+  (j/close streams-app)
+  (destroy-state-stores streams-config)
+  (let [re (re-pattern (str "(" (get streams-config "application.id") ")"))]
+    (re-delete-topics (:client-config topics) re)))

examples/simple-ledger/resources/logback.xml

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+../../resources/logback.xml