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fr33m0nk/clj-bucket4j-datomic

Distributed Bucket4J implementation for Datomic Database <br/> Note: this library uses Clojure wrapper for Bucket4J, clj-bucket4j

How to find this library?

Add the following to your project dependencies:

CLI/deps.edn dependency information

net.clojars.fr33m0nk/clj-bucket4j-datomic {:mvn/version "0.1.2"}

Leningen/Boot

[net.clojars.fr33m0nk/clj-bucket4j-datomic "0.1.2"]

Maven

<dependency>
  <groupId>net.clojars.fr33m0nk</groupId>
  <artifactId>clj-bucket4j-datomic</artifactId>
  <version>0.1.2</version>
</dependency>

Gradle

implementation("net.clojars.fr33m0nk:clj-bucket4j-datomic:0.1.2")

Usage

Add Datomic peer dependency in you project if not present.

Prior to using below functions, it is necessary to execute these Datomic migrations

All functions are available through the `fr33m0nk.clj-bucket4j-datomic` namespace

Important Functions:

Name	Description
`fr33m0nk.clj-bucket4j-datomic/->datomic-proxy-manager`	Returns Distributed Bucket4J Proxy Manager for Datomic
`fr33m0nk.clj-bucket4j-datomic/add-distributed-bucket`	Adds a distributed bucket to Datomic. NOOP if bucket already exists.<br/> Returns the instance of bucket
`fr33m0nk.clj-bucket4j-datomic/remove-distributed-bucket`	Removes a distributed bucket. <br/> Permanent removal is determined by the RecoveryStrategy chosen while creating the bucket.<br/> Default strategy is to always RestoreOnDelete

Example:

as a distributed throttler

Suppose you need to have a fresh exchange rate between dollars and euros. To get the rate you continuously poll the third-party provider, and by contract with the provider you should poll not often than 100 times per 1 minute, else provider will block your IP:

(require '[datomic.api :as d] '[fr33m0nk.clj-bucket4j :as b4j] '[fr33m0nk.datomic-schema :refer [b4j-schema]] '[fr33m0nk.clj-bucket4j-datomic :as b4j-datomic])
(import '(io.github.bucket4j.distributed.proxy ClientSideConfig))

(def datomic-conn (return-datomic-connection))

;; Execute Datomic migrations for supporting Distributed Bucket4J
@(d/transact datomic-conn b4j-schema)

;; Instance of datomic-proxy-manager
;; For most cases `(ClientSideConfig/getDefault)` is enough
;; Look into documentation of ClientSideConfig to figure right scenarios to customize it
(def datomic-proxy-manager (b4j-datomic/->datomic-proxy-manager datomic-conn (ClientSideConfig/getDefault)))

;; Bucket configuration allowing 100 hits in 60000 ms (1 minute)
(def bucket-configuration (-> (b4j/bucket-configuration-builder)
                              (b4j/add-limit (b4j/simple-bandwidth 100 60000))
                              (b4j/build)))

;; Adds a distributed bucket to Datomic
(def distributed-bucket (b4j-datomic/add-distributed-bucket datomic-proxy-manager "test-bucket-1" bucket-configuration))

(def exchange-rates (atom 0.0))

;; do polling in infinite loop
(while true
  ;; Consume a token from the token bucket.
  ;; Depending on the availability of Token, `b4j/try-consume` returns true or false.
  (when (b4j/try-consume distributed-bucket 1)
    (swap! exchange-rate #(identity %2) (poll-exchange-rate))))

More detailed usages of above functions and more can be found in tests.

License

Distributed under the MIT License.