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https://github.com/ccann/gregor
Lightweight Clojure bindings for Apache Kafka
https://github.com/ccann/gregor
clojure java kafka queue
Last synced: about 2 months ago
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Lightweight Clojure bindings for Apache Kafka
- Host: GitHub
- URL: https://github.com/ccann/gregor
- Owner: ccann
- License: epl-1.0
- Archived: true
- Fork: true (vrih/gregor)
- Created: 2017-02-01T04:05:51.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2021-01-25T15:56:40.000Z (over 3 years ago)
- Last Synced: 2024-07-26T08:09:09.913Z (2 months ago)
- Topics: clojure, java, kafka, queue
- Language: Clojure
- Homepage:
- Size: 162 KB
- Stars: 23
- Watchers: 4
- Forks: 5
- Open Issues: 2
-
Metadata Files:
- Readme: README.md
- Changelog: CHANGELOG.md
- License: LICENSE
Awesome Lists containing this project
- awesome-kafka-in-clojure - ccann/gregor
README
# Gregor
Lightweight Clojure wrapper for [Apache Kafka](http://kafka.apache.org/) Consumer + Producer APIs.
```clojure
:dependencies [[org.clojure/clojure "1.10.0"]
[org.apache.kafka/kafka_2.12 "2.1.1"]]
```
[](https://cljdoc.org/d/io.weft/gregor/CURRENT)
[](https://clojars.org/io.weft/gregor)
[**CHANGELOG**](https://github.com/ccann/gregor/blob/master/CHANGELOG.md)
Gregor wraps most of the Java API for the Kafka [Producer](http://kafka.apache.org/0100/javadoc/index.html?org/apache/kafka/clients/producer/KafkaProducer.html) and [New Consumer](http://kafka.apache.org/0100/javadoc/index.html?org/apache/kafka/clients/consumer/KafkaConsumer.html) The goal of this project is to stay very close to the Kafka API instead of adding more advanced features.
## Example
Here's an example of at-least-once processing (using [`mount`](https://github.com/tolitius/mount)):
```clojure
(ns gregor-sample-app.core
(:gen-class)
(:require [clojure.repl :as repl]
[gregor.core :as gregor]
[mount.core :as mount :refer [defstate]]))
(def run (atom true))
(defstate consumer
:start (gregor/consumer "localhost:9092"
"testgroup"
["test-topic"]
{"auto.offset.reset" "earliest"
"enable.auto.commit" "false"})
:stop (gregor/close consumer))
(defstate producer
:start (gregor/producer "localhost:9092")
:stop (gregor/close producer))
(defn -main
[& args]
(mount/start)
(repl/set-break-handler! (fn [sig] (reset! run false)))
(while @run
(let [consumer-records (gregor/poll consumer)
values (process-records consumer-records)]
(doseq [v values]
(gregor/send producer "other-topic" v))
(gregor/commit-offsets! consumer)))
(mount/stop))
```
Transformations over consumer records are applied in `process-records`. Each record in
the `seq` returned by `poll` is a map. Here's an example with a JSON object as the
`:value`:
```clojure
{:value "{\"foo\":42}"
:key nil
:partition 0
:topic "test-topic"
:offset 939}
```
## Producing
Gregor provides the `send` function for asynchronously sending a record to a topic. There
are multiple arities which correspond to those of the `ProducerRecord`
[Java constructor](https://kafka.apache.org/0100/javadoc/org/apache/kafka/clients/producer/ProducerRecord.html). If
you'd like to provide a callback to be invoked when the send has been acknowledged use
`send-then` instead.
## Topic Management
Create a topic:
```clojure
(create-topic {:connection-string "localhost:2181"} "some-topic" {})
```
That empty map can be used to specify configuration for number of topic partitions, replication factor,
Delete a topic:
``` clojure
(delete-topic {:connection-string "localhost:2181"} "some-topic")
```
Query about a topic's existence:
``` clojure
(topic-exists? {:connection-string "localhost:2181"} "some-topic")
```
List existing topics:
``` clojure
(topics {:connection-string "localhost:2181"})
```
## License
Distributed under the Eclipse Public License either version 1.0 or (at your option) any
later version.