Adding details on how to easily test the Kafka integration

Author: hartfordfive

KAFKA_TESTING.md

@@ -0,0 +1,56 @@
+## How to test the Kafka integration
+
+1. Ensure you have docker setup on your system.
+
+2. Create the following config and save it as `docker-compose-kafka-single.yml`
+```
+---
+version: '2'
+
+services:
+  zookeeper:
+    image: confluentinc/cp-zookeeper:latest
+    hostname: zookeeper
+    ports:
+      - 32181:32181
+    environment:
+      ZOOKEEPER_CLIENT_PORT: 32181
+      ZOOKEEPER_TICK_TIME: 2000
+    extra_hosts:
+      - "moby:127.0.0.1"
+      - "localhost: 127.0.0.1"
+
+  kafka:
+    image: confluentinc/cp-kafka:latest
+    hostname: kafka
+    ports:
+      - 9092:9092
+    depends_on:
+      - zookeeper
+    environment:
+      KAFKA_BROKER_ID: 1
+      KAFKA_ZOOKEEPER_CONNECT: zookeeper:32181
+      KAFKA_ADVERTISED_LISTENERS: PLAINTEXT://localhost:9092
+      KAFKA_AUTO_CREATE_TOPICS_ENABLE: "true"
+      KAFKA_OFFSETS_TOPIC_REPLICATION_FACTOR: 1
+    extra_hosts:
+      - "moby:127.0.0.1"
+      - "localhost: 127.0.0.1"
+```
+
+3. Create the kafka cluster:
+```
+docker-compose -f docker-compose-kafka-single.yml up
+```
+
+4. Create the necessary topic:
+```
+docker-compose -f docker-compose-kafka-single.yml exec kafka kafka-topics --create --bootstrap-server localhost:9092 --replication-factor 1 --partitions 1 --topic grok_exporter_test
+```
+
+5. Publish a sample test message:
+```
+docker-compose -f docker-compose-kafka-single.yml exec bash -c "echo 'this is a test' | kafka-console-producer --request-required-acks 1 --broker-list localhost:9092 --topic grok_exporter_test"
+  ```
+
+6. Given that the grok_exporter was properly configured and you're matching for a string in the message you've previously published to kafka, you should have matches that appear on the metrics page.