Update README.md

Author: billonline33

README.md

@@ -1,2 +1,92 @@
 # kafka-nodejs-tutorial
-A sample application using Kafka, Node.js and Docker
+# A sample application using Kafka, Node.js and Docker
+
+## 1. About Kafka Streaming
+
+Below is the discription from the official Kafka web site.
+
+Apache Kafka® is a distributed streaming platform.
+
+It publishes and subscribes to streams of records, similar to a message queue or enterprise messaging syste
+
+Kafka is generally used for two broad classes of applications:
+
+Building real-time streaming data pipelines that reliably get data between systems or applications
+Building real-time streaming applications that transform or react to the streams of data
+
+To learn more about Kafka, please visit [Kafka official web site](https://kafka.apache.org/)
+
+Kafka is build in Java, it does provide APIs from many other lanhuages.
+
+Since I am a Javascript developer, I decided to use Node.js for this sample application.
+
+There are a few libraries for Node.js, some popular libraries include:
+
+* [node-rdkafka](https://github.com/Blizzard/node-rdkafka)
+
+* [Kafka-node](https://www.npmjs.com/package/kafka-node)
+
+* [KafkaJS](https://www.npmjs.com/package/kafkajs) 
+
+I use KafkaJs in this example. The main reason is it has better documentation then the other two.
+
+
+
+## 2. Use case - track travellers who may infected by Coronarirus virus
+
+We are going to build an applicaiton, to track petential travellers who may have been infected by Coronavirus.
+
+1. We check travellers temperature at major airports.
+2. Temperature and traveller's personal infomration are sent to the Kafka queue (as producer). Note every airport is a prodcuer.
+3. We have another app check every message sent to the queue (near real time), and alert is triggered if we a passenger has higher temperature and has overseas travel history.
+
+
+
+## 3. Build local Kafka environemnt using Docker and Container
+
+In order to run the application locally, we need at least two docker imagers
+
+* zookeeper
+* Kafka Broker
+
+In the real envirnment, you will need multiple Kafka brokers, to form a cluster.
+
+In stead of build my own docker imagers, I cloned the code from https://github.com/wurstmeister/kafka-docker, which give me everything I need to run Kafka on my local container
+
+
+
+
+
+```yml
+version: "2"
+services:
+  zookeeper:
+    image: wurstmeister/zookeeper
+    ports:
+      - "2181:2181"
+  kafka:
+    build: .
+    ports:
+      - "9092:9092"
+    environment:
+      KAFKA_ADVERTISED_HOST_NAME: localhost
+      KAFKA_ZOOKEEPER_CONNECT: zookeeper:2181
+      KAFKA_CREATE_TOPICS: "flight:1:1"
+    volumes:
+      - /var/run/docker.sock:/var/run/docker.sock
+
+```
+
+
+
+
+
+Reference: https://github.com/wurstmeister/kafka-docker
+
+
+## 4. Run the application
+
+
+
+## References
+