What is this

This is a toy project which implements a counter following this tutorial. Deployed it on a Kubernetes cluster.

Using Kotlin and Spring Boot 2.0 as backend
- There is a Redis instance storing the counter state
Using Vue as frontend

How to start

There are two ways to get start

Run the standalone container. You can check the available tag names here
Run from the source code

Run the standalone container

Docker is necessary to run this. docker run --rm -p 8888:8080 xzjia/kuboolin:${TAG_NAME}

Run from the source code

Server side

To spin up the server side, do the following.

# First have a redis instance running on localhost:6379

./gradlew bootRun

# Or build it into a jar and boot from there
./gradlew clean build
java -jar java -jar build/libs/kuboolin-0.0.1-SNAPSHOT.jar

Then, you can see the results on localhost:8080. I'm using HTTPie here as a replacement of curl.

$ http :8080/api/counter
HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8
transfer-encoding: chunked

{
    "asOf": "2018-05-31T16:32:51.384",
    "by": "JiaXiaozhous-MacBook-Pro.local",
    "value": 630
}


$ http PUT :8080/api/counter/up
HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8
transfer-encoding: chunked

{
    "asOf": "2018-05-31T16:32:57.932",
    "by": "JiaXiaozhous-MacBook-Pro.local",
    "value": 631
}


$ http PUT :8080/api/counter/down
HTTP/1.1 200 OK
Content-Type: application/json;charset=UTF-8
transfer-encoding: chunked

{
    "asOf": "2018-05-31T16:33:01.801",
    "by": "JiaXiaozhous-MacBook-Pro.local",
    "value": 630
}


$ http --stream :8080/api/counter Accept:text/event-stream
HTTP/1.1 200 OK
Content-Type: text/event-stream;charset=UTF-8
transfer-encoding: chunked

data:{
data:  "value" : 630,
data:  "type" : "UP",
data:  "at" : "2018-05-31T16:32:38.058",
data:  "by" : "JiaXiaozhous-MacBook-Pro.local"
data:}

data:{
data:  "value" : 631,
data:  "type" : "UP",
data:  "at" : "2018-05-31T16:32:57.933",
data:  "by" : "JiaXiaozhous-MacBook-Pro.local"
data:}

data:{
data:  "value" : 630,
data:  "type" : "DOWN",
data:  "at" : "2018-05-31T16:33:01.802",
data:  "by" : "JiaXiaozhous-MacBook-Pro.local"
data:}

Client side

To run a develop server, first navigate into kuboolin-board and then run yarn install & yarn dev. To make a production build, run yarn build. NOTE: the production built files are located at ./src/main/resources/public

Deployment

# First build the front end, inside kuboolin-board
yarn build

# Build the jar file
./gradlew clean build

# Build and push the docker image
docker build -t xzjia/kuboolin:${TAG_NAME} .
docker push xzjia/kuboolin:${TAG_NAME}

# Change the image in Kubernetes deployment
kubectl set image deployment/kuboolin kuboolin=xzjia/kuboolin:${TAG_NAME}

# To scale up and down, simple do
kubectl scale deployment kuboolin --replicas=${HOW_MANY_PODS}

Future work

No health check from the load balancer
- Figure out how to do this with Kubernetes
Redis endpoint, back end endpoint are hard coded in code
- Figure out how to setup EventSource without an absolute URL
When there are more than one pods, updates on one pod will not be sent to other pods
- Use something like Kafka to replace event bus
Due to some cache issues on browser, there will be situations that
Make it work with HTTPS, so that all static files can be served from an object storage

xzjia / kuboolin