Cloud Native Kotlin

Kotlin-based version of Josh Long's 'Cloud Native Java' code

Pre-requisites

• RabbitMQ installed and running.

Running

Reservation Application Microservice ecosystem

# (1) Start Cloud Config server (wait until started)
# Port: 8888
./gradlew :cloud-config:bootRun

# (2) Start Eureka Server
# Port: 8761
./gradlew :eureka-service:bootRun

# (3) Start Auth Service (OAuth2)
# Port: 9191
./gradlew :auth-service:bootRun

# (3) Start Hystrix Dashboard 
# Port: 8889
./gradlew :hystrix-dashboard:bootRun

# (4) Start Zipkin Service (Distributed message tracing)
# Port: 9411
./gradlew :zipkin-service:bootRun

# (5) Start Reservation service (microservice)
# Port: 8080
./gradlew :reservation-service:bootRun

# (6) Start Reservation client (Zuul proxy, API Gateway, Circuit Breaker) 
# Port: 8081
./gradlew :reservation-client:bootRun

# (7) Start DataFlow server (optional)
# Port: 9393
./gradlew :dataflow-service:bootRun

Spring Cloud Config

The configuration properties are served from a Spring Cloud Config Server, running on port 8888

Some beans that have @RefreshScope annotation can have properties refreshed without restarting. If a property value changed on the config server, to trigger a refresh, execute POST /admin/refresh on the microservice itself.

Spring Boot Actuator

Base Url for actuator endpoints are located at /admin/

Git commit info of running instance

Git commit information can be found at /admin/info

API Gateway

Viewing

To view list of reservation names via API Gateway (that relays to the reservation service via reservation client):

GET /reservations/names
HEADER:
- Authorization: Bearer [bearer-token]

This endpoint has a Circuit Breaker (Hystrix) which falls back to a method that provides an empty list in case of failure of execution of original method.

Creating

To add to the list of reservations, we can POST to our gateway and send the payload over the wire as a message, via Spring Cloud Stream with RabbitMQ as the backing message queue.

The reservation client has a property for binding output in reservation-client.yml in cloud config and has a Source binding in declaration.

spring.cloud.stream.bindings.output.destination: reservations

The reservation service has a property for binding input in reservation-service.yml in cloud config and has a Sink binding in declaration.

spring.cloud.stream.bindings.input.destination: reservations

The endpoint on the Reservation client side is:

POST /reservations
HEADER:
- Content-Type: application/json
- Authorization: Bearer [bearer-token]

{ "reservationName" : "content" }

Zuul Proxy

reservation-client is a Zuul proxy, which relays service requests to a configured REST API.

To access reservation-service REST API endpoints, reservation-client has endpoints such as:

GET /reservation-service/reservations

Which calls Reservation service itself, acting as a proxy.

Hystrix Dashboard

Navigate to http://localhost:8889/hystrix to find the Hystrix dashboard.

To view Hystrix metrics for reservation-client, enter http://localhost:8081/hystrix.stream into the main panel

Authentication Service (OAuth2)

An in-memory implementation of password grant type.

To get an OAuth token, call the Auth service:

POST localhost:9191/oauth/token
Headers:
- Content-Type: application/x-www-form-urlencoded
- Accept: application/json
- Authorization: Basic [base64(html5/password)]
Body
- password: test123
- username: jdoe
- grant_type: password
- scope: openid
- client_secret: password
- client_id: html5

e.g. body:
password=test123&username=jdoe&grant_type=password&scope=openid&client_secret=password&client_id=html5

Reservation client is protected by OAuth2, so to be able to access any resources, each request will need an Authorization Bearer header (with a bearer token retrieved from Auth service):

GET localhost:8081/reservations/names
HEADER:
- Authorization: Bearer [bearer-token]

Spring Cloud DataFlow

dataflow-service is a Spring Boot app that loads the local DataFlow server. It is bound on port 9393

To interact with the dataflow server, you can download the dataflow shell provided by Spring.

Using the shell

Run the shell via:

java -jar spring-cloud-dataflow-shell-[version].RELEASE.jar

# Import apps
app import --uri http://bit.ly/stream-applications-rabbit-maven

# list apps available - (soures, processors, sinks, tasks)
app list

# Create a stream that reads from a file directory and writes to reservation-service
stream create --name files-to-reservations --definition " file --file.consumer.mode=lines --file.directory
=/path/to/directory > :reservations " --deploy

This will create a File directory source and hook up to the reservation service sink already configured, on 'reservations' RabbitMQ queue.