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News feed microservice in Scala on Vert.x

This version of the news feed service is written in Scala using the Vert.x framework. Another big difference between this implementation and the previous implementations is that this is designed in a style known as reactive programming. I covered this microservice implementation in my blog on Writing Reactive Microservices for the JVM.

Building

This is a typical scala project using the scala built tool.

sbt
compile
test

Deving

You can run this locally but be sure to set the environment variables to indicate where the dependent data stores are. You will also need to edit the src/main/resources/application.conf file to use 127.0.0.1 instead of mysql for the mysql host.

kubectl port-forward deployment/cassandra 9042:9042 &
export NOSQL_HOST=127.0.0.1
kubectl port-forward deployment/mysql 3306:3306 &
kubectl port-forward deployment/redis 6379:6379 &
export CACHE_HOST=127.0.0.1
kubectl port-forward deployment/elasticsearch 9200:9200 & 
export SEARCH_HOST=127.0.0.1
sbt
> console
scala> vertx.deployVerticle(nameForVerticle[info.glennengstrand.news.HttpVerticle])

From here you can freely interact with the Vert.x API inside the sbt-scala-shell. You can also call the API endpoints at http://127.0.0.1:8080 for testing the service itself.

Building the Uber Jar

To create the runnable uber jar use:

sbt assembly

Building the Docker Image

The project also contains everything you need to build the Docker container. Simply run the following commands to package your uber jar inside a Docker container

sbt docker
docker tag default/feed11:latest feed11:1.0

The ../k8s/feed11-deployment.yaml file contains the manifest for running this image. You will need to edit this file in order to run what you just built.

Static Code Analysis

Average per file lines of code is 42.33 with a median of 33 and a standard deviation of 33.58. The single unit test scala file is the largest with 200 lines of code. Total McCabe cyclomatic complexity is 1,300.

Load Test Results

Average per minute throughput of outbound posts is 14,136. Mean latency is 5.3 ms. Median latency is 5 ms, 95th percentile is 11 ms and 99th percentile is 15 ms. Resource utilization leveled at about 400 MB RAM and a little under a half CPU utilization.