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news feed microservice on play and scala

This is another implementation of the news feed microservice written in Scala on the Play Framework. This project started from the example project for Making a REST API in Play. I covered this microservice implementation in my blog on Writing Reactive Microservices for the JVM.


How to develop on this service. You need to download and install sbt for this application to run.

Unit Tests

This command will run the unit tests.

sbt test

Running Locally

Either running locally or load testing locally, you will need to set up port forwarding so that the service can access the back end data sources.

kubectl port-forward deployment/cassandra 9042:9042 &
export NOSQL_HOST=
kubectl port-forward deployment/mysql 3306:3306 &
kubectl port-forward deployment/redis 6379:6379 &
export CACHE_HOST=
kubectl port-forward deployment/elasticsearch 9200:9200 & 

The following at the command prompt will start up Play in development mode:

sbt "run 8080"

Play will start up on the HTTP port at http://localhost:8080/. You don't need to deploy or reload anything -- changing any source code while the server is running will automatically recompile and hot-reload the application on the next HTTP request.

Load Testing

The best way to see what Play can do is to run a load test. We've included Gatling in this test project for integrated load testing.

Start Play in production mode, by staging the application and running the play script.

sbt stage
cd target/universal/stage
./bin/news-feed-play -Dplay.http.secret.key=LGG7q:ZHimG613xJXWL50cwgJ:nx6soU:XcPj2MhJ;GR[F0]ag:90cqpJ_ 

Then you'll start the Gatling load test up (it's already integrated into the project):

sbt ";project gatling;gatling:test"

Once the test completes, you'll see an HTML file containing the load test chart.

Build and Release

To be run in Kubernetes.

sbt dist
cd target/universal
cd ../..
docker build -t feed12:1.0 .

Static Code Analysis

Average per file Lines of Code is 55.48 with a median of 51 and a standard deviation of 32.92. The news action builder scala file (mostly boilerplate) is the largest with 123 LoC but the unit tests file is a close second at 122 LoC. Total McCabe cyclomatic complexity is 1,764.

Load Test Results

Play can be configured to run with a choice of two server backend technologies, either akka http or netty. Here are the per minute outbound post performance results for both. Throughput is in requests per minute. The other columns measure average and percentile based latency in milliseconds.

backend throughput mean median 95th 99th
akka 14,255 3.3 3 6 9
netty 20,151 4.4 4 8 11