General

PoC for a GraphQL microservice. Explore Scala 3, particularly braceless syntax.

Following capabilities:

• Scala 3 (braceless)
• Federation support
• Handle n+1 queries problem
• Query ClickHouse
  • Custom decoders for CH datatypes
  • Automatic decoding to Scala types
• Maybe distributed tracing
• Maybe caching with Redis
• Maybe GraalVM native image compilation
• Maybe runnable image using GraalVM native image

Stack:

• zio
• zio-prelude (newtypes)
• zio-config
• jedis (redis client, gave up on zio-redis due to missing multi support)
• zio-telemetry with opentelemtry sdk (distributed tracing)
• caliban (GraphQL+federation support)
• zquery (n+1 problem)
• tranzactio with anorm (zio wrapper for anorm)
• anorm (Query ClickHouse with nice decoding)
• sbt-tpolecat for scalac configuration

Run locally

Local JVM

• Start ch docker container (cd docker && docker-compose start)
  • Init test data once when ch is up, run init script docker/insert-ch-data.sh
• Run sbt run

Native image

• Publish app native image sbt docker:publishLocal
• Start ch docker container and app native image container (cd docker && docker-compose --profile app start)
  • Init test data once when ch is up, run init script docker/insert-ch-data.sh

Example request

curl --location 'http://localhost:8080/api/graphql' \
--header 'Content-Type: application/json' \
--data '{"query":"query {\n    persons {\n        persons {\n            name\n            address {\n                street\n            }\n        }\n    }\n}","variables":{}}'

Native image

sbt-native-packager docker plugin can be used to create a runnable image ´sbt docker:publishLocal`.

Compile using a container

Compile native image in a container sbt graalvm-native-image:packageBin.

Compile locally

• Remove graalVMNativeImageGraalVersion := Some("22.3.2") from build.sbt
• Provide correct path -H:ConfigurationFileDirectories in build.sbt
• Provide native-image in PATH
• Run sbt graalvm-native-image:packageBin

Above tested with graalvm-ce-java17-22.3.2.

Endpoints

Http server @ localhost:8080

Endpoint	Description
/api/graphql	GraphQL api
/graphiql	GraphiQL
/metrics	Prometheus metrics
/health/liveness	Liveness
/health/readiness	Readiness