how to define multi-project build with sbt-native-packager that creates an RPM for each sub-project - sbt

Question

In all of the examples I've seen regarding multi-module builds and sbt-native-packager, they all aggregate the sub-projects into a single package. I have sub-projects that each provide a micro-service. I believe that each of these should have it's own native package, but I don't see how to do that and have a one command build for all of the sub-projects.

Answer 1

This turns out be straightforward. Simply provide native-packager settings for each of the sub-projects that you want to package and don't provide any on the aggregating project.
I tested by modifying https://github.com/muuki88/sbt-native-packager-examples/tree/master/multi-module-build accordingly:
import NativePackagerKeys._
name := "mukis-fullstack"
// used like the groupId in maven
organization in ThisBuild := "de.mukis"
// all sub projects have the same version
version in ThisBuild := "1.0"
scalaVersion in ThisBuild := "2.11.2"
// common dependencies
libraryDependencies in ThisBuild ++= Seq(
"com.typesafe" % "config" % "1.2.0"
)
// this is the root project, aggregating all sub projects
lazy val root = Project(
id = "root",
base = file("."),
// configure your native packaging settings here
// settings = packageArchetype.java_server++ Seq(
// maintainer := "John Smith <john.smith#example.com>",
// packageDescription := "Fullstack Application",
// packageSummary := "Fullstack Application",
// entrypoint
// mainClass in Compile := Some("de.mukis.frontend.ProductionServer")
// ),
// always run all commands on each sub project
aggregate = Seq(frontend, backend, api)
) dependsOn(frontend, backend, api) // this does the actual aggregation
// --------- Project Frontend ------------------
lazy val frontend = Project(
id = "frontend",
base = file("frontend"),
settings = packageArchetype.java_server++ Seq(
maintainer := "John Smith <john.smith#example.com>",
packageDescription := "Frontend appplication",
mainClass in Compile := Some("de.mukis.frontend.ProductionServer")
)
) dependsOn(api)
// --------- Project Backend ----------------
lazy val backend = Project(
id = "backend",
base = file("backend"),
settings = packageArchetype.java_server++ Seq(
maintainer := "John Smith <john.smith#example.com>",
packageDescription := "Fullstack Application",
packageSummary := "Fullstack Application",
// entrypoint
mainClass in Compile := Some("de.mukis.frontend.ProductionServer")
)
) dependsOn(api)
// --------- Project API ------------------
lazy val api = Project(
id = "api",
base = file("api")
Results:
debian:packageBin
...misc messages elided...
[info] dpkg-deb: building package `frontend' in `../frontend_1.0_all.deb'.
[info] dpkg-deb: building package `backend' in `../backend_1.0_all.deb'.

Answer 2

For whom just ended up here, a more up-to-date answer could look like:
lazy val root = (project in file("."))
.aggregate(common, frontend, backend)
lazy val common = (project in file("common"))
lazy val frontend = (project in file("frontend"))
.enablePlugins(JavaServerAppPackaging)
lazy val backend = (project in file("backend"))
.dependsOn(common)
.enablePlugins(JavaAppPackaging)
.settings(javaPackagingSettings)
lazy val javaPackagingSettings = Seq(
// follow sbt-native-packager to identify settings you need
)
Description
Here is the scenario supporting the above configuration
Project root is the parent and we don't want to package it. It aggregates other subprojects.
Project common is a sort of library and also we don't want to package it
Project backend depends on common for the libraries.
Project frontend is a standalone project packaged as a Java server app with default configuration