Scala Jetty webapp on Heroku 404

Question

I'm testing around with a Scala web framework (Udash) and trying to run a toy-example in Heroku. I have it running without issues in local following the instructions in the Heroku docs:

sbt compile stage
heroku local web

However, once deployed, any URL I type goes to 404, even the landing page of the app. These are the objects I am using:

object Launcher extends CrossLogging {
  def main(args: Array[String]): Unit = {
    val port = Properties.envOrElse("PORT", "5000").toInt
    val server = new ApplicationServer(port, "frontend/target/UdashStatics/WebContent")
    server.start()
    logger.info(s"Application started...")
  }
}

class ApplicationServer(val port: Int, resourceBase: String) {
  private val server = new Server(port)
  private val contextHandler = new ServletContextHandler
  private val appHolder = createAppHolder()

  contextHandler.setSessionHandler(new SessionHandler)
  contextHandler.setGzipHandler(new GzipHandler)
  contextHandler.getSessionHandler.addEventListener(new org.atmosphere.cpr.SessionSupport())
  contextHandler.addServlet(appHolder, "/*")
  server.setHandler(contextHandler)

  def start(): Unit = server.start()
  def stop(): Unit = server.stop()

  private def createAppHolder() = {
    val appHolder = new ServletHolder(new DefaultServlet)
    appHolder.setAsyncSupported(true)
    appHolder.setInitParameter("resourceBase", resourceBase)
    appHolder
  }
}

Is there any Heroku configuration/characteristic that I am missing?

EDIT

Tried to apply the changes suggested and ended up with the following ApplicationContext:

class ApplicationServer(val port: Int, val resourceBase: String) {
  val server = new Server()
  val connector = new ServerConnector(server)
  connector.setPort(port)
  server.addConnector(connector)
  private val appHolder = createAppHolder()

  val context = new ServletContextHandler(ServletContextHandler.SESSIONS)

  context.setBaseResource(Resource.newResource(resourceBase))
  context.setContextPath("/")
  context.addServlet(appHolder, "/")
  server.setHandler(context)

  private def createAppHolder() = {
    val appHolder = new ServletHolder("default", classOf[DefaultServlet])
    appHolder.setInitParameter("dirAllowed", "true")
    appHolder.setInitParameter("resourceBase", resourceBase)
    appHolder
  }

  def start(): Unit = server.start()
  def stop(): Unit = server.stop()
}

However, I still get Error 404 even on landing page after deploying to Heroku:

HTTP ERROR 404
Problem accessing /. Reason:
    Not Found

When running the app on local I get to the landing page correctly.

Thank you! Thanks!

Answer 1

A few things to adjust that might help you.

1. resourceBase as a init-parameter on DefaultServlet is for alternate static file serving.
2. Use ServletContextHandler.setBaseResource(Resource) instead.
3. Use Resource.newResource(String) to create a new Resource reference. This should be an absolute path on the filesystem, or an absolute URI reference. no relative paths or URI fragments.
4. The DefaultServlet must be on the url-pattern of "/", not "/*" (this is a servlet spec requirement)
5. The DefaultServlet must be named, and must have the name "default" (this is a servlet spec requirement, see link on point 1 for example)
6. set the ServletContextHandler.setContextPath("/") to be explicit about what base context-path you want to use.

Some observations:

Your example code will only serve static content out of the resourceBase.

Since you have no welcomeFiles configured it would serve <resourceBase>/index.html by default (if you don't specify a specific static resource you want to access)

You have a SessionListener setup (org.atmosphere.cpr.SessionSupport), but since there's nothing that would access a Session, that code is pretty much a no-op.

There's no dynamic results from a custom Servlet or Filter present in your example codebase.