sandbox: On initialization error, actually print the error and stop. (#4239)

Three problems here:

1. On failure, the Sandbox didn't close down the metrics reporting
thread, meaning the application would hang.
2. If there's a failure:
  a. we didn't print it, and
  b. we didn't exit with the correct status code.

These are now handled.

CHANGELOG_BEGIN
- [Sandbox] On initialization error, report the error correctly and exit
  with a status code of 1. Previously, the program would hang
  indefinitely. (This regression was introduced in v0.13.41.)
CHANGELOG_END

Co-authored-by: Samir Talwar <samir.talwar@digitalasset.com>

ledger/sandbox/src/main/scala/com/digitalasset/platform/sandbox/SandboxMain.scala

@@ -26,12 +26,19 @@ object SandboxMain extends App {
       if (closed.compareAndSet(false, true)) server.close()
     }
 
+    server.failure.foreach { exception =>
+      logger.error(
+        s"Shutting down Sandbox application due to an initialization error:\n${exception.getMessage}")
+      sys.exit(1)
+    }
+
     try {
       Runtime.getRuntime.addShutdownHook(new Thread(() => closeServer()))
     } catch {
-      case NonFatal(t) =>
-        logger.error("Shutting down Sandbox application because of initialization error", t)
+      case NonFatal(exception) =>
+        logger.error("Shutting down Sandbox application due to an initialization error.", exception)
         closeServer()
+        sys.exit(1)
     }
   }
 

ledger/sandbox/src/main/scala/com/digitalasset/platform/sandbox/SandboxServer.scala

@@ -113,12 +113,26 @@ final class SandboxServer(config: => SandboxConfig) extends AutoCloseable {
   private val authService: AuthService = config.authService.getOrElse(AuthServiceWildcard)
 
   private val metrics = new MetricRegistry
-  private val metricsReporting =
-    new MetricsReporting(metrics, "com.digitalasset.platform.sandbox")
 
   @volatile private var sandboxState: Resource[SandboxState] = _
 
-  sandboxState = start()(DirectExecutionContext)
+  sandboxState = {
+    implicit val executionContext: ExecutionContext = DirectExecutionContext
+    for {
+      _ <- ResourceOwner
+        .forCloseable(() => new MetricsReporting(metrics, getClass.getPackage.getName))
+        .acquire()
+      state <- start()
+    } yield state
+  }
+
+  def failure: Option[Throwable] =
+    Await
+      .result(
+        sandboxState.asFuture.transformWith(Future.successful)(DirectExecutionContext),
+        AsyncTolerance)
+      .failed
+      .toOption
 
   def port: Int =
     Await.result(portF(DirectExecutionContext), AsyncTolerance)
@@ -307,7 +321,6 @@ final class SandboxServer(config: => SandboxConfig) extends AutoCloseable {
   }
 
   override def close(): Unit = {
-    metricsReporting.close()
     Await.result(
       sandboxState.flatMap(_.apiServer)(DirectExecutionContext).release(),
       AsyncTolerance)