util: Add a jvm shutdown hook to call app.quit()

Differential Revision: https://phabricator.twitter.biz/D1236932

Author: Benjamin Erichsen

CHANGELOG.rst

@@ -25,7 +25,7 @@ Runtime Behavior Changes
   and stack trace are printed to stderr in addition to the existing stdout. ``PHAB_ID=D1116753``
 * util-jvm: Memory manager & pool metrics are labelled dimensionally rather than hierarchically
   when exported as dimensional metrics. ``PHAB_ID=D1218090``
-
+* util-app: Enables a jvm shutdown hook to call app.quit(). ``PHAB_ID=D1236932``
 
 23.11.0
 -------

util-app/src/main/scala/com/twitter/finagle/util/flags.scala

@@ -51,6 +51,6 @@ object loadServiceIgnoredPaths
  */
 object enableJvmShutdownHook
     extends GlobalFlag[Boolean](
-      false,
+      true,
       "Registers a JVM shutdown hook which invokes close()"
     )

util-app/src/test/scala/com/twitter/app/AppTest.scala

@@ -5,11 +5,13 @@ import com.twitter.app.lifecycle.Event
 import com.twitter.app.lifecycle.Observer
 import com.twitter.app.LoadService.Binding
 import com.twitter.conversions.DurationOps._
+import com.twitter.finagle.util.enableJvmShutdownHook
 import com.twitter.util._
 import java.util.concurrent.ConcurrentLinkedQueue
 import scala.jdk.CollectionConverters._
 import scala.language.reflectiveCalls
 import org.scalatest.funsuite.AnyFunSuite
+import org.scalatest.BeforeAndAfterEach
 
 class TestApp(f: () => Unit) extends App {
   var reason: Option[String] = None
@@ -61,7 +63,12 @@ trait ErrorOnExitApp extends App {
   }
 }
 
-class AppTest extends AnyFunSuite {
+class AppTest extends AnyFunSuite with BeforeAndAfterEach {
+
+  override protected def beforeEach(): Unit = {
+    enableJvmShutdownHook.parse("false")
+  }
+
   test("App: make sure system.exit called on exception from main") {
     val test1 = new TestApp(() => throw new RuntimeException("simulate main failing"))